CAP Profiles

Bio

Bio

Dr. Hargreaves is Professor of Radiology, with a research focus on body magnetic resonance imaging (MRI). He completed his PhD at Stanford University in Electrical Engineering before moving to the Radiology Department in 2005. He directs the Body MRI research group, which develops and implements new MRI techniques with the goal of improving patient care. His group's contributions affect hundreds of patients each year at Stanford and in other imaging centers around the world. In addition to research, Dr. Hargreaves teaches two graduate level courses, and lectures in numerous other courses at Stanford. He is a Fellow of the International Society for Magnetic Resonance in Medicine, where he served as chair of the Web Editorial Board and on the Board of Trustees for 5 years.

Academic Appointments

Administrative Appointments

  • Associate Chair, Research, Radiology (2018 - Present)

Honors & Awards

  • Basic Scientist Faculty of the Year, Stanford Radiology (Dec 2018)
  • Fellow of the Society of Breast MRI, SBMR (May 2018)
  • Fellow of the International Society for Magnetic Resonance in Medicine, ISMRM (June 2015)
  • Biodesign Mentorship Award, Stanford Biodesign (June 2015)
  • Distinguished Investigator, Association of Radiology Research (Dec 2014)
  • John Charnley Award, The Hip Society (Feb 2013)
  • Outstanding Teacher Award, ISMRM (May 2013)
  • Edward C. Nagy New Investigator, NIH / NIBIB (April 2011)
  • Thought Leader Award, GE Healthcare (May 2010)

Boards, Advisory Committees, Professional Organizations

  • Editorial Board, Magnetic Resonance in Medicine (2014 - Present)
  • Board of Trustees, ISMRM (2013 - 2018)
  • Chair, Web Editorial Board, ISMRM (2013 - 2018)

Professional Education

  • Ph.D., Stanford University, Electrical Engineering (2001)
  • M.S., Stanford University, Electrical Engineering (1997)
  • B.A.Sc, Simon Fraser University, Engineering Science (1994)

Contact

Links

Research & Scholarship

Current Research and Scholarly Interests

I am interested in magnetic resonance imaging (MRI) applications including cardiovascular, abdominal, breast and musculoskeletal imaging. These applications require development of faster and more efficient MRI methods that provide improved diagnostic contrast compared with current methods. My work includes novel excitation schemes, efficient imaging methods and reconstruction tools. Please see my research site (above) for most up-to-date information.

Clinical Trials

  • High Resolution 3D Diffusion-weighted Breast MRI Not Recruiting

    The purpose of this study is to determine how well a new MRI technique called "High resolution 3D diffusion-weighted breast MRI" detects breast cancer.

    Stanford is currently not accepting patients for this trial. For more information, please contact Sumita Sood, 650-723-0618.

    View full details

  • Magnetic Resonance Imaging of Breast Cancer Recruiting

    To compare magnetic resonance imaging (MRI) with more well established diagnostic imaging techniques to determine which method best finds and defines breast cancer.

    View full details

Teaching

2018-19 Courses

Stanford Advisees

Publications

All Publications

  • Combined 5-minute double-echo in steady-state with separated echoes and 2-minute proton-density-weighted 2D FSE sequence for comprehensive whole-joint knee MRI assessment. Journal of magnetic resonance imaging : JMRI Chaudhari, A. S., Stevens, K. J., Sveinsson, B., Wood, J. P., Beaulieu, C. F., Oei, E. H., Rosenberg, J. K., Kogan, F., Alley, M. T., Gold, G. E., Hargreaves, B. A. 2018

    Abstract

    BACKGROUND: Clinical knee MRI protocols require upwards of 15 minutes of scan time.PURPOSE/HYPOTHESIS: To compare the imaging appearance of knee abnormalities depicted with a 5-minute 3D double-echo in steady-state (DESS) sequence with separate echo images, with that of a routine clinical knee MRI protocol. A secondary goal was to compare the imaging appearance of knee abnormalities depicted with 5-minute DESS paired with a 2-minute coronal proton-density fat-saturated (PDFS) sequence.STUDY TYPE: Prospective.SUBJECTS: Thirty-six consecutive patients (19 male) referred for a routine knee MRI.FIELD STRENGTH/SEQUENCES: DESS and PDFS at 3T.ASSESSMENT: Five musculoskeletal radiologists evaluated all images for the presence of internal knee derangement using DESS, DESS+PDFS, and the conventional imaging protocol, and their associated diagnostic confidence of the reading.STATISTICAL TESTS: Differences in positive and negative percent agreement (PPA and NPA, respectively) and 95% confidence intervals (CIs) for DESS and DESS+PDFS compared with the conventional protocol were calculated and tested using exact McNemar tests. The percentage of observations where DESS or DESS+PDFS had equivalent confidence ratings to DESS+Conv were tested with exact symmetry tests. Interreader agreement was calculated using Krippendorff's alpha.RESULTS: DESS had a PPA of 90% (88-92% CI) and NPA of 99% (99-99% CI). DESS+PDFS had increased PPA of 99% (95-99% CI) and NPA of 100% (99-100% CI) compared with DESS (both P < 0.001). DESS had equivalent diagnostic confidence to DESS+Conv in 94% of findings, whereas DESS+PDFS had equivalent diagnostic confidence in 99% of findings (both P < 0.001). All readers had moderate concordance for all three protocols (Krippendorff's alpha 47-48%).DATA CONCLUSION: Both 1) 5-minute 3D-DESS with separated echoes and 2) 5-minute 3D-DESS paired with a 2-minute coronal PDFS sequence depicted knee abnormalities similarly to a routine clinical knee MRI protocol, which may be a promising technique for abbreviated knee MRI.LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

    View details for DOI 10.1002/jmri.26582

    View details for PubMedID 30582251

  • Accelerated imaging of metallic implants using model-based nonlinear reconstruction. Magnetic resonance in medicine Shi, X., Levine, E., Weber, H., Hargreaves, B. A. 2018

    Abstract

    PURPOSE: To accelerate imaging near metallic implants with multi-spectral imaging (MSI) techniques by exploiting a signal model in the spectral dimension.METHODS: MSI techniques resolve metal-induced field perturbations by acquiring separate 3D spatial encodings at multiple excitation frequencies, which are referred to as spectral bins. The proposed model-based reconstruction exploits the correlation between spectral bins in image reconstruction by enforcing a signal model to describe the signal profile across bins. This work evaluates the accuracy of the MSI signal model in simulations and in vivo experiments. The proposed model-based reconstruction was evaluated in 6 subjects at an overall undersampling factor of 17.4 and compared with model-free parallel imaging and compressed sensing (PI & CS). The quality of reconstructed images was evaluated using normalized RMS error (nRMSE) and structural similarity index (SSIM) comparisons, with paired Wilcoxon tests in 6 subjects used to determine whether there was a significant difference in the metrics.RESULTS: Both simulations and in vivo experiments show that the proposed signal model can represent the MSI signal profiles in the spectral dimension compactly and accurately. In the in vivo experiments, the model-based reconstruction significantly improved image quality over model-free PI & CS, with P < 0.05 for both nRMSE and SSIM at 17.4* acceleration.CONCLUSION: This work presents the feasibility of using a model-based reconstruction to accelerate MSI techniques for faster MR imaging near metal.

    View details for DOI 10.1002/mrm.27536

    View details for PubMedID 30515853

  • View-Sharing Artifact Reduction With Retrospective Compressed Sensing Reconstruction in the Context of Contrast-Enhanced Liver MRI for Hepatocellular Carcinoma (HCC) Screening. Journal of magnetic resonance imaging : JMRI Shaikh, J., Stoddard, P. B., Levine, E. G., Roh, A. T., Saranathan, M., Chang, S. T., Muelly, M. C., Hargreaves, B. A., Vasanawala, S. S., Loening, A. M. 2018

    Abstract

    BACKGROUND: View-sharing (VS) increases spatiotemporal resolution in dynamic contrast-enhanced (DCE) MRI by sharing high-frequency k-space data across temporal phases. This temporal sharing results in respiratory motion within any phase to propagate artifacts across all shared phases. Compressed sensing (CS) eliminates the need for VS by recovering missing k-space data from pseudorandom undersampling, reducing temporal blurring while maintaining spatial resolution.PURPOSE: To evaluate a CS reconstruction algorithm on undersampled DCE-MRI data for image quality and hepatocellular carcinoma (HCC) detection.STUDY TYPE: Retrospective.SUBJECTS: Fifty consecutive patients undergoing MRI for HCC screening (29 males, 21 females, 52-72 years).FIELD STRENGTH/SEQUENCE: 3.0T MRI. Multiphase 3D-SPGR T1 -weighted sequence undersampled in arterial phases with a complementary Poisson disc sampling pattern reconstructed with VS and CS algorithms.ASSESSMENT: VS and CS reconstructions evaluated by blinded assessments of image quality and anatomic delineation on Likert scales (1-4 and 1-5, respectively), and HCC detection by OPTN/UNOS criteria including a diagnostic confidence score (1-5). Blinded side-by-side reconstruction comparisons for lesion depiction and overall series preference (-3-3).STATISTICAL ANALYSIS: Two-tailed Wilcoxon signed rank tests for paired nonparametric analyses with Bonferroni-Holm multiple-comparison corrections. McNemar's test for differences in lesion detection frequency and transplantation eligibility.RESULTS: CS compared with VS demonstrated significantly improved contrast (mean 3.6 vs. 2.9, P<0.0001) and less motion artifact (mean 3.6 vs. 3.2, P=0.006). CS compared with VS demonstrated significantly improved delineations of liver margin (mean 4.5 vs. 3.8, P=0.0002), portal veins (mean 4.5 vs. 3.7, P<0.0001), and hepatic veins (mean 4.6 vs. 3.5, P<0.0001), but significantly decreased delineation of hepatic arteries (mean 3.2 vs. 3.7, P=0.004). No significant differences were seen in the other assessments.DATA CONCLUSION: Applying a CS reconstruction to data acquired for a VS reconstruction significantly reduces motion artifacts in a clinical DCE protocol for HCC screening.LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

    View details for DOI 10.1002/jmri.26276

    View details for PubMedID 30390358

  • Motion-robust reconstruction of multishot diffusion-weighted images without phase estimation through locally low-rank regularization. Magnetic resonance in medicine Hu, Y., Levine, E. G., Tian, Q., Moran, C. J., Wang, X., Taviani, V., Vasanawala, S. S., McNab, J. A., Daniel, B. A., Hargreaves, B. L. 2018

    Abstract

    PURPOSE: The goal of this work is to propose a motion robust reconstruction method for diffusion-weighted MRI that resolves shot-to-shot phase mismatches without using phase estimation.METHODS: Assuming that shot-to-shot phase variations are slowly varying, spatial-shot matrices can be formed using a local group of pixels to form columns, in which each column is from a different shot (excitation). A convex model with a locally low-rank constraint on the spatial-shot matrices is proposed. In vivo brain and breast experiments were performed to evaluate the performance of the proposed method.RESULTS: The proposed method shows significant benefits when the motion is severe, such as for breast imaging. Furthermore, the resulting images can be used for reliable phase estimation in the context of phase-estimation-based methods to achieve even higher image quality.CONCLUSION: We introduced the shot-locally low-rank method, a reconstruction technique for multishot diffusion-weighted MRI without explicit phase estimation. In addition, its motion robustness can be beneficial to neuroimaging and body imaging.

    View details for DOI 10.1002/mrm.27488

    View details for PubMedID 30346058

  • Fast Intensity Non-Uniformity Correction for MR Images Using Sparse Samples Shi, L., Perkins, S., Moran, C., Hargreaves, B., Daniel, B. WILEY. 2018: E360

    View details for Web of Science ID 000434978002187

  • Internal Breast Tumor Heterogeneity On T2-Weighted Imaging: Double Echo Steady State(DESS) Versus 3D Fast Spin Echo (CUBE) Shi, L., Alley, M., Hargreaves, B., Daniel, B., Moran, C. WILEY. 2018: E192

    View details for Web of Science ID 000434978000279

  • Super-resolution musculoskeletal MRI using deep learning. Magnetic resonance in medicine Chaudhari, A. S., Fang, Z., Kogan, F., Wood, J., Stevens, K. J., Gibbons, E. K., Lee, J. H., Gold, G. E., Hargreaves, B. A. 2018

    Abstract

    PURPOSE: To develop a super-resolution technique using convolutional neural networks for generating thin-slice knee MR images from thicker input slices, and compare this method with alternative through-plane interpolation methods.METHODS: We implemented a 3D convolutional neural network entitled DeepResolve to learn residual-based transformations between high-resolution thin-slice images and lower-resolution thick-slice images at the same center locations. DeepResolve was trained using 124 double echo in steady-state (DESS) data sets with 0.7-mm slice thickness and tested on 17 patients. Ground-truth images were compared with DeepResolve, clinically used tricubic interpolation, and Fourier interpolation methods, along with state-of-the-art single-image sparse-coding super-resolution. Comparisons were performed using structural similarity, peak SNR, and RMS error image quality metrics for a multitude of thin-slice downsampling factors. Two musculoskeletal radiologists ranked the 3 data sets and reviewed the diagnostic quality of the DeepResolve, tricubic interpolation, and ground-truth images for sharpness, contrast, artifacts, SNR, and overall diagnostic quality. Mann-Whitney U tests evaluated differences among the quantitative image metrics, reader scores, and rankings. Cohen's Kappa (kappa) evaluated interreader reliability.RESULTS: DeepResolve had significantly better structural similarity, peak SNR, and RMS error than tricubic interpolation, Fourier interpolation, and sparse-coding super-resolution for all downsampling factors (p<.05, except 4*and 8*sparse-coding super-resolution downsampling factors). In the reader study, DeepResolve significantly outperformed (p<.01) tricubic interpolation in all image quality categories and overall image ranking. Both readers had substantial scoring agreement (kappa=0.73).CONCLUSION: DeepResolve was capable of resolving high-resolution thin-slice knee MRI from lower-resolution thicker slices, achieving superior quantitative and qualitative diagnostic performance to both conventionally used and state-of-the-art methods.

    View details for DOI 10.1002/mrm.27178

    View details for PubMedID 29582464

  • Accelerated three-dimensional multispectral MRI with robust principal component analysis for separation of on- and off-resonance signals MAGNETIC RESONANCE IN MEDICINE Levine, E., Stevens, K., Beaulieu, C., Hargreaves, B. 2018; 79 (3): 1495–1505

    Abstract

    To enable highly accelerated distortion-free MRI near metal by separating on- and off-resonance to exploit the redundancy of slice-phase encoding for the dominant on-resonance component.Multispectral MRI techniques resolve off-resonance distortions by a combination of limited excitation bins and additional encoding. Inspired by robust principal component analysis, a novel compact representation of multispectral images as a sum of rank-one and sparse matrices corresponding to on- and off-resonance respectively is described. This representation is used in a calibration-free and model-free reconstruction for data with an undersampling pattern that varies between bins. Retrospective undersampling was used to compare the proposed reconstruction and bin-by-bin compressed sensing. Hip images were acquired in eight patients with standard and prospectively undersampled three-dimensional multispectral imaging, and image quality was evaluated by two radiologists on a 5-point scale.Experiments with retrospective undersampling showed that the enhanced sparsity afforded by the separation greatly reduces reconstruction errors and artifacts. Images from prospectively undersampled multispectral imaging offered 2.6-3.4-fold (18-24-fold overall) acceleration compared to standard multispectral imaging with parallel imaging and partial-Fourier acceleration with equivalence in all qualitative assessments within a tolerance of one point (P < 0.004).Three-dimensional multispectral imaging can be highly accelerated by varying undersampling between bins and separating on- and off-resonance. Magn Reson Med 79:1495-1505, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26819

    View details for Web of Science ID 000427184700026

    View details for PubMedID 28686800

    View details for PubMedCentralID PMC5756705

  • On-the-Fly Adaptive k-Space Sampling for Linear MRI Reconstruction Using Moment-Based Spectral Analysis IEEE TRANSACTIONS ON MEDICAL IMAGING Levine, E., Hargreaves, B. 2018; 37 (2): 557–67

    Abstract

    In high-dimensional magnetic resonance imaging applications, time-consuming, sequential acquisition of data samples in the spatial frequency domain ( -space) can often be accelerated by accounting for dependencies in linear reconstruction, at the cost of noise amplification that depends on the sampling pattern. Common examples are support-constrained, parallel, and dynamic MRI, and -space sampling strategies are primarily driven by image-domain metrics that are expensive to compute for arbitrary sampling patterns. It remains challenging to provide systematic and computationally efficient automatic designs of arbitrary multidimensional Cartesian sampling patterns that mitigate noise amplification, given the subspace to which the object is confined. To address this problem, this paper introduces a theoretical framework that describes local geometric properties of the sampling pattern and relates them to the spread in the eigenvalues of the information matrix described by its first two spectral moments. This new criterion is then used for very efficient optimization of complex multidimensional sampling patterns that does not require reconstructing images or explicitly mapping noise amplification. Experiments with in vivo data show strong agreement between this criterion and traditional, comprehensive image-domain- and -space-based metrics, indicating the potential of the approach for computationally efficient (on-the-fly), automatic, and adaptive design of sampling patterns.

    View details for DOI 10.1109/TMI.2017.2766131

    View details for Web of Science ID 000424467000021

    View details for PubMedID 29408784

    View details for PubMedCentralID PMC5840375

  • Fat-based registration of breast dynamic contrast enhanced water images. Magnetic resonance in medicine Srinivasan, S., Hargreaves, B. A., Daniel, B. L. 2018; 79 (4): 2408–14

    Abstract

    In this study, a 3D fat-based deformable registration algorithm was developed for registering dynamic contrast-enhanced breast images.The mutual information similarity measure with free-form deformation motion correction in rapidly enhancing lesions can introduce motion. However, in Dixon-based fat-water separated acquisitions, the nonenhancing fat signal can directly be used to estimate deformable motion, which can be later used to deform the water images. Qualitative comparison of the fat-based registration method to a water-based registration method, and to the unregistered images, was performed by two experienced readers. Quantitative analysis of the registration was evaluated by estimating the mean-squared signal difference on the fat images.Using a scale of 0 (no motion) to 2 ( > 4 voxels of motion), the average image quality score of the fat-based registered images was 0.5 ± 0.6, water-based registration was 0.8 ± 0.8, and the unregistered dataset was 1.6 ± 0.6. The mean-squared-signal-difference metric on the fat images was significantly lower for fat-based registered images compared with both water-based registered and unregistered images.Fat-based registration of breast dynamic contrast-enhanced images is a promising technique for performing deformable motion correction of breast without introducing new motion. Magn Reson Med 79:2408-2414, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26851

    View details for PubMedID 28745402

  • Quantitative imaging of bone-cartilage interactions in ACL-injured patients with PET-MRI. Osteoarthritis and cartilage Kogan, F., Fan, A. P., Monu, U., Iagaru, A., Hargreaves, B. A., Gold, G. E. 2018

    Abstract

    To investigate changes in bone metabolism by positron emission tomography (PET), as well as spatial relationships between bone metabolism and magnetic resonance imaging (MRI) quantitative markers of early cartilage degradation, in anterior cruciate ligament (ACL)-reconstructed knees.Both knees of 15 participants with unilateral reconstructed ACL tears and unaffected contralateral knees were scanned using a simultaneous 3.0T PET-MRI system following injection of 18F-sodium fluoride (18F-NaF). The maximum pixel standardized uptake value (SUVmax) in the subchondral bone and the average T2 relaxation time in cartilage were measured in each knee in eight knee compartments. We tested differences in SUVmax and cartilage T2 relaxation times between the ACL-injured knee and the contralateral control knee as well as spatial relationships between these bone and cartilage changes.Significantly increased subchondral bone 18F-NaF SUVmax and cartilage T2 times were observed in the ACL-reconstructed knees (median [inter-quartile-range (IQR)]: 5.0 [5.8], 36.8 [3.6] ms) compared to the contralateral knees (median [IQR]: 1.9 [1.4], 34.4 [3.8] ms). A spatial relationship between the two markers was also seen. Using the contralateral knee as a control, we observed a significant correlation of r = 0.59 between the difference in subchondral bone SUVmax (between injured and contralateral knees) and the adjacent cartilage T2 (between the two knees) [P < 0.001], with a slope of 0.49 ms/a.u. This correlation and slope were higher in deep layers (r = 0.73, slope = 0.60 ms/a.u.) of cartilage compared to superficial layers (r = 0.40, slope = 0.43 ms/a.u.).18F-NaF PET-MR imaging enables detection of increased subchondral bone metabolism in ACL-reconstructed knees and may serve as an important marker of early osteoarthritis (OA) progression. Spatial relationships observed between early OA changes across bone and cartilage support the need to study whole-joint disease mechanisms in OA.

    View details for DOI 10.1016/j.joca.2018.04.001

    View details for PubMedID 29656143

  • Imaging of magnetic ink patterns via off-resonance sensitivity. Magnetic resonance in medicine Perkins, S. L., Daniel, B. L., Hargreaves, B. A. 2018

    Abstract

    Printed magnetic ink creates predictable B0 field perturbations based on printed shape and magnetic susceptibility. This can be exploited for contrast in MR imaging techniques that are sensitized to off-resonance. The purpose of this work was to characterize the susceptibility variations of magnetic ink and demonstrate its application for creating MR-visible skin markings.The magnetic susceptibility of the ink was estimated by comparing acquired and simulated B0 field maps of a custom-built phantom. The phantom was also imaged using a 3D gradient echo sequence with a presaturation pulse tuned to different frequencies, which adjusts the range of suppressed frequencies. Healthy volunteers with a magnetic ink pattern pressed to the skin or magnetic ink temporary flexible adhesives applied to the skin were similarly imaged.The volume-average magnetic susceptibility of the ink was estimated to be 131 ± 3 parts per million across a 1-mm isotropic voxel (13,100 parts per million assuming a 10-μm thickness of printed ink). Adjusting the saturation frequency highlights different off-resonant regions created by the ink patterns; for example, if tuned to suppress fat, fat suppression will fail near the ink due to the off-resonance. This causes magnetic ink skin markings placed over a region with underlying subcutaneous fat to be visible on MR images.Patterns printed with magnetic ink can be imaged and identified with MRI. Temporary flexible skin adhesives printed with magnetic ink have the potential to be used as skin markings that are visible both by eye and on MR images.

    View details for DOI 10.1002/mrm.27187

    View details for PubMedID 29603366

  • The impact of computed high b-value images on the diagnostic accuracy of DWI for prostate cancer: A receiver operating characteristics analysis. Scientific reports Ning, P., Shi, D., Sonn, G. A., Vasanawala, S. S., Loening, A. M., Ghanouni, P., Obara, P., Shin, L. K., Fan, R. E., Hargreaves, B. A., Daniel, B. L. 2018; 8 (1): 3409

    Abstract

    To evaluate the performance of computed high b value diffusion-weighted images (DWI) in prostate cancer detection. 97 consecutive patients who had undergone multiparametric MRI of the prostate followed by biopsy were reviewed. Five radiologists independently scored 138 lesions on native high b-value images (b = 1200 s/mm2), apparent diffusion coefficient (ADC) maps, and computed high b-value images (contrast equivalent to b = 2000 s/mm2) to compare their diagnostic accuracy. Receiver operating characteristic (ROC) analysis and McNemar's test were performed to assess the relative performance of computed high b value DWI, native high b-value DWI and ADC maps. No significant difference existed in the area under the curve (AUC) for ROCs comparing B1200 (b = 1200 s/mm2) to computed B2000 (c-B2000) in 5 readers. In 4 of 5 readers c-B2000 had significantly increased sensitivity and/or decreased specificity compared to B1200 (McNemar's p < 0.05), at selected thresholds of interpretation. ADC maps were less accurate than B1200 or c-B2000 for 2 of 5 readers (P < 0.05). This study detected no consistent improvement in overall diagnostic accuracy using c-B2000, compared with B1200 images. Readers detected more cancer with c-B2000 images (increased sensitivity) but also more false positive findings (decreased specificity).

    View details for DOI 10.1038/s41598-018-21523-6

    View details for PubMedID 29467370

    View details for PubMedCentralID PMC5821845

  • Artifact-reduced imaging of biopsy needles with 2D multispectral imaging. Magnetic resonance in medicine Weber, H., Hargreaves, B. A., Daniel, B. L. 2018; 80 (2): 655–61

    Abstract

    Magnetic resonance (MR) guidance for biopsy procedures requires high intrinsic soft-tissue contrast. However, artifacts induced by the metallic needle can reduce its localization and require low-susceptibility needle materials with poorer cutting performance. In a proof of concept, we demonstrate the feasibility of 2D multispectral imaging (2DMSI) for both needle tracking and for needle artifact reduction for more precise needle localization and to enable the usage of needle materials with higher susceptibility.We applied 2DMSI for imaging of MR-compatible biopsy needles, conventional stainless-steel needles, and mixed-material needles and compared it to conventional techniques. In addition, we exploited intrinsic off-resonance information for passive needle tracking.2DMSI achieved a stronger reduction of the needle artifact compared to conventional techniques. For the mixed-material needles, the artifact was reduced to a level below that for MR-compatible needles with conventional imaging. The passive tracking also improved the ability to pinpoint the needle.2DMSI is promising for both needle tracking and artifact-reduced imaging of biopsy needles for a more precise needle localization. 2DMSI may be particularly promising for needles inducing large distortions or for targeting of small lesions. In addition, it may enable the use of needle materials with higher susceptibility and potentially better sampling performance. Magn Reson Med 80:655-661, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.27056

    View details for PubMedID 29285787

    View details for PubMedCentralID PMC5910245

  • Simultaneous bilateral-knee MR imaging. Magnetic resonance in medicine Kogan, F., Levine, E., Chaudhari, A. S., Monu, U. D., Epperson, K., Oei, E. H., Gold, G. E., Hargreaves, B. A. 2018; 80 (2): 529–37

    Abstract

    To demonstrate and evaluate the scan time and quantitative accuracy of simultaneous bilateral-knee imaging compared with single-knee acquisitions.Hardware modifications and safety testing was performed to enable MR imaging with two 16-channel flexible coil arrays. Noise covariance and sensitivity-encoding g-factor maps for the dual-coil-array configuration were computed to evaluate coil cross-talk and noise amplification. Ten healthy volunteers were imaged on a 3T MRI scanner with both dual-coil-array bilateral-knee and single-coil-array single-knee configurations. Two experienced musculoskeletal radiologists compared the relative image quality between blinded image pairs acquired with each configuration. Differences in T2 relaxation time measurements between dual-coil-array and single-coil-array acquisitions were compared with the standard repeatability of single-coil-array measurements using a Bland-Altman analysis.The mean g-factors for the dual-coil-array configuration were low for accelerations up to 6 in the right-left direction, and minimal cross-talk was observed between the two coil arrays. Image quality ratings of various joint tissues showed no difference in 89% (95% confidence interval: 85-93%) of rated image pairs, with only small differences ("slightly better" or "slightly worse") in image quality observed. The T2 relaxation time measurements between the dual-coil-array configuration and the single-coil configuration showed similar limits of agreement and concordance correlation coefficients (limits of agreement: -0.93 to 1.99 ms; CCC: 0.97 (95% confidence interval: 0.96-0.98)), to the repeatability of single-coil-array measurements (limits of agreement: -2.07 to 1.96 ms; CCC: 0.97 (95% confidence interval: 0.95-0.98)).A bilateral coil-array setup can image both knees simultaneously in similar scan times as conventional unilateral knee scans, with comparable image quality and quantitative accuracy. This has the potential to improve the value of MRI knee evaluations. Magn Reson Med 80:529-537, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.27045

    View details for PubMedID 29250856

    View details for PubMedCentralID PMC5910219

  • MRI monitoring of focused ultrasound sonications near metallic hardware. Magnetic resonance in medicine Weber, H., Ghanouni, P., Pascal-Tenorio, A., Pauly, K. B., Hargreaves, B. A. 2018; 80 (1): 259–71

    Abstract

    To explore the temperature-induced signal change in two-dimensional multi-spectral imaging (2DMSI) for fast thermometry near metallic hardware to enable MR-guided focused ultrasound surgery (MRgFUS) in patients with implanted metallic hardware.2DMSI was optimized for temperature sensitivity and applied to monitor focus ultrasound surgery (FUS) sonications near metallic hardware in phantoms and ex vivo porcine muscle tissue. Further, we evaluated its temperature sensitivity for in vivo muscle in patients without metallic hardware. In addition, we performed a comparison of temperature sensitivity between 2DMSI and conventional proton-resonance-frequency-shift (PRFS) thermometry at different distances from metal devices and different signal-to-noise ratios (SNR).2DMSI thermometry enabled visualization of short ultrasound sonications near metallic hardware. Calibration using in vivo muscle yielded a constant temperature sensitivity for temperatures below 43 °C. For an off-resonance coverage of ± 6 kHz, we achieved a temperature sensitivity of 1.45%/K, resulting in a minimum detectable temperature change of ∼2.5 K for an SNR of 100 with a temporal resolution of 6 s per frame.The proposed 2DMSI thermometry has the potential to allow MR-guided FUS treatments of patients with metallic hardware and therefore expand its reach to a larger patient population. Magn Reson Med 80:259-271, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.27034

    View details for PubMedID 29215150

    View details for PubMedCentralID PMC5876098

  • Anatomical Road Mapping Using CT and MR Enterography for Ultrasound Molecular Imaging of Small Bowel Inflammation in Swine. European radiology Wang, H., Felt, S. A., Guracar, I., Taviani, V., Zhou, J., Sigrist, R. M., Zhang, H., Liau, J., Vilches-Moure, J. G., Tian, L., Saenz, Y., Bettinger, T., Hargreaves, B. A., Lutz, A. M., Willmann, J. K. 2018; 28 (5): 2068–76

    Abstract

    To evaluate the feasibility and time saving of fusing CT and MR enterography with ultrasound for ultrasound molecular imaging (USMI) of inflammation in an acute small bowel inflammation of swine.Nine swine with ileitis were scanned with either CT (n = 3) or MR (n = 6) enterography. Imaging times to load CT/MR images onto a clinical ultrasound machine, fuse them to ultrasound with an anatomical landmark-based approach, and identify ileitis were compared to the imaging times without anatomical road mapping. Inflammation was then assessed by USMI using dual selectin-targeted (MBSelectin) and control (MBControl) contrast agents in diseased and healthy control bowel segments, followed by ex vivo histology.Cross-sectional image fusion with ultrasound was feasible with an alignment error of 13.9 ± 9.7 mm. Anatomical road mapping significantly reduced (P < 0.001) scanning times by 40%. Localising ileitis was achieved within 1.0 min. Subsequently performed USMI demonstrated significantly (P < 0.001) higher imaging signal using MBSelectin compared to MBControl and histology confirmed a significantly higher inflammation score (P = 0.006) and P- and E-selectin expression (P ≤ 0.02) in inflamed vs. healthy bowel.Fusion of CT and MR enterography data sets with ultrasound in real time is feasible and allows rapid anatomical localisation of ileitis for subsequent quantification of inflammation using USMI.• Real-time fusion of CT/MRI with ultrasound to localise ileitis is feasible. • Anatomical road mapping using CT/MRI significantly decreases the scanning time for USMI. • USMI allows quantification of inflammation in swine, verified with ex vivo histology.

    View details for DOI 10.1007/s00330-017-5148-6

    View details for PubMedID 29170798

  • Five-minute knee MRI for simultaneous morphometry and T2 relaxometry of cartilage and meniscus and for semiquantitative radiological assessment using double-echo in steady-state at 3T. Journal of magnetic resonance imaging : JMRI Chaudhari, A. S., Black, M. S., Eijgenraam, S., Wirth, W., Maschek, S., Sveinsson, B., Eckstein, F., Oei, E. H., Gold, G. E., Hargreaves, B. A. 2018; 47 (5): 1328–41

    Abstract

    Biomarkers for assessing osteoarthritis activity necessitate multiple MRI sequences with long acquisition times.To perform 5-minute simultaneous morphometry (thickness/volume measurements) and T2 relaxometry of both cartilage and meniscus, and semiquantitative MRI Osteoarthritis Knee Scoring (MOAKS).Prospective.Fifteen healthy volunteers for morphometry and T2 measurements, and 15 patients (five each Kellgren-Lawrence grades 0/2/3) for MOAKS assessment.A 5-minute double-echo steady-state (DESS) sequence was evaluated for generating quantitative and semiquantitative osteoarthritis biomarkers at 3T.Flip angle simulations evaluated tissue signals and sensitivity of T2 measurements. Morphometry and T2 reproducibility was compared against morphometry-optimized and relaxometry-optimized sequences. Repeatability was assessed by scanning five volunteers twice. MOAKS reproducibility was compared to MOAKS derived from a clinical knee MRI protocol by two readers.Coefficients of variation (CVs), concordance confidence intervals (CCI), and Wilcoxon signed-rank tests compared morphometry and relaxometry measurements with their reference standards. DESS MOAKS positive percent agreement (PPA), negative percentage agreement (NPA), and interreader agreement was calculated using the clinical protocol as a reference. Biomarker variations between Kellgren-Lawrence groups were evaluated using Wilcoxon rank-sum tests.Cartilage thickness (P = 0.65), cartilage T2 (P = 0.69), and meniscus T2 (P = 0.06) did not significantly differ from their reference standard (with a 20° DESS flip angle). DESS slightly overestimated meniscus volume (P < 0.001). Accuracy and repeatability CVs were <3.3%, except the meniscus T2 accuracy (7.6%). DESS MOAKS had substantial interreader agreement and high PPA/NPA values of 87%/90%. Bone marrow lesions and menisci had slightly lower PPAs. Cartilage and meniscus T2 , and MOAKS (cartilage surface area, osteophytes, cysts, and total score) was higher in Kellgren-Lawrence groups 2 and 3 than group 0 (P < 0.05).The 5-minute DESS sequence permits MOAKS assessment for a majority of tissues, along with repeatable and reproducible simultaneous cartilage and meniscus T2 relaxometry and morphometry measurements.2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1328-1341.

    View details for DOI 10.1002/jmri.25883

    View details for PubMedID 29090500

    View details for PubMedCentralID PMC5899635

  • Mitigation of near-band balanced steady-state free precession through-plane flow artifacts using partial dephasing. Magnetic resonance in medicine Datta, A., Cheng, J. Y., Hargreaves, B. A., Baron, C. A., Nishimura, D. G. 2018; 79 (6): 2944–53

    Abstract

    To mitigate artifacts from through-plane flow at the locations of steady-state stopbands in balanced steady-state free precession (SSFP) using partial dephasing.A 60° range in the phase accrual during a TR was created over the voxel by slightly unbalancing the slice-select dephaser. The spectral profiles of SSFP with partial dephasing for various constant flow rates and during pulsatile flow were simulated to determine if partial dephasing decreases through-plane flow artifacts originating near SSFP dark bands while maintaining on-resonant signal. Simulations were then validated in a flow phantom. Lastly, phase-cycled SSFP cardiac cine images were acquired with and without partial dephasing in six subjects.Partial dephasing decreased the strength and non-linearity of the dependence of the signal at the stopbands on the through-plane flow rate. It thus mitigated hyper-enhancement from out-of-slice signal contributions and transient-related artifacts caused by variable flow both in the phantom and in vivo. In six volunteers, partial dephasing noticeably decreased artifacts in all of the phase-cycled cardiac cine datasets.Partial dephasing can mitigate the flow artifacts seen at the stopbands in balanced SSFP while maintaining the sequence's desired signal. By mitigating hyper-enhancement and transient-related artifacts originating from the stopbands, partial dephasing facilitates robust multiple-acquisition phase-cycled SSFP in the heart. Magn Reson Med 79:2944-2953, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26957

    View details for PubMedID 28994486

  • Self-Calibrating Wave-Encoded Variable-Density Single-Shot Fast Spin Echo Imaging. Journal of magnetic resonance imaging : JMRI Chen, F., Taviani, V., Tamir, J. I., Cheng, J. Y., Zhang, T., Song, Q., Hargreaves, B. A., Pauly, J. M., Vasanawala, S. S. 2018; 47 (4): 954–66

    Abstract

    It is highly desirable in clinical abdominal MR scans to accelerate single-shot fast spin echo (SSFSE) imaging and reduce blurring due to T2 decay and partial-Fourier acquisition.To develop and investigate the clinical feasibility of wave-encoded variable-density SSFSE imaging for improved image quality and scan time reduction.Prospective controlled clinical trial.With Institutional Review Board approval and informed consent, the proposed method was assessed on 20 consecutive adult patients (10 male, 10 female, range, 24-84 years).A wave-encoded variable-density SSFSE sequence was developed for clinical 3.0T abdominal scans to enable high acceleration (3.5×) with full-Fourier acquisitions by: 1) introducing wave encoding with self-refocusing gradient waveforms to improve acquisition efficiency; 2) developing self-calibrated estimation of wave-encoding point-spread function and coil sensitivity to improve motion robustness; and 3) incorporating a parallel imaging and compressed sensing reconstruction to reconstruct highly accelerated datasets.Image quality was compared pairwise with standard Cartesian acquisition independently and blindly by two radiologists on a scale from -2 to 2 for noise, contrast, confidence, sharpness, and artifacts. The average ratio of scan time between these two approaches was also compared.A Wilcoxon signed-rank tests with a P value under 0.05 considered statistically significant.Wave-encoded variable-density SSFSE significantly reduced the perceived noise level and improved the sharpness of the abdominal wall and the kidneys compared with standard acquisition (mean scores 0.8, 1.2, and 0.8, respectively, P < 0.003). No significant difference was observed in relation to other features (P = 0.11). An average of 21% decrease in scan time was achieved using the proposed method.Wave-encoded variable-density sampling SSFSE achieves improved image quality with clinically relevant echo time and reduced scan time, thus providing a fast and robust approach for clinical SSFSE imaging.1 Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2018;47:954-966.

    View details for DOI 10.1002/jmri.25853

    View details for PubMedID 28906567

  • Automatic renal segmentation for MR urography using 3D-GrabCut and random forests. Magnetic resonance in medicine Yoruk, U., Hargreaves, B. A., Vasanawala, S. S. 2018; 79 (3): 1696–1707

    Abstract

    To introduce and evaluate a fully automated renal segmentation technique for glomerular filtration rate (GFR) assessment in children.An image segmentation method based on iterative graph cuts (GrabCut) was modified to work on time-resolved 3D dynamic contrast-enhanced MRI data sets. A random forest classifier was trained to further segment the renal tissue into cortex, medulla, and the collecting system. The algorithm was tested on 26 subjects and the segmentation results were compared to the manually drawn segmentation maps using the F1-score metric. A two-compartment model was used to estimate the GFR of each subject using both automatically and manually generated segmentation maps.Segmentation maps generated automatically showed high similarity to the manually drawn maps for the whole-kidney (F1 = 0.93) and renal cortex (F1 = 0.86). GFR estimations using whole-kidney segmentation maps from the automatic method were highly correlated (Spearman's ρ = 0.99) to the GFR values obtained from manual maps. The mean GFR estimation error of the automatic method was 2.98 ± 0.66% with an average segmentation time of 45 s per patient.The automatic segmentation method performs as well as the manual segmentation for GFR estimation and reduces the segmentation time from several hours to 45 s. Magn Reson Med 79:1696-1707, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26806

    View details for PubMedID 28656614

    View details for PubMedCentralID PMC5745323

  • Metallic Implant Geometry and Susceptibility Estimation Using Multispectral B-0 Field Maps MAGNETIC RESONANCE IN MEDICINE Shi, X., Yoon, D., Koch, K. M., Hargreaves, B. A. 2017; 77 (6): 2402-2413

    Abstract

    To estimate the susceptibility and the geometry of metallic implants from multispectral imaging (MSI) information, to separate the metal implant region from the surrounding signal loss region.The susceptibility map of signal-void regions is estimated from MSI B0 field maps using total variation (TV) regularized inversion. Voxels with susceptibility estimates above a predetermined threshold are identified as metal. The accuracy of the estimated susceptibility and implant geometry was evaluated in simulations, phantom, and in vivo experiments.The proposed method provided more accurate susceptibility estimation compared with a previous method without TV regularization, in both simulations and phantom experiments. In the phantom experiment where the actual implant was 40% of the signal-void region, the mean estimated susceptibility was close to the susceptibility in literature, and the precision and recall of the estimated geometry was 85% and 93%. In vivo studies in subjects with hip implants also demonstrated that the proposed method can distinguish implants from surrounding low-signal tissues, such as cortical bone.The proposed method can improve the delineation of metallic implant geometry by distinguishing metal voxels from artificial signal voids and low-signal tissues by estimating the susceptibility maps. Magn Reson Med 77:2402-2413, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26313

    View details for Web of Science ID 000401270900031

  • Multispectral diffusion-weighted imaging near metal implants. Magnetic resonance in medicine Koch, K. M., Bhave, S., Gaddipati, A., Hargreaves, B. A., Gui, D., Peters, R., Bedi, M., Mannem, R., Kaushik, S. S. 2017

    Abstract

    The need for diffusion-weighted-imaging (DWI) near metallic implants is becoming increasingly relevant for a variety of clinical diagnostic applications. Conventional DWI methods are significantly hindered by metal-induced image artifacts. A novel approach relying on multispectral susceptibility artifact reduction techniques is presented to address this unmet need.DWI near metal implants is achieved through a combination of several advanced MRI acquisition technologies. Previously described approaches to Carr-Purcell-Meiboom-Gill spin-echo train DWI sequences using the periodically rotated overlapping parallel lines with enhanced reconstruction are combined with multispectral-imaging metal artifact reduction principles to provide DWI with substantially reduced artifact levels. The presented methods are applied to limited sets of slices over areas of sarcoma risk near six implanted devices.Using the presented methods, DWI assessment without bulk image distortions is demonstrated in the immediate vicinity of metallic interfaces. In one subject, the apparent diffusion coefficient was reduced in a region of suspected sarcoma directly adjacent to fixation hardware.An initial demonstration of minimal-artifact multispectral DWI in the near vicinity of metallic hardware is described and successfully demonstrated on clinical subjects. Magn Reson Med 79:987-993, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26737

    View details for PubMedID 28470795

  • 3D Cartesian MRI with compressed sensing and variable view sharing using complementary poisson-disc sampling MAGNETIC RESONANCE IN MEDICINE Levine, E., Daniel, B., Vasanawala, S., Hargreaves, B., Saranathan, M. 2017; 77 (5): 1774-1785

    Abstract

    To enable robust, high spatio-temporal-resolution three-dimensional Cartesian MRI using a scheme incorporating a novel variable density random k-space sampling trajectory allowing flexible and retrospective selection of the temporal footprint with compressed sensing (CS).A complementary Poisson-disc k-space sampling trajectory was designed to allow view sharing and varying combinations of reduced view sharing with CS from the same prospective acquisition. These schemes were used for two-point Dixon-based dynamic contrast-enhanced MRI (DCE-MRI) of the breast and abdomen. Results were validated in vivo with a novel approach using variable-flip-angle data, which was retrospectively accelerated using the same methods but offered a ground truth.In breast DCE-MRI, the temporal footprint could be reduced 2.3-fold retrospectively without introducing noticeable artifacts, improving depiction of rapidly enhancing lesions. Further, experiments with variable-flip-angle data showed that reducing view sharing improved accuracy in reconstruction and T1 mapping. In abdominal MRI, 2.3-fold and 3.6-fold reductions in temporal footprint allowed reduced motion artifacts.The complementary-Poisson-disc k-space sampling trajectory allowed a retrospective spatiotemporal resolution tradeoff using CS and view sharing, imparting robustness to motion and contrast enhancement. The technique was also validated using a novel approach of fully acquired variable-flip-angle acquisition. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.26254

    View details for Web of Science ID 000399666400005

    View details for PubMedCentralID PMC5074926

  • Resolving phase ambiguity in dual-echo dixon imaging using a projected power method MAGNETIC RESONANCE IN MEDICINE Zhang, T., Chen, Y., Bao, S., Alley, M. T., Pauly, J. M., Hargreaves, B. A., Vasanawala, S. S. 2017; 77 (5): 2066-2076

    Abstract

    To develop a fast and robust method to resolve phase ambiguity in dual-echo Dixon imaging.A major challenge in dual-echo Dixon imaging is to estimate the phase error resulting from field inhomogeneity. In this work, a binary quadratic optimization program was formulated to resolve the phase ambiguity. A projected power method was developed to efficiently solve the optimization problem. Both the 1-peak fat model and 6-peak fat model were applied to three-dimensional (3D) datasets. Additionally, the proposed method was extended to dynamic magnetic resonance imaging (MRI) applications using the 6-peak fat model. With institutional review board (IRB) approval and patient consent/assent, the proposed method was evaluated and compared with region growing on 29 consecutive 3D high-resolution patient datasets.Fast and robust water/fat separation was achieved by the proposed method in different representative 3D datasets and dynamic 3D datasets. Superior water/fat separation was achieved using the 6-peak fat model compared with the 1-peak fat model. Compared to region growing, the proposed method reduced water/fat swaps from 76 to 7% of the patient cohort.The proposed method can achieve fast and robust phase error estimation in dual-echo Dixon imaging. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.26287

    View details for Web of Science ID 000399666400034

    View details for PubMedCentralID PMC5123983

  • A simple analytic method for estimating T2 in the knee from DESS MAGNETIC RESONANCE IMAGING Sveinsson, B., Chaudhari, A. S., Gold, G. E., Hargreaves, B. A. 2017; 38: 63-70

    Abstract

    To introduce a simple analytical formula for estimating T2 from a single Double-Echo in Steady-State (DESS) scan.Extended Phase Graph (EPG) modeling was used to develop a straightforward linear approximation of the relationship between the two DESS signals, enabling accurate T2 estimation from one DESS scan. Simulations were performed to demonstrate cancellation of different echo pathways to validate this simple model. The resulting analytic formula was compared to previous methods for T2 estimation using DESS and fast spin-echo scans in agar phantoms and knee cartilage in three volunteers and three patients. The DESS approach allows 3D (256×256×44) T2-mapping with fat suppression in scan times of 3-4min.The simulations demonstrated that the model approximates the true signal very well. If the T1 is within 20% of the assumed T1, the T2 estimation error was shown to be less than 5% for typical scans. The inherent residual error in the model was demonstrated to be small both due to signal decay and opposing signal contributions. The estimated T2 from the linear relationship agrees well with reference scans, both for the phantoms and in vivo. The method resulted in less underestimation of T2 than previous single-scan approaches, with processing times 60 times faster than using a numerical fit.A simplified relationship between the two DESS signals allows for rapid 3D T2 quantification with DESS that is accurate, yet also simple. The simplicity of the method allows for immediate T2 estimation in cartilage during the MRI examination.

    View details for DOI 10.1016/j.mri.2016.12.018

    View details for Web of Science ID 000398008700010

    View details for PubMedCentralID PMC5360502

  • 2D multi-spectral imaging for fast MRI near metal. Magnetic resonance in medicine Hargreaves, B. A., Taviani, V., Litwiller, D. V., Yoon, D. 2017

    Abstract

    To develop a fast 2D method for MRI near metal with reduced B0 in-plane and through-slice artifacts.Multi-spectral imaging (MSI) approaches reduce artifacts in MR images near metal, but require 3D imaging of multiple excited volumes regardless of imaging geometry or artifact severity. The proposed 2D MSI method rapidly excites a limited slice and spectral region using gradient reversal between excitation and refocusing pulses, then uses standard 2D imaging, with the process repeating to cover multiple spectral offsets that are combined as in other MSI techniques. 2D MSI was implemented in a spin-echo-train sequence and validated in phantoms and in vivo by comparing it with standard spin-echo imaging and existing MSI techniques.2D MSI images for each spatial-spectral region follow isocontours of the dipole-like B0 field variation, and thus frequency variation, near metal devices. Artifact correction in phantoms and human subjects with metal is comparable to 3D MSI methods, and superior to standard spin-echo techniques. Scan times are reduced compared with 3D MSI methods in cases where a limited number of slices are needed, though signal-to-noise ratio is also reduced as expected.2D MSI offers a fast and flexible alternative to 3D MSI for artifact reduction near metal. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26724

    View details for PubMedID 28444805

  • Cluster analysis of quantitative MRI T-2 and T-1 rho relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T OSTEOARTHRITIS AND CARTILAGE Monu, U. D., Jordan, C. D., Samuelson, B. L., Hargreaves, B. A., Gold, G. E., McWalter, E. J. 2017; 25 (4): 513-520

    Abstract

    To identify focal lesions of elevated MRI T2 and T1ρ relaxation times in articular cartilage of an ACL-injured group using a novel cluster analysis technique.Eighteen ACL-injured patients underwent 3T MRI T2 and T1ρ relaxometry at baseline, 6 months and 1 year and six healthy volunteers at baseline, 1 day and 1 year. Clusters of contiguous pixels above or below T2 and T1ρ intensity and area thresholds were identified on a projection map of the 3D femoral cartilage surface. The total area of femoral cartilage plate covered by clusters (%CA) was split into areas above (%CA+) and below (%CA-) the thresholds and the differences in %CA(+ or -) over time in the ACL-injured group were determined using the Wilcoxon signed rank test.%CA+ was greater in the ACL-injured patients than the healthy volunteers at 6 months and 1 year with average %CA+ of 5.2 ± 4.0% (p = 0.0054) and 6.6 ± 3.7% (p = 0.0041) for T2 and 6.2 ± 7.1% (p = 0.063) and 8.2 ± 6.9% (p = 0.042) for T1ρ, respectively. %CA- at 6 months and 1 year was 3.0 ± 1.8% (p > 0.1) and 5.9 ± 5.0% (p > 0.1) for T2 and 4.4 ± 4.9% (p > 0.1) and 4.5 ± 4.6% (p > 0.1) for T1ρ, respectively.With the proposed cluster analysis technique, we have quantified cartilage lesion coverage and demonstrated that the ACL-injured group had greater areas of elevated T2 and T1ρ relaxation times as compared to healthy volunteers.

    View details for DOI 10.1016/j.joca.2016.09.015

    View details for Web of Science ID 000401093200015

  • Improved field-mapping and artifact correction in multispectral imaging. Magnetic resonance in medicine Quist, B., Shi, X., Weber, H., Hargreaves, B. A. 2017

    Abstract

    To develop a method for improved B0 field-map estimation, deblurring, and image combination for multispectral imaging near metal.A goodness-of-fit field-map estimation technique is proposed that uses only the multispectral imaging (MSI) data to estimate the field map. Using the improved field map, a novel deblurring technique is proposed that also employs a new image combination scheme to reduce the effects of noise and other residual MSI artifacts. The proposed field-map estimation and deblurring techniques are compared to the current methods in phantoms and/or in vivo from subjects with knee, hip, and spinal metallic implants.Phantom experiments validate that the goodness-of-fit field-map estimation is less sensitive to noise and bias than the conventional center-of-mass technique, which reduces distortion in the deblurring methods. The new deblurring approach also is substantially less sensitive to noise and distortion than the current deblurring method, as demonstrated in phantoms and in vivo, and is able to find a good tradeoff between deblurring and distortion.The proposed methods not only enable field-mapping with reduced noise sensitivity but are able to create deblurred images with less distortion and better signal-to-noise ratio with no additional scan time, thereby enabling improved visualization of underlying anatomy near metallic implants. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26597

    View details for PubMedID 28261847

  • Volumetric Multislice GagCEST Imaging of Articular Cartilage: Optimization and Comparison With T1rho MAGNETIC RESONANCE IN MEDICINE Kogan, F., Hargreaves, B. A., Gold, G. E. 2017; 77 (3): 1134-1141

    Abstract

    To develop and optimize a multislice glycosaminoglycan (GAG) chemical exchange saturation transfer (GagCEST) sequence for volumetric imaging of articular cartilage, and to validate the sequence against T1ρ relaxation times in whole joint imaging of tibiotalar cartilage.Ex vivo experiments were used to observe the effect of the number of partitions and shot TR on signal-to-noise ratio and measured GagCESTasym . GagCEST imaging of the entire tibiotalar joint was also performed on 10 healthy subjects. The measured GagCESTasym was compared and correlated with T1ρ relaxation times.Ex vivo studies showed a higher average GagCESTasym from articular cartilage on multislice acquisitions acquired with two or more partitions than observed with a single-slice acquisition. In healthy human subjects, an average GagCESTasym of 8.8 ± 0.7% was observed. A coefficient of variation of GagCESTasym across slices of less than 15% was seen for all subjects. Across subjects, a Pearson correlation coefficient of -0.58 was observed between the measured gagCESTasym and T1ρ relaxation times.We demonstrated the feasibility and optimization of multislice GagCEST mapping of articular cartilage. Volumetric analysis and decreased scan times will help to advance the clinical utility of GagCEST imaging of articular cartilage. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.26200

    View details for Web of Science ID 000397407800022

  • MR Thermometry Near Metallic Devices Using Multispectral Imaging MAGNETIC RESONANCE IN MEDICINE Weber, H., Taviani, V., Yoon, D., Ghanouni, P., Pauly, K. B., Hargreaves, B. A. 2017; 77 (3): 1162-1169

    Abstract

    The lack of a technique for MR thermometry near metal excludes a growing patient population from promising treatments such as MR-guided focused ultrasound therapy. Here we explore the feasibility of multispectral imaging (MSI) for noninvasive temperature measurement in the presence of strong field inhomogeneities by exploiting the temperature dependency of the T1 relaxation time.A two-dimensional inversion-recovery-prepared MSI pulse sequence (2DMSI) was implemented for artifact-reduced T1 mapping near metal. A series of T1 maps was acquired in a metallic implant phantom while increasing the phantom temperature. The measured change in T1 was analyzed with respect to the phantom temperature. For comparison, proton resonance frequency shift (PRFS) thermometry was performed.2DMSI achieved artifact-reduced, single-slice T1 mapping in the presence of strong off-resonance with a spatial resolution of 1.9 mm in-plane and a temporal resolution of 5 min. The maps enabled temperature measurements over a range of 30°C with an uncertainty below 1.4°C. The quality of the resulting temperature maps was independent of the distance from the metal, whereas the PRFS-based temperature measurements were increasingly impaired with increasing off-resonance.We demonstrated the ability to noninvasively measure temperature near metal using MSI and the T1 temperature sensitivity. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.26203

    View details for Web of Science ID 000397407800025

  • connective tissues in the knee using ultrashort echo-time double-echo steady-state (UTEDESS). Magnetic resonance in medicine Chaudhari, A. S., Sveinsson, B., Moran, C. J., McWalter, E. J., Johnson, E. M., Zhang, T., Gold, G. E., Hargreaves, B. A. 2017

    Abstract

    To develop a radial, double-echo steady-state (DESS) sequence with ultra-short echo-time (UTE) capabilities for T2 measurement of short-T2 tissues along with simultaneous rapid, signal-to-noise ratio (SNR)-efficient, and high-isotropic-resolution morphological knee imaging.THe 3D radial UTE readouts were incorporated into DESS, termed UTEDESS. Multiple-echo-time UTEDESS was used for performing T2 relaxometry for short-T2 tendons, ligaments, and menisci; and for Dixon water-fat imaging. In vivo T2 estimate repeatability and SNR efficiency for UTEDESS and Cartesian DESS were compared. The impact of coil combination methods on short-T2 measurements was evaluated by means of simulations. UTEDESS T2 measurements were compared with T2 measurements from Cartesian DESS, multi-echo spin-echo (MESE), and fast spin-echo (FSE).UTEDESS produced isotropic resolution images with high SNR efficiency in all short-T2 tissues. Simulations and experiments demonstrated that sum-of-squares coil combinations overestimated short-T2 measurements. UTEDESS measurements of meniscal T2 were comparable to DESS, MESE, and FSE measurements while the tendon and ligament measurements were less biased than those from Cartesian DESS. Average UTEDESS T2 repeatability variation was under 10% in all tissues.The T2 measurements of short-T2 tissues and high-resolution morphological imaging provided by UTEDESS makes it promising for studying the whole knee, both in routine clinical examinations and longitudinal studies. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26577

    View details for PubMedID 28074498

  • High-resolution diffusion-weighted imaging of the breast with multiband 2D radiofrequency pulses and a generalized parallel imaging reconstruction MAGNETIC RESONANCE IN MEDICINE Taviani, V., Alley, M. T., Banerjee, S., Nishimura, D. G., Daniel, B. L., Vasanawala, S. S., Hargreaves, B. A. 2017; 77 (1): 209-220

    Abstract

    To develop a technique for high-resolution diffusion-weighted imaging (DWI) and to compare it with standard DWI methods.Multiple in-plane bands of magnetization were simultaneously excited by identically phase modulating each subpulse of a two-dimensional (2D) RF pulse. Several excitations with the same multiband pattern progressively shifted in the phase-encode direction were used to cover the prescribed field of view (FOV). The phase-encoded FOV was limited to the width of a single band to reduce off-resonance-induced distortion and blurring. Parallel imaging (PI) techniques were used to resolve aliasing from the other bands and to combine the different excitations. Following validation in phantoms and healthy volunteers, a preliminary study in breast cancer patients (N=14) was performed to compare the proposed method to conventional DWI with PI and to reduced-FOV DWI.The proposed method gave high-resolution diffusion-weighted images with minimal artifacts at the band intersections. Compared to PI alone, higher phase-encoded FOV-reduction factors and reduced noise amplification were obtained, which translated to higher resolution images than conventional (non-multiband) DWI. The same resolution and image quality achievable over targeted regions using existing reduced-FOV methods was obtained, but the proposed method also enables complete bilateral coverage.We developed an in-plane multiband technique for high-resolution DWI and compared its performance with other standard DWI methods. Magn Reson Med 77:209-220, 2017. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.26110

    View details for Web of Science ID 000391038800022

  • A Mixed-Reality System for Breast Surgical Planning Perkins, S. L., Lin, M. A., Srinivasan, S., Wheeler, A. J., Hargreaves, B. A., Daniel, B. L., Broll, W., Regenbrecht, H., Swan, J. E., Bruder, G., Servieres, M., Sugimoto, M. IEEE. 2017: 269–74

    View details for DOI 10.1109/ISMAR-Adjunct.2017.92

    View details for Web of Science ID 000425896400068

  • Feasibility of 7T MRI for Imaging Fascicular Structures of Peripheral Nerves. Muscle & nerve Yoon, D., Biswal, S., Rutt, B., Lutz, A., Hargreaves, B. 2017

    Abstract

    Evaluation of the nerve fascicular structure can be useful in diagnosing nerve damage, but it is a very challenging task with 3T MRI due to limited resolution. In this pilot study, we present the feasibility of high-resolution 7T MRI for examining the nerve fascicular structure.A 3D gradient-spoiled sequence was used for imaging peripheral nerves in extremities. Images acquired with different in-plane resolutions (0.42 x 0.42mm vs. 0.12 x 0.12mm), and different main field strengths (7T vs. 3T) were compared.The individual nerve fascicles were identified at 0.12 x 0.12mm resolution in both field strengths, but not at 0.42 x 0.42mm resolution. The fascicular structure was more sharply depicted in 7T images than in 3T images.High-resolution 3D imaging with 7T MRI demonstrated feasibility in imaging nerve fascicular structures. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/mus.26035

    View details for PubMedID 29211916

  • 18F-FDG PET/MRI in Chronic Sciatica: Early Results Revealing Spinal and Non-spinal Abnormalities. Journal of nuclear medicine : official publication, Society of Nuclear Medicine Cipriano, P., Yoon, D., Gandhi, H., Holley, D., Thakur, D., Ith, M., Hargreaves, B., Kennedy, D., Smuck, M., Cheng, I., Biswal, S. 2017

    Abstract

    Chronic sciatica is a major cause of disability worldwide, but accurate diagnosis of the offending pathology remains challenging. In this report, the feasibility of a fluorodeoxyglucose (18F-FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) approach for improved diagnosis of chronic sciatica is presented. Methods:18F-FDG PET/MRI was performed on 9 chronic sciatica patients and 5 healthy volunteers. Region-of-interest analysis using maximum standardized uptake values (SUVmax) was performed, and 18F-FDG uptake in lesions was compared with the corresponding areas in healthy controls. Results: Significantly increased 18F-FDG uptake was observed in detected lesions of all patients, which was correlated with pain symptoms. 18F-FDG-avid lesions were not only found in impinged spinal nerves, but were also associated with non-spinal causes, such as a facet joint degeneration, pars defect, or a presumed scar neuroma. Conclusion: The feasibility of 18F-FDG PET/MRI for diagnosing pain generators in chronic sciatica has been demonstrated, revealing various possible etiologies.

    View details for DOI 10.2967/jnumed.117.198259

    View details for PubMedID 29097408

  • Relative value of three whole-body MR approaches for PET-MR, including gadofosveset-enhanced MR, in comparison to PET-CT. Clinical imaging Obara, P., Loening, A., Taviani, V., Iagaru, A., Hargreaves, B. A., Vasanawala, S. 2017; 48: 62–68

    Abstract

    Evaluate MR protocol for PET-MR including coronal DWI (cDWI), fat-suppressed T2 (T2w), and gadofosveset-enhanced T1 (CE).18 patients underwent same-day PET-CT and PET-MR. Image quality and performance of each sequence, and combination of all three sequences, was evaluated with respect to PET-CT.Lesion conspicuity was best on cDWI, while delineation was best on CE. Considering all three sequences combined, both readers showed good sensitivity and specificity (>80%). Relative sensitivity was highest on CE and lowest on T2w.Whole-body MR performed well in detecting malignant lesions compared to PET-CT. CE showed overall highest performance.

    View details for DOI 10.1016/j.clinimag.2017.09.016

    View details for PubMedID 29031209

  • Cluster analysis of quantitative MRI T2 and T1? relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T. Osteoarthritis and cartilage Monu, U. D., JORDAN, C. D., Samuelson, B. L., Hargreaves, B. A., Gold, G. E., McWalter, E. J. 2016

    Abstract

    To identify focal lesions of elevated MRI T2 and T1ρ relaxation times in articular cartilage of an ACL-injured group using a novel cluster analysis technique.Eighteen ACL-injured patients underwent 3T MRI T2 and T1ρ relaxometry at baseline, 6 months and 1 year and six healthy volunteers at baseline, 1 day and 1 year. Clusters of contiguous pixels above or below T2 and T1ρ intensity and area thresholds were identified on a projection map of the 3D femoral cartilage surface. The total area of femoral cartilage plate covered by clusters (%CA) was split into areas above (%CA+) and below (%CA-) the thresholds and the differences in %CA(+ or -) over time in the ACL-injured group were determined using the Wilcoxon signed rank test.%CA+ was greater in the ACL-injured patients than the healthy volunteers at 6 months and 1 year with average %CA+ of 5.2 ± 4.0% (p = 0.0054) and 6.6 ± 3.7% (p = 0.0041) for T2 and 6.2 ± 7.1% (p = 0.063) and 8.2 ± 6.9% (p = 0.042) for T1ρ, respectively. %CA- at 6 months and 1 year was 3.0 ± 1.8% (p > 0.1) and 5.9 ± 5.0% (p > 0.1) for T2 and 4.4 ± 4.9% (p > 0.1) and 4.5 ± 4.6% (p > 0.1) for T1ρ, respectively.With the proposed cluster analysis technique, we have quantified cartilage lesion coverage and demonstrated that the ACL-injured group had greater areas of elevated T2 and T1ρ relaxation times as compared to healthy volunteers.

    View details for DOI 10.1016/j.joca.2016.09.015

    View details for PubMedID 27720806

  • A semiflexible 64-channel receive-only phased array for pediatric body MRI at 3T. Magnetic resonance in medicine Zhang, T., Grafendorfer, T., Cheng, J. Y., Ning, P., Rainey, B., Giancola, M., Ortman, S., Robb, F. J., Calderon, P. D., Hargreaves, B. A., Lustig, M., Scott, G. C., Pauly, J. M., Vasanawala, S. S. 2016; 76 (3): 1015-1021

    Abstract

    To design, construct, and validate a semiflexible 64-channel receive-only phased array for pediatric body MRI at 3T.A 64-channel receive-only phased array was developed and constructed. The designed flexible coil can easily conform to different patient sizes with nonoverlapping coil elements in the transverse plane. It can cover a field of view of up to 44 × 28 cm(2) and removes the need for coil repositioning for body MRI patients with multiple clinical concerns. The 64-channel coil was compared with a 32-channel standard coil for signal-to-noise ratio and parallel imaging performances on different phantoms. With IRB approval and informed consent/assent, the designed coil was validated on 21 consecutive pediatric patients.The pediatric coil provided higher signal-to-noise ratio than the standard coil on different phantoms, with the averaged signal-to-noise ratio gain at least 23% over a depth of 7 cm along the cross-section of phantoms. It also achieved better parallel imaging performance under moderate acceleration factors. Good image quality (average score 4.6 out of 5) was achieved using the developed pediatric coil in the clinical studies.A 64-channel semiflexible receive-only phased array has been developed and validated to facilitate high quality pediatric body MRI at 3T. Magn Reson Med 76:1015-1021, 2016. © 2015 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.25999

    View details for PubMedID 26418283

    View details for PubMedCentralID PMC4811745

  • field maps. Magnetic resonance in medicine Shi, X., Yoon, D., Koch, K. M., Hargreaves, B. A. 2016

    Abstract

    To estimate the susceptibility and the geometry of metallic implants from multispectral imaging (MSI) information, to separate the metal implant region from the surrounding signal loss region.The susceptibility map of signal-void regions is estimated from MSI B0 field maps using total variation (TV) regularized inversion. Voxels with susceptibility estimates above a predetermined threshold are identified as metal. The accuracy of the estimated susceptibility and implant geometry was evaluated in simulations, phantom, and in vivo experiments.The proposed method provided more accurate susceptibility estimation compared with a previous method without TV regularization, in both simulations and phantom experiments. In the phantom experiment where the actual implant was 40% of the signal-void region, the mean estimated susceptibility was close to the susceptibility in literature, and the precision and recall of the estimated geometry was 85% and 93%. In vivo studies in subjects with hip implants also demonstrated that the proposed method can distinguish implants from surrounding low-signal tissues, such as cortical bone.The proposed method can improve the delineation of metallic implant geometry by distinguishing metal voxels from artificial signal voids and low-signal tissues by estimating the susceptibility maps. Magn Reson Med 77:2402-2413, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

    View details for DOI 10.1002/mrm.26313

    View details for PubMedID 27385493

  • Resolving phase ambiguity in dual-echo dixon imaging using a projected power method. Magnetic resonance in medicine Zhang, T., Chen, Y., Bao, S., Alley, M. T., Pauly, J. M., Hargreaves, B. A., Vasanawala, S. S. 2016

    Abstract

    To develop a fast and robust method to resolve phase ambiguity in dual-echo Dixon imaging.A major challenge in dual-echo Dixon imaging is to estimate the phase error resulting from field inhomogeneity. In this work, a binary quadratic optimization program was formulated to resolve the phase ambiguity. A projected power method was developed to efficiently solve the optimization problem. Both the 1-peak fat model and 6-peak fat model were applied to three-dimensional (3D) datasets. Additionally, the proposed method was extended to dynamic magnetic resonance imaging (MRI) applications using the 6-peak fat model. With institutional review board (IRB) approval and patient consent/assent, the proposed method was evaluated and compared with region growing on 29 consecutive 3D high-resolution patient datasets.Fast and robust water/fat separation was achieved by the proposed method in different representative 3D datasets and dynamic 3D datasets. Superior water/fat separation was achieved using the 6-peak fat model compared with the 1-peak fat model. Compared to region growing, the proposed method reduced water/fat swaps from 76 to 7% of the patient cohort.The proposed method can achieve fast and robust phase error estimation in dual-echo Dixon imaging. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.26287

    View details for PubMedID 27221766

  • Combined parenchymal and vascular imaging: High spatiotemporal resolution arterial evaluation of hepatocellular carcinoma JOURNAL OF MAGNETIC RESONANCE IMAGING Hope, T. A., Petkovska, I., Saranathan, M., Hargreaves, B. A., Vasanawala, S. S. 2016; 43 (4): 859-865

    Abstract

    To assess the ability of high-resolution arterial phase imaging of hepatocellular carcinoma (HCC) to provide combined vascular characterization and parenchymal evaluation.Thirty-eight consecutive studies in cirrhotic patients with HCC scanned with a view-shared 2-point-Dixon-based Differential Subsampling with Cartesian Ordering (DISCO) sequence were analyzed. Lesion contrast relative to precontrast and adjacent parenchyma was evaluated and compared using a Fisher's exact test. Visibility of hepatic arteries and tumor feeding vessels were graded on a 5-point scale. Catheter angiography was used as a reference standard for arterial anatomy.The high spatiotemporal multiphasic acquisition allowed imaging of both the angiographic and late arterial phase in 30 of 38 studies with good image quality. Maximal lesion enhancement compared to precontrast occurred more frequently during the late arterial phase compared to maximal lesion-to-adjacent, which occurred more frequently during the early arterial phase (P < 0.001). Common and proper hepatic arteries were visualized adequately in 100%, right hepatic artery in 94-97%, left hepatic artery in 94%, and segmental vessel in 83% of cases. Arterial variants were detected with sensitivity of 87-100% and specificity of 100%.High spatiotemporal resolution arterial phase imaging provides multiple angiographic and arterial phases in a single breath-hold, enabling accurate depiction of vascular anatomy while maintain optimal arterial phase imaging for characterization of focal lesions. J. Magn. Reson. Imaging 2016;43:859-865.

    View details for DOI 10.1002/jmri.25042

    View details for Web of Science ID 000373000500009

  • Combined parenchymal and vascular imaging: High spatiotemporal resolution arterial evaluation of hepatocellular carcinoma. Journal of magnetic resonance imaging Hope, T. A., Petkovska, I., Saranathan, M., Hargreaves, B. A., Vasanawala, S. S. 2016; 43 (4): 859-865

    Abstract

    To assess the ability of high-resolution arterial phase imaging of hepatocellular carcinoma (HCC) to provide combined vascular characterization and parenchymal evaluation.Thirty-eight consecutive studies in cirrhotic patients with HCC scanned with a view-shared 2-point-Dixon-based Differential Subsampling with Cartesian Ordering (DISCO) sequence were analyzed. Lesion contrast relative to precontrast and adjacent parenchyma was evaluated and compared using a Fisher's exact test. Visibility of hepatic arteries and tumor feeding vessels were graded on a 5-point scale. Catheter angiography was used as a reference standard for arterial anatomy.The high spatiotemporal multiphasic acquisition allowed imaging of both the angiographic and late arterial phase in 30 of 38 studies with good image quality. Maximal lesion enhancement compared to precontrast occurred more frequently during the late arterial phase compared to maximal lesion-to-adjacent, which occurred more frequently during the early arterial phase (P < 0.001). Common and proper hepatic arteries were visualized adequately in 100%, right hepatic artery in 94-97%, left hepatic artery in 94%, and segmental vessel in 83% of cases. Arterial variants were detected with sensitivity of 87-100% and specificity of 100%.High spatiotemporal resolution arterial phase imaging provides multiple angiographic and arterial phases in a single breath-hold, enabling accurate depiction of vascular anatomy while maintain optimal arterial phase imaging for characterization of focal lesions. J. Magn. Reson. Imaging 2016;43:859-865.

    View details for DOI 10.1002/jmri.25042

    View details for PubMedID 26340309

  • MR thermometry near metallic devices using multispectral imaging. Magnetic resonance in medicine Weber, H., Taviani, V., Yoon, D., Ghanouni, P., Pauly, K. B., Hargreaves, B. A. 2016

    Abstract

    The lack of a technique for MR thermometry near metal excludes a growing patient population from promising treatments such as MR-guided focused ultrasound therapy. Here we explore the feasibility of multispectral imaging (MSI) for noninvasive temperature measurement in the presence of strong field inhomogeneities by exploiting the temperature dependency of the T1 relaxation time.A two-dimensional inversion-recovery-prepared MSI pulse sequence (2DMSI) was implemented for artifact-reduced T1 mapping near metal. A series of T1 maps was acquired in a metallic implant phantom while increasing the phantom temperature. The measured change in T1 was analyzed with respect to the phantom temperature. For comparison, proton resonance frequency shift (PRFS) thermometry was performed.2DMSI achieved artifact-reduced, single-slice T1 mapping in the presence of strong off-resonance with a spatial resolution of 1.9 mm in-plane and a temporal resolution of 5 min. The maps enabled temperature measurements over a range of 30°C with an uncertainty below 1.4°C. The quality of the resulting temperature maps was independent of the distance from the metal, whereas the PRFS-based temperature measurements were increasingly impaired with increasing off-resonance.We demonstrated the ability to noninvasively measure temperature near metal using MSI and the T1 temperature sensitivity. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.26203

    View details for PubMedID 26991803

  • High temporal resolution dynamic MRI and arterial input function for assessment of GFR in pediatric subjects. Magnetic resonance in medicine Yoruk, U., Saranathan, M., Loening, A. M., Hargreaves, B. A., Vasanawala, S. S. 2016; 75 (3): 1301-1311

    Abstract

    To introduce a respiratory-gated high-spatiotemporal-resolution dynamic-contrast-enhanced MRI technique and a high-temporal-resolution aortic input function (HTR-AIF) estimation method for glomerular filtration rate (GFR) assessment in children.A high-spatiotemporal-resolution DCE-MRI method with view-shared reconstruction was modified to incorporate respiratory gating, and an AIF estimation method that uses a fraction of the k-space data from each respiratory period was developed (HTR-AIF). The method was validated using realistic digital phantom simulations and demonstrated on clinical subjects. The GFR estimates using HTR-AIF were compared with estimates obtained by using an AIF derived directly from the view-shared images.Digital phantom simulations showed that using the HTR-AIF technique gives more accurate AIF estimates (RMSE = 0.0932) compared with the existing estimation method (RMSE = 0.2059) that used view-sharing (VS). For simulated GFR > 27 mL/min, GFR estimation error was between 32% and 17% using view-shared AIF, whereas estimation error was less than 10% using HTR-AIF. In all clinical subjects, the HTR-AIF method resulted in higher GFR estimations than the view-shared method.The HTR-AIF method improves the accuracy of both the AIF and GFR estimates derived from the respiratory-gated acquisitions, and makes GFR estimation feasible in free-breathing pediatric subjects. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.25731

    View details for PubMedID 25946307

  • Volumetric multislice gagCEST imaging of articular cartilage: Optimization and comparison with T1rho. Magnetic resonance in medicine Kogan, F., Hargreaves, B. A., Gold, G. E. 2016

    Abstract

    To develop and optimize a multislice glycosaminoglycan (GAG) chemical exchange saturation transfer (GagCEST) sequence for volumetric imaging of articular cartilage, and to validate the sequence against T1ρ relaxation times in whole joint imaging of tibiotalar cartilage.Ex vivo experiments were used to observe the effect of the number of partitions and shot TR on signal-to-noise ratio and measured GagCESTasym . GagCEST imaging of the entire tibiotalar joint was also performed on 10 healthy subjects. The measured GagCESTasym was compared and correlated with T1ρ relaxation times.Ex vivo studies showed a higher average GagCESTasym from articular cartilage on multislice acquisitions acquired with two or more partitions than observed with a single-slice acquisition. In healthy human subjects, an average GagCESTasym of 8.8 ± 0.7% was observed. A coefficient of variation of GagCESTasym across slices of less than 15% was seen for all subjects. Across subjects, a Pearson correlation coefficient of -0.58 was observed between the measured gagCESTasym and T1ρ relaxation times.We demonstrated the feasibility and optimization of multislice GagCEST mapping of articular cartilage. Volumetric analysis and decreased scan times will help to advance the clinical utility of GagCEST imaging of articular cartilage. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.26200

    View details for PubMedID 26923108

  • High-resolution diffusion-weighted imaging of the breast with multiband 2D radiofrequency pulses and a generalized parallel imaging reconstruction. Magnetic resonance in medicine Taviani, V., Alley, M. T., Banerjee, S., Nishimura, D. G., Daniel, B. L., Vasanawala, S. S., Hargreaves, B. A. 2016

    Abstract

    To develop a technique for high-resolution diffusion-weighted imaging (DWI) and to compare it with standard DWI methods.Multiple in-plane bands of magnetization were simultaneously excited by identically phase modulating each subpulse of a two-dimensional (2D) RF pulse. Several excitations with the same multiband pattern progressively shifted in the phase-encode direction were used to cover the prescribed field of view (FOV). The phase-encoded FOV was limited to the width of a single band to reduce off-resonance-induced distortion and blurring. Parallel imaging (PI) techniques were used to resolve aliasing from the other bands and to combine the different excitations. Following validation in phantoms and healthy volunteers, a preliminary study in breast cancer patients (N=14) was performed to compare the proposed method to conventional DWI with PI and to reduced-FOV DWI.The proposed method gave high-resolution diffusion-weighted images with minimal artifacts at the band intersections. Compared to PI alone, higher phase-encoded FOV-reduction factors and reduced noise amplification were obtained, which translated to higher resolution images than conventional (non-multiband) DWI. The same resolution and image quality achievable over targeted regions using existing reduced-FOV methods was obtained, but the proposed method also enables complete bilateral coverage.We developed an in-plane multiband technique for high-resolution DWI and compared its performance with other standard DWI methods. Magn Reson Med 77:209-220, 2017. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.26110

    View details for PubMedID 26778549

  • Assessment of Tumor Morphology on Diffusion- Weighted (DWI) Breast MRI: Diagnostic Value of Reduced Field of View DWI JOURNAL OF MAGNETIC RESONANCE IMAGING Barentsz, M. W., Taviani, V., Chang, J. M., Ikeda, D. M., Miyake, K. K., Banerjee, S., Van den Bosch, M. A., Hargreaves, B. A., Daniel, B. L. 2015; 42 (6): 1656-1665

    Abstract

    To compare the diagnostic value of conventional, bilateral diffusion-weighted imaging (DWI) and high-resolution targeted DWI of known breast lesions.Twenty-one consecutive patients with known breast cancer or suspicious breast lesions were scanned with the conventional bilateral DWI technique, a high-resolution, reduced field of view (rFOV) DWI technique, and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) (3.0 T). We compared bilateral DWI and rFOV DWI quantitatively by measuring the lesions' apparent diffusion coefficient (ADC) values. For qualitative comparison, three dedicated breast radiologists scored image quality and performed lesion interpretation.In a phantom, ADC values were in good agreement with the reference values. Twenty-one patients (30 lesions: 14 invasive carcinomas, 10 benign lesions [of which 5 cysts], 3 high-risk, and 3 in situ carcinomas) were included. Cysts and high-risk lesions were excluded from the quantitative analysis. Quantitatively, both bilateral and rFOV DWI measured lower ADC values in invasive tumors than other lesions. In vivo, rFOV DWI gave lower ADC values than bilateral DWI (1.11 × 10(-3) mm(2) /s vs. 1.24 × 10(-3) mm(2) /s, P = 0.002). Regions of interest (ROIs) were comparable in size between the two techniques (2.90 vs. 2.13 cm(2) , P = 0.721). Qualitatively, all three radiologists scored sharpness of rFOV DWI images as significantly higher than bilateral DWI (P ≤ 0.002). Receiver operating characteristic (ROC) curve analysis showed a higher area under the curve (AUC) in BI-RADS classification for rFOV DWI compared to bilateral DWI (0.71 to 0.93 vs. 0.61 to 0.76, respectively).Tumor morphology can be assessed in more detail with high-resolution DWI (rFOV) than with standard bilateral DWI by providing significantly sharper images. J. MAGN. RESON. IMAGING 2015.

    View details for DOI 10.1002/jmri.24929

    View details for Web of Science ID 000368258100022

  • [18F]FDG PET/MRI of patients with chronic pain alters management: early experience. EJNMMI physics Biswal, S., Behera, D., Yoon, D. H., Holley, D., Ith, M. A., Carroll, I., Smuck, M., Hargreaves, B. 2015; 2: A84-?

    View details for DOI 10.1186/2197-7364-2-S1-A84

    View details for PubMedID 26956346

    View details for PubMedCentralID PMC4798651

  • Combined Outer Volume Suppression and T-2 Preparation Sequence for Coronary Angiography MAGNETIC RESONANCE IN MEDICINE Luo, J., Addy, N. O., Ingle, R. R., Hargreaves, B. A., Hu, B. S., Nishimura, D. G., Shin, T. 2015; 74 (6): 1632-1639

    Abstract

    To develop a magnetization preparation sequence for simultaneous outer volume suppression (OVS) and T2 weighting in whole-heart coronary magnetic resonance angiography.A combined OVS and T2 preparation sequence (OVS-T2 Prep) was designed with a nonselective adiabatic 90° tipdown pulse, two adiabatic 180° refocusing pulses, and a 2D spiral -90° tipup pulse. The OVS-T2 Prep preserves the magnetization inside an elliptic cylinder with T2 weighting, while saturating the magnetization outside the cylinder. Its performance was tested on phantoms and on 13 normal subjects with coronary magnetic resonance angiography using 3D cones trajectories.Phantom studies showed expected T2 -dependent signal amplitude in the spatial passband and suppressed signal in the spatial stopband. In vivo studies with full-field-of-view cones yielded a passband-to-stopband signal ratio of 3.18 ± 0.77 and blood-myocardium contrast-to-noise ratio enhancement by a factor of 1.43 ± 0.20 (P < 0.001). In vivo studies with reduced-field-of-view cones showed that OVS-T2 Prep well suppressed the aliasing artifacts, as supported by significantly reduced signal in the regions with no tissues compared to the images acquired without preparation (P < 0.0001).OVS-T2 Prep is a compact sequence that can accelerate coronary magnetic resonance angiography by suppressing signals from tissues surrounding the heart while simultaneously enhancing the blood-myocardium contrast.

    View details for DOI 10.1002/mrm.25575

    View details for Web of Science ID 000367737300014

    View details for PubMedCentralID PMC4470881

  • Balanced SSFP Dixon imaging with banding-artifact reduction at 3 Tesla MAGNETIC RESONANCE IN MEDICINE Quist, B., Hargreaves, B. A., Daniel, B. L., Saranathan, M. 2015; 74 (3): 706-715

    Abstract

    To develop a three-dimensional (3D) balanced steady-state free-precession (bSSFP) two-point Dixon method with banding-artifact suppression to offer robust high-resolution 3D bright-fluid imaging.A complex sum reconstruction that combines phase-cycled bSSFP images acquired at specific echo times for robust fat/water separation without banding was investigated and compared with a magnitude-based method. Bloch simulations using both single-peak and multiple-peak fat models were performed to predict the performance of these methods for a wide range of echo times and repetition times. The quality and degree of fat/water separation was evaluated in both simulations and using in vivo imaging.Simulations predicted that both effective banding-artifact suppression and substantial improvements in fat/water separation are possible at echo times that are different from conventional echo times, enabling improved spatial resolution. Comparisons between various echo times and repetition times in vivo validated the improved fat/water separation and effective banding-artifact removal predicted by the simulations.The proposed complex sum Dixon 3D bSSFP method is able to effectively separate fat and water at different sets of echo times, while removing banding-artifacts, providing a fast, high-resolution, T2 -like sequence without blurring. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.25449

    View details for Web of Science ID 000360222900012

  • Improved multislice perfusion imaging with velocity-selective arterial spin labeling. Journal of magnetic resonance imaging Zun, Z., Hargreaves, B. A., Rosenberg, J., Zaharchuk, G. 2015; 41 (5): 1422-1431

    Abstract

    To improve the multislice performance of velocity-selective arterial spin labeling (VS-ASL) imaging for cerebral blood flow (CBF) measurement such that it might be routinely applied for clinical applications with whole brain coverage.VS-ASL was performed with improvements such as timing optimization, stimulated echo removal, and slice profile sharpening. Each improvement was evaluated in volunteers by measuring temporal noise in the CBF measurement. VS-ASL with all these improvements was performed in 20 patients with Moyamoya disease some of whom also underwent xenon-enhanced CT (xeCT) imaging which was the reference standard for CBF measurement.Sequence timing optimization and inter-slice crosstalk reduction using stimulated echo removal and slice profile sharpening all contributed to reduction of temporal noise. VS-ASL imaging with all these improvements performed in Moyamoya disease patients showed significant reduction of temporal noise (P < 0.0001) and increased correlation coefficient with xeCT CBF imaging (from 0.07 to 0.62).We demonstrated that timing optimization, stimulated echo removal, and slice profile improvement have a large effect on image quality and robustness of VS-ASL in clinical imaging applications. J. Magn. Reson. Imaging 2015;41:1422-1431. © 2014 Wiley Periodicals, Inc.

    View details for DOI 10.1002/jmri.24652

    View details for PubMedID 24797337

  • AUTOMATED, NON-CONTRAST MRI FOR DETECTION OF SYNOVITIS USING DIFFUSION-WEIGHTED DESS Fan, A. P., Fong, G., Sveinsson, B., McWalter, E. J., Oei, E. H., Robinson, W. H., Genovese, M. C., Hargreaves, B. A., Gold, G. E. ELSEVIER SCI LTD. 2015: A240–A241

    View details for DOI 10.1016/j.joca.2015.02.447

    View details for Web of Science ID 000355048800404

  • MR Imaging Near Metallic Implants Using MAVRIC SL: Initial Clinical Experience at 3T ACADEMIC RADIOLOGY Gutierrez, L. B., Do, B. H., Gold, G. E., Hargreaves, B. A., Koch, K. M., Worters, P. W., Stevens, K. J. 2015; 22 (3): 370-379

    Abstract

    To compare the effectiveness of multiacquisition with variable resonance image combination selective (MAVRIC SL) with conventional two-dimensional fast spin-echo (2D-FSE) magnetic resonance (MR) techniques at 3T in imaging patients with a variety of metallic implants.Twenty-one 3T MR studies were obtained in 19 patients with different types of metal implants. Paired MAVRIC SL and 2D-FSE sequences were reviewed by two radiologists and compared for in-plane and through-plane metal artifact, visualization of the bone implant interface and surrounding soft tissues, blurring, and overall image quality using a two-tailed Wilcoxon signed rank test. The area of artifact on paired images was measured and compared using a paired Wilcoxon signed rank test. Changes in patient management resulting from MAVRIC SL imaging were documented.Significantly less in-plane and through-plane artifact was seen with MAVRIC SL, with improved visualization of the bone-implant interface and surrounding soft tissues, and superior overall image quality (P = .0001). Increased blurring was seen with MAVRIC SL (P = .0016). MAVRIC SL significantly decreased the image artifact compared to 2D-FSE (P = .0001). Inclusion of MAVRIC SL to the imaging protocol determined the need for surgery or type of surgery in five patients and ruled out the need for surgery in 13 patients. In three patients, the area of interest was well seen on both MAVRIC SL and 2D-FSE images, so the addition of MAVRIC had no effect on patient management.Imaging around metal implants with MAVRIC SL at 3T significantly improved image quality and decreased image artifact compared to conventional 2D-FSE imaging techniques and directly impacted patient management.

    View details for DOI 10.1016/j.acra.2014.09.010

    View details for Web of Science ID 000349659300014

    View details for PubMedID 25435186

  • Improved Frequency Selective Fat Suppression in the Posterior Neck With Tissue Susceptibility Matched Pyrolytic Graphite Foam JOURNAL OF MAGNETIC RESONANCE IMAGING Lee, G., Jordan, C., Tiet, P., Ruiz, C., McCormick, J., Phuong, K., Hargreaves, B., Conolly, S. 2015; 41 (3): 684-693

    Abstract

    To demonstrate improved frequency selective fat suppression in MRI using a magnetic susceptibility matching foam by reducing B0 inhomogeneities induced within the body by air-tissue interfaces.Flexible pyrolytic graphite (PG) composite foam was tailored to match the magnetic susceptibility of human tissue and was shaped to surround the cervical spine region. Field maps and frequency selective fat suppressed T1 -weighted FLASH images were acquired at 3 Tesla in both phantoms and six healthy necks.B0 field uniformity was shimmed to a target critical threshold of 1 ppm for fat suppression. The percentage of voxels in the phantom that did not achieve the critical threshold was reduced from 64% without the PG foam to only 1% with the foam. A similar decrease from 16% to 2% was observed in the in vivo region of interest.PG foam improved B0 field uniformity by moving air-tissue field gradients outside of the neck where they cannot cause MRI artifacts. The PG foams consistently mitigated signal dropout, improved overall SNR, and enabled more robust frequency selective fat suppression.

    View details for DOI 10.1002/jmri.24581

    View details for Web of Science ID 000349967700013

    View details for PubMedID 24677296

  • Hexagonal Undersampling for Faster MRI Near Metallic Implants MAGNETIC RESONANCE IN MEDICINE Sveinsson, B., Worters, P. W., Gold, G. E., Hargreaves, B. A. 2015; 73 (2): 662-668

    Abstract

    Slice encoding for metal artifact correction acquires a three-dimensional image of each excited slice with view-angle tilting to reduce slice and readout direction artifacts respectively, but requires additional imaging time. The purpose of this study was to provide a technique for faster imaging around metallic implants by undersampling k-space.Assuming that areas of slice distortion are localized, hexagonal sampling can reduce imaging time by 50% compared with conventional scans. This work demonstrates this technique by comparisons of fully sampled images with undersampled images, either from simulations from fully acquired data or from data actually undersampled during acquisition, in patients and phantoms. Hexagonal sampling is also shown to be compatible with parallel imaging and partial Fourier acquisitions. Image quality was evaluated using a structural similarity (SSIM) index.Images acquired with hexagonal undersampling had no visible difference in artifact suppression from fully sampled images. The SSIM index indicated high similarity to fully sampled images in all cases.The study demonstrates the ability to reduce scan time by undersampling without compromising image quality. Magn Reson Med 73:662-668, 2015. © 2014 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.25132

    View details for Web of Science ID 000348139500023

    View details for PubMedID 24549782

    View details for PubMedCentralID PMC4156560

  • Metal Artifact Reduction With MAVRIC SL at 3-T MRI in Patients With Hip Arthroplasty AMERICAN JOURNAL OF ROENTGENOLOGY Choi, S., Koch, K. M., Hargreaves, B. A., Stevens, K. J., Gold, G. E. 2015; 204 (1): 140-147

    Abstract

    The objective of our study was to compare the multiacquisition variable-resonance image combination selective (MAVRIC SL) sequence with the 2D fast spin-echo (FSE) sequence for metal artifact reduction on 3-T MRI in patients with hip arthroplasty (HA).Matched 2D FSE and MAVRIC SL images of 21 hips (19 patients with HA) were included in the study group. Paired image sets, composed of 13 coronal and 12 axial slices (total, 25 image sets), of the 21 hips were evaluated. For quantitative analysis, the artifact area was measured at the level of the hip and femur. For qualitative analysis, two musculoskeletal radiologists independently compared paired 2D FSE and MAVRIC SL sets in terms of artifacts, depiction of anatomic detail, level of diagnostic confidence, and detection of abnormal findings.The measured artifact area was significantly smaller (p < 0.05) on MAVRIC SL than 2D FSE at both the level of hip (59.9% reduction with MAVRIC SL) and femur (31.3% reduction with MAVRIC SL). The artifact score was also significantly decreased (p < 0.0001) with MAVRIC SL compared with 2D FSE for both reviewers. The hip joint capsule and the muscle and tendon attachment sites of the obturator externus and iliopsoas muscles were better depicted with MAVRIC SL than 2D FSE (p < 0.0125). Abnormal findings were significantly better shown on MAVRIC SL imaging compared with 2D FSE imaging (p < 0.0001).The MAVRIC SL sequence can significantly reduce metal artifact on 3-T MRI compared with the 2D FSE sequence and can increase diagnostic confidence of 3-T MRI in patients with total HA.

    View details for DOI 10.2214/AJR.13.11785

    View details for Web of Science ID 000348562300044

    View details for PubMedID 25539249

    View details for PubMedCentralID PMC4321802

  • High resolution multi-arterial phase MRI improves lesion contrast in chronic liver disease. Clinical and investigative medicine. Médecine clinique et experimentale Clarke, S. E., Saranathan, M., Rettmann, D. W., Hargreaves, B. A., Vasanawala, S. S. 2015; 38 (3): E90-9

    View details for PubMedID 26026643

  • High resolution multi-arterial phase MRI improves lesion contrast in chronic liver disease. Clinical and investigative medicine. Me´decine clinique et experimentale Clarke, S. E., Saranathan, M., Rettmann, D. W., Hargreaves, B. A., Vasanawala, S. S. 2015; 38 (3): E90-9

    Abstract

    To determine the reliability of arterial phase capture and evaluate hypervascular lesion contrast kinetics with a combined view-sharing and parallel imaging dynamic contrast-enhanced acquisition, DIfferential Sub-sampling with Cartesian Ordering (DISCO), in patients with known chronic liver disease.A retrospective review of 3T MR images from 26 patients with known chronic liver disease referred for hepatocellular carcinoma surveillance or post-treatment follow up was performed. After administration of a gadolinium-based contrast agent, a multiphasic acquisition was obtained in a 28 s breath-hold, from which seven sequential post-contrast image volumes were reconstructed.The late arterial phase was successfully captured in all cases (26/26, 95% CI 87-100%). Images obtained 26 s post-injection had the highest frequency of late arterial phase capture (20/26) and lesion detection (23/26) of any individual post-contrast time; however, the multiphasic data resulted in a significantly higher frequency of late arterial phase capture (26/26, p=0.03) and a higher relative contrast (5.37+/-0.97 versus 7.10+/-0.98, p < 0.01).Multiphasic acquisition with combined view-sharing and parallel imaging reliably captures the late arterial phase and provides sufficient temporal resolution to characterize hepatic lesion contrast kinetics in patients with chronic liver disease while maintaining high spatial resolution.

    View details for PubMedID 26026643

  • Variable Spatiotemporal Resolution Three-Dimensional Dixon Sequence for Rapid Dynamic Contrast-Enhanced Breast MRI JOURNAL OF MAGNETIC RESONANCE IMAGING Saranathan, M., Rettmann, D. W., Hargreaves, B. A., Lipson, J. A., Daniel, B. L. 2014; 40 (6): 1392-?

    Abstract

    To investigate a new variable spatiotemporal resolution dynamic contrast-enhanced (DCE) MRI method termed DIfferential Subsampling with Cartesian Ordering (DISCO), for imaging of breast cancer.DISCO combines variable density, pseudorandom k-space segmentation and two-point Dixon fat-water separation for high spatiotemporal resolution breast DCE MRI. During the contrast wash-in phase, view sharing is used to achieve high temporal resolution. Forty patients referred for breast MRI were imaged, 26 using the proposed DISCO sequence and 14 using a conventional low-spatial-resolution dynamic sequence (VIBRANT-FLEX) on a 3 Tesla scanner. DISCO dynamic images from 14 patients were compared with VIBRANT-FLEX images from 14 other patients. The image quality assessed by radiologist image ranking in a blinded manner, and the temporal characteristics of the two sequences were compared.A spatial resolution of 1.1 × 1.1 × 1.2 mm(3) (160 slices, 28 cm field of view) was achieved with axial bilateral coverage in 120 s. Dynamic images with ∼ 9 s effective temporal resolution were generated during the 2-min contrast wash-in phase. The image quality of DISCO dynamic images ranked significantly higher than low spatial resolution VIBRANT-FLEX images (19.5 versus 9.5, Mann-Whitney U-test P = 0.00914), with no significant differences in the maximum slope of aortic enhancement.DISCO is a promising variable-spatiotemporal-resolution imaging sequence for capturing the dynamics of rapidly enhancing tumors as well as structural features postcontrast. A near 1-mm isotropic spatial resolution was achieved with postcontrast static phase images in 120 s and dynamic phase images acquired in 9 s per phase.

    View details for DOI 10.1002/jmri.24490

    View details for Web of Science ID 000344786200001

    View details for PubMedCentralID PMC4019731

  • Variability of CubeQuant T-1 rho, quantitative DESS T-2, and cones sodium MRI in knee cartilage OSTEOARTHRITIS AND CARTILAGE Jordan, C. D., McWalter, E. J., Monu, U. D., Watkins, R. D., Chen, W., Bangerter, N. K., Hargreaves, B. A., Gold, G. E. 2014; 22 (10): 1559-1567

    Abstract

    To measure the variability of T1ρ relaxation times using CubeQuant, T2 relaxation times using quantitative double echo in steady state (DESS), and normalized sodium signals using 3D cones sodium magnetic resonance imaging (MRI) of knee cartilage in vivo at 3 T.Eight healthy subjects were scanned at 3 T at baseline, 1 day, 5 months, and 1 year. Ten regions of interest (ROIs) of knee cartilage were segmented in the medial and lateral compartments of each subject's knee. T1ρ and T2 relaxation times and normalized sodium signals were measured and the root-mean-square coefficient of variation (CVRMS) was calculated. Intra-subject variability was measured over short, moderate and long-term, as well as intra-observer and inter-observer variability.The average intra-subject CVRMS measurements over short, moderate, and long-term time periods were 4.6%, 6.1%, and 6.0% for the T1ρ measurements, 6.4%, 9.3%, and 10.7% for the T2 measurements and 11.3%, 11.6%, and 12.9% for the sodium measurements, respectively. The average CVRMS measurements for intra-observer and inter-observer segmentation were 3.8% and 5.7% for the T1ρ measurements, 4.7% and 6.7% for the T2 measurements, and 8.1% and 11.4% for the sodium measurements, respectively.These CVRMS measurements are substantially lower than previously measured changes expected in patients with advanced osteoarthritis compared to healthy volunteers, suggesting that CubeQuant T1ρ, quantitative DESS T2 and 3D cones sodium measurements are sufficiently sensitive for in vivo cartilage studies.

    View details for DOI 10.1016/j.joca.2014.06.001

    View details for Web of Science ID 000343139800027

    View details for PubMedCentralID PMC4185151

  • Near-contiguous spin echo imaging using matched-phase RF and its application in velocity-selective arterial spin labeling. Magnetic resonance in medicine Zun, Z., Hargreaves, B. A., Pauly, J., Zaharchuk, G. 2014; 71 (6): 2043-2050

    Abstract

    The minimum slice spacing in multislice imaging is limited by inter-slice crosstalk due to an imperfect slice profile. This study sought to minimize the slice spacing using matched-phase RF pulses and demonstrate its application in cerebral blood flow imaging using velocity-selective arterial spin labeling.A spin-echo matched-phase 90°-180° RF pair was designed using Shinnar-Le Roux algorithm in order to improve the slice profile of longitudinal magnetization, which plays a more critical role in creating interslice crosstalk than transverse magnetization. Both transverse and longitudinal slice profiles were compared between matched-phase RF and sinc-based RF pulses in simulations and measurements. Velocity-selective arterial spin labeling was performed in normal volunteers using both RF pulses and standard deviation of cerebral blood flow time series was calculated to examine ASL signal stability.Using designed matched-phase RF, the longitudinal slice profile was sharpened without signal-to-noise ratio loss. In velocity-selective arterial spin labeling imaging, the temporal standard deviation of cerebral blood flow measurements was reduced from 48 mL/100 g/min to 32 mL/100 g/min by 33% using matched-phase RF pulses, and as a result, cerebral blood flow image quality improved.This study reports that near-contiguous multislice imaging can be achieved using matched-phase RF pulses without compromising signal-to-noise ratio and signal stability. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.24866

    View details for PubMedID 23857667

  • Optimizing isotropic three-dimensional fast spin-echo methods for imaging the knee. Journal of magnetic resonance imaging Li, C. Q., Chen, W., Rosenberg, J. K., Beatty, P. J., Kijowski, R., Hargreaves, B. A., Busse, R. F., Gold, G. E. 2014; 39 (6): 1417-1425

    Abstract

    To optimize acquisition parameters for three dimensional fast spin-echo (3D FSE) imaging of the knee.The knees of eight healthy volunteers were imaged in a 3 Tesla MRI scanner using an eight-channel knee coil. A total of 146 intermediate weighted isotropic resolution 3D FSE (3D-FSE-Cube)images with varied acquisition parameter settings were acquired with an additional reference scan performed for subjective image quality assessment. Images were graded for overall quality, parallel imaging artifact severity and blurring. Cartilage, muscle, and fluid signal-to-noise ratios and fluid-cartilage contrast-to-noise ratios were quantified by acquiring scans without radio frequency excitation and custom-reconstructing the k-space data.Mixed effects regression modeling was used to determine statistically significant effects of different parameters on image quality.Changes in receiver bandwidth, repetition time and echo train length significantly affected all measurements of image quality (P < 0.05). Reducing band width improved all metrics of image quality with the exception of blurring. Reader agreement was slight to fair for subjective metrics, but overall trends in quality ratings were apparent.We used a systematic approach to optimize 3D-FSE-Cube parameters for knee imaging. Image quality was overall improved using a receiver bandwidth of 631.25 kHz, and blurring increased with lower band width and longer echo trains.

    View details for PubMedID 24987753

  • Imaging Near Metal: The Impact of Extreme Static Local Field Gradients on Frequency Encoding Processes MAGNETIC RESONANCE IN MEDICINE Koch, K. M., King, K. F., Carl, M., Hargreaves, B. A. 2014; 71 (6): 2024-2034

    Abstract

    Magnetic resonance imaging capabilities in the direct vicinity of metallic devices have substantially improved with the recent development of three-dimensional multispectral imaging (3D-MSI) methods. When imaging near metallic hardware, the bulk image distortions in 3D-MSI techniques are reduced to the single-pixel level. However, commonly utilized MSI techniques are ultimately limited by frequency-encoding processes and reveal a class of residual intensity-based susceptibility artifacts that have yet to be formally analyzed.Empirical measurements and simulation techniques are utilized to study the static local magnetic field gradients induced by metal implants and their general impact on frequency-encoding processes. The specific consequences of these gradients on 3D-MSI approaches are also analyzed using empirical and simulated approaches.Close agreements between empirical and simulated measurements clearly demonstrate the effects of strong local gradients on frequency-encoded imaging capabilities near metallic implants.3D-MSI techniques can enable substantially enhanced magnetic resonance imaging capabilities near metallic implants. However, strong local static field gradients generate residual artifacts whose direct mitigation are ultimately limited by frequency encoding processes. Applications of 3D encoding strategies or additional post processing may be required to further reduce residual artifacts in multispectral images near metal implants.

    View details for DOI 10.1002/mrm.24862

    View details for Web of Science ID 000336260900010

    View details for PubMedID 23843341

  • Mechanisms of osteoarthritis in the knee: MR imaging appearance. Journal of magnetic resonance imaging Shapiro, L. M., McWalter, E. J., Son, M., Levenston, M., Hargreaves, B. A., Gold, G. E. 2014; 39 (6): 1346-1356

    Abstract

    Osteoarthritis has grown to become a widely prevalent disease that has major implications in both individual and public health. Although originally considered to be a degenerative disease driven by "wear and tear" of the articular cartilage, recent evidence has led to a consensus that osteoarthritis pathophysiology should be perceived in the context of the entire joint and multiple tissues. MRI is becoming an increasingly more important modality for imaging osteoarthritis, due to its excellent soft tissue contrast and ability to acquire morphological and biochemical data. This review will describe the pathophysiology of osteoarthritis as it is associated with various tissue types, highlight several promising MR imaging techniques for osteoarthritis and illustrate the expected appearance of osteoarthritis with each technique.

    View details for DOI 10.1002/jmri.24562

    View details for PubMedID 24677706

    View details for PubMedCentralID PMC4016127

  • Optimizing Isotropic Three-Dimensional Fast Spin-Echo Methods for Imaging the Knee JOURNAL OF MAGNETIC RESONANCE IMAGING Li, C. Q., Chen, W., Rosenberg, J. K., Beatty, P. J., Kijowski, R., Hargreaves, B. A., Busse, R. F., Gold, G. E. 2014; 39 (6): 1417-1425

    Abstract

    To optimize acquisition parameters for three dimensional fast spin-echo (3D FSE) imaging of the knee.The knees of eight healthy volunteers were imaged in a 3 Tesla MRI scanner using an eight-channel knee coil. A total of 146 intermediate weighted isotropic resolution 3D FSE (3D-FSE-Cube)images with varied acquisition parameter settings were acquired with an additional reference scan performed for subjective image quality assessment. Images were graded for overall quality, parallel imaging artifact severity and blurring. Cartilage, muscle, and fluid signal-to-noise ratios and fluid-cartilage contrast-to-noise ratios were quantified by acquiring scans without radio frequency excitation and custom-reconstructing the k-space data.Mixed effects regression modeling was used to determine statistically significant effects of different parameters on image quality.Changes in receiver bandwidth, repetition time and echo train length significantly affected all measurements of image quality (P < 0.05). Reducing band width improved all metrics of image quality with the exception of blurring. Reader agreement was slight to fair for subjective metrics, but overall trends in quality ratings were apparent.We used a systematic approach to optimize 3D-FSE-Cube parameters for knee imaging. Image quality was overall improved using a receiver bandwidth of 631.25 kHz, and blurring increased with lower band width and longer echo trains.

    View details for DOI 10.1002/jmri.24315

    View details for Web of Science ID 000335460500010

    View details for PubMedCentralID PMC4083613

  • High-resolution, three-dimensional diffusion-weighted breast imaging using DESS. Magnetic resonance imaging Granlund, K. L., Staroswiecki, E., Alley, M. T., Daniel, B. L., Hargreaves, B. A. 2014; 32 (4): 330-341

    Abstract

    To evaluate the use of the double-echo steady-state (DESS) sequence for acquiring high-resolution breast images with diffusion and T2 weighting.Phantom scans were used to verify the T2 and diffusion weighting of the DESS sequence. Image distortion was evaluated in volunteers by comparing DESS images and conventional diffusion-weighted images (DWI) to spoiled gradient-echo images. The DESS sequence was added to a standard clinical protocol, and the resulting patient images were used to evaluate overall image quality and image contrast in lesions.The diffusion weighting of the DESS sequence can be easily modulated by changing the spoiler gradient area and flip angle. Radiologists rated DESS images as having higher resolution and less distortion than conventional DWI. Lesion-to-tissue contrast ratios are strongly correlated between DWI and DESS images (R=0.83) and between T2-weighted fast spin-echo and DESS images (R=0.80).The DESS sequence is able to acquire high-resolution 3D diffusion- and T2-weighted images in short scan times, with image quality that facilitates morphological assessment of lesions.

    View details for DOI 10.1016/j.mri.2013.12.014

    View details for PubMedID 24512800

  • Homogenous Fat Suppression for Bilateral Breast Imaging Using Independent Shims MAGNETIC RESONANCE IN MEDICINE Han, M., Cunningham, C. H., Pauly, J. M., Daniel, B. L., Hargreaves, B. A. 2014; 71 (4): 1511-1517

    Abstract

    To demonstrate the capability of incorporating independent shims into a dual-band spectral-spatial excitation and to compare fat suppression between standard global shims and independent shims for in vivo bilateral breast imaging at 1.5T.A dual-band spectral-spatial excitation pulse was designed by interleaving two flyback spectral-spatial pulses, playing one during positive gradient lobes and the other during negative gradient lobes. Each slab was enabled to have an independent spatial offset, spectral offset, and slab-phase modulation by modulating radiofrequency phase, and independent linear shims were incorporated by playing extra shim gradients. Phantom experiments were performed to demonstrate the functionality of the pulse, and in vivo experiments were performed for 10 healthy volunteers to compare fat suppression between standard shims and independent shims.The phantom experiments confirmed that the dual-band pulse can provide independent spectral and spatial offsets and linear shims to the two slabs. Independent shims provided qualitatively more homogeneous fat suppression than standard shims in seven out of 10 subjects, with equivalent fat suppression in two of the other three subjects.Incorporating independent shims into the dual-band spectral-spatial excitation can provide homogeneous fat suppression in bilateral breast imaging.

    View details for DOI 10.1002/mrm.24803

    View details for Web of Science ID 000333040500017

    View details for PubMedID 23821305

    View details for PubMedCentralID PMC4085331

  • NON-CONTRAST DIFFUSION WEIGHTED IMAGING FOR THE ASSESSMENT OF KNEE SYNOVITIS: A COMPARATIVE STUDY AGAINST CONTRAST-ENHANCED MRI Oei, E. H., McWalter, E. J., Sveinsson, B., Alley, M. T., Hargreaves, B. A., Gold, G. E. ELSEVIER SCI LTD. 2014: S252

    View details for DOI 10.1016/j.joca.2014.02.481

    View details for Web of Science ID 000335424800465

  • 3D T2-Weighted Spin Echo Imaging in the Breast JOURNAL OF MAGNETIC RESONANCE IMAGING Moran, C. J., Hargreaves, B. A., Saranathan, M., Lipson, J. A., Kao, J., Ikeda, D. M., Daniel, B. L. 2014; 39 (2): 332-338

    Abstract

    PURPOSE: To evaluate the performance of 2D versus 3D T2-weighted spin echo imaging in the breast. MATERIALS AND METHODS: 2D and 3D T2-weighted images were acquired in 25 patients as part of a clinically indicated breast magnetic resonance imaging (MRI) exam. Lesion-to-fibroglandular tissue signal ratio was measured in 16 identified lesions. Clarity of lesion morphology was assessed through a blinded review by three radiologists. Instances demonstrating the potential diagnostic contribution of 3D versus 2D T2-weighted imaging in the breast were noted through unblinded review by a fourth radiologist. RESULTS: The lesion-to-fibroglandular tissue signal ratio was well correlated between 2D and 3D T2-weighted images (R(2)  = 0.93). Clarity of lesion morphology was significantly better with 3D T2-weighted imaging for all observers based on a McNemar test (P ≤ 0.02, P ≤ 0.01, P ≤ 0.03). Instances indicating the potential diagnostic contribution of 3D T2-weighted imaging included improved depiction of signal intensity and improved alignment between DCE and T2-weighted findings. CONCLUSION: In this pilot study, 3D T2-weighted imaging provided comparable contrast and improved depiction of lesion morphology in the breast in comparison to 2D T2-weighted imaging. Based on these results further investigation to determine the diagnostic impact of 3D T2-weighted imaging in breast MRI is warranted.J. Magn. Reson. Imaging 2013;00:000-000. © 2013 Wiley Periodicals, Inc.

    View details for DOI 10.1002/jmri.24151

    View details for Web of Science ID 000329753400011

    View details for PubMedID 23596017

  • The John Charnley Award: Diagnostic Accuracy of MRI Versus Ultrasound for Detecting Pseudotumors in Asymptomatic Metal-on-Metal THA Open Scientific Meeting of the Hip-Society in Conjunction with the Annual Meeting of the American-Academy-of-Orthopaedic-Surgeons (AAOS) Garbuz, D. S., Hargreaves, B. A., Duncan, C. P., Masri, B. A., Wilson, D. R., Forster, B. B. SPRINGER. 2014: 417–23

    Abstract

    The prevalence of pseudotumors in patients with large-head metal-on-metal (MOM) THA has been the subject of implant recalls and warnings from various regulatory agencies. To date, there is no consensus on whether ultrasound or MRI is superior for the detection of pseudotumors.We prospectively compared ultrasound to MRI for pseudotumor detection in an asymptomatic cohort of patients with MOM THAs. We also compared ultrasound to MRI for assessment of pseudotumor growth and progressive soft tissue involvement at a 6-month interval.We enrolled 40 patients with large-head MOM THAs in the study. The mean age was 54 years (range, 34-76 years). The mean time from surgery was 54 months (range, 40-81 months). There were 28 men and 12 women. All patients underwent ultrasound and MRI using slice encoding for metal artifact correction. The gold standard was defined as follows: if both ultrasound and MRI agreed, this was interpreted as concordant and the result was considered accurate.Ultrasound and MRI agreed in 37 of 40 patients (93%). The prevalence of pseudotumors was 31% (12 of 39) in our cohort. Twenty-three of 39 patients (59%) had completely normal tests and four (10%) had simple fluid collections. Ultrasound had a sensitivity of 100% and specificity of 96% while MRI had a sensitivity of 92% and specificity of 100%.A negative ultrasound rules out pseudotumor in asymptomatic patients as this test is 100% sensitive. Given its lower cost, we recommend ultrasound as the initial screening tool for pseudotumors.

    View details for DOI 10.1007/s11999-013-3181-6

    View details for Web of Science ID 000330585000007

    View details for PubMedID 23868425

    View details for PubMedCentralID PMC3890209

  • High-Frequency Subband Compressed Sensing MRI Using Quadruplet Sampling MAGNETIC RESONANCE IN MEDICINE Sung, K., Hargreaves, B. A. 2013; 70 (5): 1306-1318

    Abstract

    PURPOSE: To present and validate a new method that formalizes a direct link between k-space and wavelet domains to apply separate undersampling and reconstruction for high- and low-spatial-frequency k-space data. THEORY AND METHODS: High- and low-spatial-frequency regions are defined in k-space based on the separation of wavelet subbands, and the conventional compressed sensing problem is transformed into one of localized k-space estimation. To better exploit wavelet-domain sparsity, compressed sensing can be used for high-spatial-frequency regions, whereas parallel imaging can be used for low-spatial-frequency regions. Fourier undersampling is also customized to better accommodate each reconstruction method: random undersampling for compressed sensing and regular undersampling for parallel imaging. RESULTS: Examples using the proposed method demonstrate successful reconstruction of both low-spatial-frequency content and fine structures in high-resolution three-dimensional breast imaging with a net acceleration of 11-12. CONCLUSION: The proposed method improves the reconstruction accuracy of high-spatial-frequency signal content and avoids incoherent artifacts in low-spatial-frequency regions. This new formulation also reduces the reconstruction time due to the smaller problem size. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.24592

    View details for Web of Science ID 000326115000013

    View details for PubMedID 23280540

  • Improvement of gadoxetate arterial phase capture with a high spatio-temporal resolution multiphase three-dimensional SPGR-dixon sequence. Journal of magnetic resonance imaging Hope, T. A., Saranathan, M., Petkovska, I., Hargreaves, B. A., Herfkens, R. J., Vasanawala, S. S. 2013; 38 (4): 938-945

    Abstract

    PURPOSE: To determine whether a multiphase method with high spatiotemporal resolution (STR) by means of a combination of parallel imaging, pseudorandom sampling and temporal view sharing improves the capture and intensity of gadoxetate arterial phase images as well as lesion enhancement. MATERIALS AND METHODS: Thirty-seven patients were imaged with a conventional spoiled gradient echo acquisition and 48 with a high STR multiphase acquisition after the administration of gadoxetate. Arterial phase capture, image quality, and quality of fat suppression were qualitatively graded. Fourteen lesions in the conventional group and 28 in the high STR multiphase group were imaged, including 34 focal nodular hyperplasias. The ratio of lesion to parenchyma enhancement as well as relative hepatic artery enhancement were calculated. Chi-squared, Mann-Whitney U and student t-tests were used to compare differences. RESULTS: The high STR multiphase acquisition included the arterial phase more frequently than conventional acquisitions (P < 0.001), with the arterial phase missed in 17% (95% CI of 4-28%) of patients with conventional acquisition compared with 2% (95% CI of 0-6%) with the high STR multiphase acquisition. There was no loss of image quality or degree of fat saturation. Additionally, there was increased relative intensity of the hepatic arteries (P < 0.001) as well as lesion enhancement (P = 0.01). CONCLUSION: The high STR multiphase acquisition resulted in more reliable gadoxetate arterial phase capture compared with a conventional acquisition while preserving image quality with robust fat saturation J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.

    View details for DOI 10.1002/jmri.24048

    View details for PubMedID 23371926

  • Simultaneous T-1 and B-1(+) Mapping Using Reference Region Variable Flip Angle Imaging MAGNETIC RESONANCE IN MEDICINE Sung, K., Saranathan, M., Daniel, B. L., Hargreaves, B. A. 2013; 70 (4): 954-961

    Abstract

    To present a new method that can simultaneously and efficiently measure T1 and B1 (+) maps using reference region variable flip angle (RR-VFA) imaging.Assuming T1 relaxation time in a reference region such as fat is well characterized, and the reference region sufficiently covers smoothly varying B1 (+) field inhomogeneity, B1 (+) maps can be measured from VFA images, conventionally used for T1 measurements. Fat-only images from two-point Dixon acquisitions were used to compute B1 (+) maps, and the B1 (+) maps were compared with ones using the double-angle method (DAM) in 22 breast MRI patients at 3T. Additionally, high spatial resolution VFA images were acquired to show T1 measurements with and without the RR-VFA B1 (+) correction in six patients.RR-VFA is able to generate reliable B1 (+) maps, similar to those using the conventional DAM. This simultaneous T1 and B1 (+) mapping can also be used to reduce T1 estimation errors, where T1 maps have more uniform fibroglandular tissue T1 and better depiction of heterogeneous T1 of breast masses.A new method that can measure both T1 and B1 (+) maps based on Dixon VFA images is described, offering improved T1 quantification with no scan time penalty.

    View details for DOI 10.1002/mrm.24904

    View details for Web of Science ID 000325136300007

    View details for PubMedCentralID PMC3923865

  • Location constrained approximate message passing for compressed sensing MRI MAGNETIC RESONANCE IN MEDICINE Sung, K., Daniel, B. L., Hargreaves, B. A. 2013; 70 (2): 370-381

    Abstract

    Iterative thresholding methods have been extensively studied as faster alternatives to convex optimization methods for solving large-sized problems in compressed sensing. A novel iterative thresholding method called LCAMP (Location Constrained Approximate Message Passing) is presented for reducing computational complexity and improving reconstruction accuracy when a nonzero location (or sparse support) constraint can be obtained from view shared images. LCAMP modifies the existing approximate message passing algorithm by replacing the thresholding stage with a location constraint, which avoids adjusting regularization parameters or thresholding levels. This work is first compared with other conventional reconstruction methods using random one-dimention signals and then applied to dynamic contrast-enhanced breast magnetic resonance imaging to demonstrate the excellent reconstruction accuracy (less than 2% absolute difference) and low computation time (5-10 s using Matlab) with highly undersampled three-dimentional data (244 × 128 × 48; overall reduction factor = 10). Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.

    View details for DOI 10.1002/mrm.24468

    View details for Web of Science ID 000322128300010

    View details for PubMedID 23042658

  • Transmit B-1(+) Field Inhomogeneity and T-1 Estimation Errors in Breast DCE-MRI at 3 Tesla JOURNAL OF MAGNETIC RESONANCE IMAGING Sung, K., Daniel, B. L., Hargreaves, B. A. 2013; 38 (2): 454-459

    Abstract

    PURPOSE: To quantify B 1+ variation across the breasts and to evaluate the accuracy of precontrast T(1) estimation with and without B 1+ variation in breast MRI patients at 3 Tesla (T). MATERIALS AND METHODS: B 1+ and variable flip angle (VFA) T(1) mapping were included in our dynamic contrast-enhanced (DCE) breast imaging protocol to study a total of 25 patients on a 3.0T GE MR 750 system. We computed precontrast T(1) relaxation in fat, which we assumed to be consistent across a cohort of breast imaging subjects, with and without compensation for B 1+ variation. The mean and standard deviation of B 1+ and T(1) values were calculated for statistical data analysis. RESULTS: Our measurements showed a consistent B 1+ field difference between the left and right breasts. The left breast has an average 15.4% higher flip angle than the prescribed flip angle, and the right breast has an average 17.6% lower flip angle than the prescribed flip angle. This average 33% flip angle difference, which can be vendor and model specific, creates a 52% T(1) estimation bias in fat between breasts using the VFA T(1) mapping technique. The T(1) variation is reduced to 7% by including B 1+ correction. CONCLUSION: We have shown that severe B 1+ variation over the breasts can cause a substantial error in T(1) estimation between the breasts, in VFA T(1) maps at 3T, but that compensating for these variations can considerably improve accuracy of T(1) measurements, which can directly benefit quantitative breast DCE-MRI at 3T. J. Magn. Reson. Imaging 2012;. © 2012 Wiley Periodicals, Inc.

    View details for DOI 10.1002/jmri.23996

    View details for Web of Science ID 000323205300024

    View details for PubMedID 23292822

    View details for PubMedCentralID PMC3620726

  • Regional variation in T1? and T2 times in osteoarthritic human menisci: correlation with mechanical properties and matrix composition. Osteoarthritis and cartilage Son, M., Goodman, S. B., Chen, W., Hargreaves, B. A., Gold, G. E., Levenston, M. E. 2013; 21 (6): 796-805

    Abstract

    Changes in T1ρ and T2 magnetic resonance relaxation times have been associated with articular cartilage degeneration, but similar relationships for meniscal tissue have not been extensively investigated. This work examined relationships between T1ρ and T2 measurements and biochemical and mechanical properties across regions of degenerate human menisci.Average T1ρ and T2 relaxation times were determined for nine regions each of seven medial and 13 lateral menisci from 14 total knee replacement patients. Sulfated glycosaminoglycan (sGAG), collagen and water contents were measured for each region. Biomechanical measurements of equilibrium compressive, dynamic compressive and dynamic shear moduli were made for anterior, central and posterior regions.T1ρ and T2 times showed similar regional patterns, with longer relaxation times in the (radially) middle region compared to the inner and outer regions. Pooled over all regions, T1ρ and T2 times showed strong correlations both with one another and with water content. Correlations with biochemical content varied depending on normalization to wet or dry mass, and both imaging parameters showed stronger correlations with collagen compared to sGAG content. Mechanical properties displayed moderate inverse correlations with increasing T1ρ and T2 times and water content.Both T1ρ and T2 relaxation times correlated strongly with water content and moderately with mechanical properties in osteoarthritic menisci, but not as strongly with sGAG or collagen contents alone. While the ability of magnetic resonance imaging (MRI) to detect early osteoarthritic changes remains the subject of investigation, these results suggest that T1ρ and T2 relaxation times have limited ability to detect compositional variations in degenerate menisci.

    View details for DOI 10.1016/j.joca.2013.03.002

    View details for PubMedID 23499673

  • Musculoskeletal MRI at 3.0 T and 7.0 T: A comparison of relaxation times and image contrast EUROPEAN JOURNAL OF RADIOLOGY Jordan, C. D., Saranathan, M., Bangerter, N. K., Hargreaves, B. A., Gold, G. E. 2013; 82 (5): 734-739

    Abstract

    The purpose of this study was to measure and compare the relaxation times of musculoskeletal tissues at 3.0 T and 7.0 T, and to use these measurements to select appropriate parameters for musculoskeletal protocols at 7.0 T.We measured the T₁ and T₂ relaxation times of cartilage, muscle, synovial fluid, bone marrow and subcutaneous fat at both 3.0 T and 7.0 T in the knees of five healthy volunteers. The T₁ relaxation times were measured using a spin-echo inversion recovery sequence with six inversion times. The T₂ relaxation times were measured using a spin-echo sequence with seven echo times. The accuracy of both the T₁ and T₂ measurement techniques was verified in phantoms at both magnetic field strengths. We used the measured relaxation times to help design 7.0 T musculoskeletal protocols that preserve the favorable contrast characteristics of our 3.0 T protocols, while achieving significantly higher resolution at higher SNR efficiency.The T₁ relaxation times in all tissues at 7.0 T were consistently higher than those measured at 3.0 T, while the T₂ relaxation times at 7.0 T were consistently lower than those measured at 3.0 T. The measured relaxation times were used to help develop high resolution 7.0 T protocols that had similar fluid-to-cartilage contrast to that of the standard clinical 3.0 T protocols for the following sequences: proton-density-weighted fast spin-echo (FSE), T₂-weighted FSE, and 3D-FSE-Cube.The T₁ and T₂ changes were within the expected ranges. Parameters for musculoskeletal protocols at 7.0 T can be optimized based on these values, yielding improved resolution in musculoskeletal imaging with similar contrast to that of standard 3.0 T clinical protocols.

    View details for DOI 10.1016/j.ejrad.2011.09.021

    View details for Web of Science ID 000317335800012

    View details for PubMedID 22172536

    View details for PubMedCentralID PMC3310288

  • Application of advanced magnetic resonance imaging techniques in evaluation of the lower extremity. Radiologic clinics of North America Braun, H. J., Dragoo, J. L., Hargreaves, B. A., Levenston, M. E., Gold, G. E. 2013; 51 (3): 529-545

    View details for DOI 10.1016/j.rcl.2012.12.001

    View details for PubMedID 23622097

  • Application of advanced magnetic resonance imaging techniques in evaluation of the lower extremity. Radiologic clinics of North America Braun, H. J., Dragoo, J. L., Hargreaves, B. A., Levenston, M. E., Gold, G. E. 2013; 51 (3): 529-545

    Abstract

    This article reviews current magnetic resonance imaging (MR imaging) techniques for imaging the lower extremity, focusing on imaging of the knee, ankle, and hip joints. Recent advancements in MR imaging include imaging at 7 T, using multiple receiver channels, T2* imaging, and metal suppression techniques, allowing more detailed visualization of complex anatomy, evaluation of morphologic changes within articular cartilage, and imaging around orthopedic hardware.

    View details for DOI 10.1016/j.rcl.2012.12.001

    View details for PubMedID 23622097

    View details for PubMedCentralID PMC3639445

  • Subject-specific models of susceptibility-induced B0 field variations in breast MRI JOURNAL OF MAGNETIC RESONANCE IMAGING Jordan, C. D., Daniel, B. L., Koch, K. M., Yu, H., Conolly, S., Hargreaves, B. A. 2013; 37 (1): 227-232

    Abstract

    To rapidly calculate and validate subject-specific field maps based on the three-dimensional shape of the bilateral breast volume.Ten healthy female volunteers were scanned at 3 Tesla using a multi-echo sequence that provides water, fat, in-phase, out-of-phase, and field map images. A shape-specific binary mask was automatically generated to calculate a computed field map using a dipole field model. The measured and computed field maps were compared by visualizing the spatial distribution of the difference field map, the mean absolute error, and the 80% distribution widths of frequency histograms.The 10 computed field maps had a mean absolute error of 38 Hz (0.29 ppm) compared with the measured field maps. The average 80% distribution widths for the histograms of all of the computed, measured, and difference field maps are 205 Hz, 233 Hz, and 120 Hz, respectively.The computed field maps had substantial overall agreement with the measured field maps, indicating that breast MRI field maps can be computed based on the air-tissue interfaces. These estimates may provide a predictive model for field variations and thus have the potential to improve applications in breast MRI.

    View details for DOI 10.1002/jmri.23762

    View details for Web of Science ID 000312720000025

    View details for PubMedID 22865658

    View details for PubMedCentralID PMC3492544

  • Compressed-Sensing multispectral imaging of the postoperative spine JOURNAL OF MAGNETIC RESONANCE IMAGING Worters, P. W., Sung, K., Stevens, K. J., Koch, K. M., Hargreaves, B. A. 2013; 37 (1): 243-248

    Abstract

    To apply compressed sensing (CS) to in vivo multispectral imaging (MSI), which uses additional encoding to avoid magnetic resonance imaging (MRI) artifacts near metal, and demonstrate the feasibility of CS-MSI in postoperative spinal imaging.Thirteen subjects referred for spinal MRI were examined using T2-weighted MSI. A CS undersampling factor was first determined using a structural similarity index as a metric for image quality. Next, these fully sampled datasets were retrospectively undersampled using a variable-density random sampling scheme and reconstructed using an iterative soft-thresholding method. The fully and undersampled images were compared using a 5-point scale. Prospectively undersampled CS-MSI data were also acquired from two subjects to ensure that the prospective random sampling did not affect the image quality.A two-fold outer reduction factor was deemed feasible for the spinal datasets. CS-MSI images were shown to be equivalent or better than the original MSI images in all categories: nerve visualization: P = 0.00018; image artifact: P = 0.00031; image quality: P = 0.0030. No alteration of image quality and T2 contrast was observed from prospectively undersampled CS-MSI.This study shows that the inherently sparse nature of MSI data allows modest undersampling followed by CS reconstruction with no loss of diagnostic quality.

    View details for DOI 10.1002/jmri.23750

    View details for Web of Science ID 000312720000028

    View details for PubMedID 22791572

    View details for PubMedCentralID PMC3473176

  • Evaluation of 3D T2-weighted Breast MRI Moran, C. J., Hargreaves, B. A., Saranathan, M., Daniel, B. L. AMER ASSOC CANCER RESEARCH. 2012

    View details for DOI 10.1158/0008-5472.SABCS12-P4-01-06

    View details for Web of Science ID 000209704900474

  • Rapid gradient-echo imaging JOURNAL OF MAGNETIC RESONANCE IMAGING Hargreaves, B. A. 2012; 36 (6): 1300-1313

    Abstract

    Gradient-echo sequences are widely used in magnetic resonance imaging (MRI) for numerous applications ranging from angiography to perfusion to functional MRI. Compared with spin-echo techniques, the very short repetition times of gradient-echo methods enable very rapid 2D and 3D imaging, but also lead to complicated "steady states." Signal and contrast behavior can be described graphically and mathematically, and depends strongly on the type of spoiling: fully balanced (no spoiling), gradient spoiling, or radiofrequency (RF)-spoiling. These spoiling options trade off between high signal and pure T(1) contrast, while the flip angle also affects image contrast in all cases, both of which can be demonstrated theoretically and in image examples. As with spin-echo sequences, magnetization preparation can be added to gradient-echo sequences to alter image contrast. Gradient-echo sequences are widely used for numerous applications such as 3D perfusion imaging, functional MRI, cardiac imaging, and MR angiography.

    View details for DOI 10.1002/jmri.23742

    View details for Web of Science ID 000311381900004

    View details for PubMedID 23097185

    View details for PubMedCentralID PMC3502662

  • Advances in musculoskeletal MRI: Technical considerations JOURNAL OF MAGNETIC RESONANCE IMAGING Shapiro, L., Harish, M., Hargreaves, B., Staroswiecki, E., Gold, G. 2012; 36 (4): 775-787

    Abstract

    The technology of musculoskeletal magnetic resonance imaging (MRI) is advancing at a dramatic rate. MRI is now done at medium and higher field strengths with more specialized surface coils and with more variable pulse sequences and postprocessing techniques than ever before. These innumerable technical advances are advantageous as they lead to an increased signal-to-noise ratio and increased variety of soft-tissue contrast options. However, at the same time they potentially produce more imaging artifacts when compared with past techniques. Substantial technical advances have considerable clinical challenges in musculoskeletal radiology such as postoperative patient imaging, cartilage mapping, and molecular imaging. In this review we consider technical advances in hardware and software of musculoskeletal MRI along with their clinical applications.

    View details for DOI 10.1002/jmri.23629

    View details for Web of Science ID 000308884300002

    View details for PubMedID 22987756

    View details for PubMedCentralID PMC3448292

  • Metals in MR-mammography: how to deal with it? European journal of radiology Hargreaves, B. A., Daniel, B. L. 2012; 81: S56-8

    View details for DOI 10.1016/S0720-048X(12)70021-9

    View details for PubMedID 23083602

  • Accelerated breast MRI with compressed sensing. European journal of radiology Hargreaves, B. A., Saranathan, M., Sung, K., Daniel, B. L. 2012; 81: S54-5

    View details for DOI 10.1016/S0720-048X(12)70020-7

    View details for PubMedID 23083601

  • High resolution images of the breast. European journal of radiology Moran, C. J., Saranathan, M., Nnewihe, A. N., Granlund, K. L., Alley, M. T., Daniel, B. L., Hargreaves, B. A. 2012; 81: S101-3

    View details for DOI 10.1016/S0720-048X(12)70041-4

    View details for PubMedID 23083546

  • Breast MRI without gadolinium: utility of 3D DESS, a new 3D diffusion weighted gradient-echo sequence. European journal of radiology Daniel, B. L., Granlund, K. L., Moran, C. J., Alley, M. T., Lipson, J., Ikeda, D. M., Kao, J., Hargreaves, B. A. 2012; 81: S24-6

    View details for DOI 10.1016/S0720-048X(12)70010-4

    View details for PubMedID 23083590

  • DIfferential subsampling with cartesian ordering (DISCO): A high spatio-temporal resolution dixon imaging sequence for multiphasic contrast enhanced abdominal imaging JOURNAL OF MAGNETIC RESONANCE IMAGING Saranathan, M., Rettmann, D. W., Hargreaves, B. A., Clarke, S. E., Vasanawala, S. S. 2012; 35 (6): 1484-1492

    Abstract

    To develop and evaluate a multiphasic contrast-enhanced MRI method called DIfferential Sub-sampling with Cartesian Ordering (DISCO) for abdominal imaging.A three-dimensional, variable density pseudo-random k-space segmentation scheme was developed and combined with a Dixon-based fat-water separation algorithm to generate high temporal resolution images with robust fat suppression and without compromise in spatial resolution or coverage. With institutional review board approval and informed consent, 11 consecutive patients referred for abdominal MRI at 3 Tesla (T) were imaged with both DISCO and a routine clinical three-dimensional SPGR-Dixon (LAVA FLEX) sequence. All images were graded by two radiologists using quality of fat suppression, severity of artifacts, and overall image quality as scoring criteria. For assessment of arterial phase capture efficiency, the number of temporal phases with angiographic phase and hepatic arterial phase was recorded.There were no significant differences in quality of fat suppression, artifact severity or overall image quality between DISCO and LAVA FLEX images (P > 0.05, Wilcoxon signed rank test). The angiographic and arterial phases were captured in all 11 patients scanned using the DISCO acquisition (mean number of phases were two and three, respectively).DISCO effectively captures the fast dynamics of abdominal pathology such as hyperenhancing hepatic lesions with a high spatio-temporal resolution. Typically, 1.1 × 1.5 × 3 mm spatial resolution over 60 slices was achieved with a temporal resolution of 4-5 s.

    View details for DOI 10.1002/jmri.23602

    View details for Web of Science ID 000304035100028

    View details for PubMedID 22334505

    View details for PubMedCentralID PMC3354015

  • Simultaneous Fat Suppression and Band Reduction with Large-Angle Multiple-Acquisition Balanced Steady-State Free Precession MAGNETIC RESONANCE IN MEDICINE Quist, B., Hargreaves, B. A., Cukur, T., Morrell, G. R., Gold, G. E., Bangerter, N. K. 2012; 67 (4): 1004-1012

    Abstract

    Balanced steady-state free precession (bSSFP) MRI is a rapid and signal-to-noise ratio-efficient imaging method, but suffers from characteristic bands of signal loss in regions of large field inhomogeneity. Several methods have been developed to reduce the severity of these banding artifacts, typically involving the acquisition of multiple bSSFP datasets (and the accompanying increase in scan time). Fat suppression with bSSFP is also challenging; most existing methods require an additional increase in scan time, and some are incompatible with bSSFP band-reduction techniques. This work was motivated by the need for both robust fat suppression and band reduction in the presence of field inhomogeneity when using bSSFP for flow-independent peripheral angiography. The large flip angles used in this application to improve vessel conspicuity and contrast lead to specific absorption rate considerations, longer repetition times, and increased severity of banding artifacts. In this work, a novel method that simultaneously suppresses fat and reduces bSSFP banding artifact with the acquisition of only two phase-cycled bSSFP datasets is presented. A weighted sum of the two bSSFP acquisitions is taken on a voxel-by-voxel basis, effectively synthesizing an off-resonance profile at each voxel that puts fat in the stop band while keeping water in the pass band. The technique exploits the near-sinusoidal shape of the bSSFP off-resonance spectrum for many tissues at large (>50°) flip angles.

    View details for DOI 10.1002/mrm.23076

    View details for Web of Science ID 000301533500014

    View details for PubMedID 22038883

    View details for PubMedCentralID PMC3306491

  • Simultaneous Estimation of T-2 and Apparent Diffusion Coefficient in Human Articular Cartilage In Vivo with a Modified Three-Dimensional Double Echo Steady State (DESS) Sequence at 3 T MAGNETIC RESONANCE IN MEDICINE Staroswiecki, E., Granlund, K. L., Alley, M. T., Gold, G. E., Hargreaves, B. A. 2012; 67 (4): 1086-1096

    Abstract

    T(2) mapping and diffusion-weighted imaging complement morphological imaging for assessing cartilage disease and injury. The double echo steady state sequence has been used for morphological imaging and generates two echoes with markedly different T(2) and diffusion weighting. Modifying the spoiler gradient area and flip angle of the double echo steady state sequence allows greater control of the diffusion weighting of both echoes. Data from two acquisitions with different spoiler gradient areas and flip angles are used to simultaneously estimate the T(2) and apparent diffusion coefficient of each voxel. This method is verified in phantoms and validated in vivo in the knee; estimates from different regions of interest in the phantoms and cartilage are compared to those obtained using standard spin-echo methods. The Pearson correlations were 0.984 for T(2) (∼2% relative difference between spin-echo and double echo steady state estimates) and 0.997 for apparent diffusion coefficient (˜1% relative difference between spin-echo and double echo steady state estimates) for the phantom study and 0.989 for T(2) and 0.987 for apparent diffusion coefficient in regions of interest in the human knee in vivo. High accuracy for simultaneous three-dimensional T(2) and apparent diffusion coefficient measurements are demonstrated, while also providing morphologic three-dimensional images without blurring or distortion in reasonable scan times.

    View details for DOI 10.1002/mrm.23090

    View details for Web of Science ID 000301533500022

    View details for PubMedID 22179942

    View details for PubMedCentralID PMC3306505

  • High Spatio-Temporal Resolution Dynamic Contrast-Enhnaced MRI using Compressed Sensing Annual Summit and Conference of the Asia-Pacific-Signal-and-Information-Processing-Association (APSIPA) Sung, K., Saranathan, M., Daniel, B. L., Hargreaves, B. A. IEEE. 2012

    View details for Web of Science ID 000319456200248

  • Three-dimensional fluid-suppressed T2-prep flow-independent peripheral angiography using balanced SSFP MAGNETIC RESONANCE IMAGING Bangerter, N. K., Cukur, T., Hargreaves, B. A., Hu, B. S., Brittain, J. H., Park, D., Gold, G. E., Nishimura, D. G. 2011; 29 (8): 1119-1124

    Abstract

    Accurate depiction of the vessels of the lower leg, foot or hand benefits from suppression of bright MR signal from lipid (such as bone marrow) and long-T1 fluid (such as synovial fluid and edema). Signal independence of blood flow velocities, good arterial/muscle contrast and arterial/venous separation are also desirable. The high SNR, short scan times and flow properties of balanced steady-state free precession (SSFP) make it an excellent candidate for flow-independent angiography. In this work, a new magnetization-prepared 3D SSFP sequence for flow-independent peripheral angiography is presented. The technique combines a number of component techniques (phase-sensitive fat detection, inversion recovery, T2-preparation and square-spiral phase-encode ordering) to achieve high-contrast peripheral angiograms at only a modest scan time penalty over simple 3D SSFP. The technique is described in detail, a parameter optimization performed and preliminary results presented achieving high contrast and 1-mm isotropic resolution in a normal foot.

    View details for DOI 10.1016/j.mri.2011.04.007

    View details for Web of Science ID 000295195900011

    View details for PubMedID 21705166

    View details for PubMedCentralID PMC3172338

  • Metal-Induced Artifacts in MRI AMERICAN JOURNAL OF ROENTGENOLOGY Hargreaves, B. A., Worters, P. W., Pauly, K. B., Pauly, J. M., Koch, K. M., Gold, G. E. 2011; 197 (3): 547-555

    Abstract

    The purpose of this article is to review some of the basic principles of imaging and how metal-induced susceptibility artifacts originate in MR images. We will describe common ways to reduce or modify artifacts using readily available imaging techniques, and we will discuss some advanced methods to correct readout-direction and slice-direction artifacts.The presence of metallic implants in MRI can cause substantial image artifacts, including signal loss, failure of fat suppression, geometric distortion, and bright pile-up artifacts. These cause large resonant frequency changes and failure of many MRI mechanisms. Careful parameter and pulse sequence selections can avoid or reduce artifacts, although more advanced imaging methods offer further imaging improvements.

    View details for DOI 10.2214/AJR.11.7364

    View details for Web of Science ID 000294165600037

    View details for PubMedID 21862795

  • Custom-Fitted 16-Channel Bilateral Breast Coil for Bidirectional Parallel Imaging MAGNETIC RESONANCE IN MEDICINE Nnewihe, A. N., Grafendorfer, T., Daniel, B. L., Calderon, P., Alley, M. T., Robb, F., Hargreaves, B. A. 2011; 66 (1): 281-289

    Abstract

    A 16-channel receive-only, closely fitted array coil is described and tested in vivo for bilateral breast imaging at 3 T. The primary purpose of this coil is to provide high signal-to-noise ratio and parallel imaging acceleration in two directions for breast MRI. Circular coil elements (7.5-cm diameter) were placed on a closed "cup-shaped" platform, and nearest neighbor coils were decoupled through geometric overlap. Comparisons were made between the 16-channel custom coil and a commercially available 8-channel coil. SENSitivity Encoding (SENSE) parallel imaging noise amplification (g-factor) was evaluated in phantom scans. In healthy volunteers, we compared signal-to-noise ratio, parallel imaging in one and two directions, Autocalibrating Reconstruction for Cartesian sampling (ARC) g-factor, and high spatial resolution imaging. When compared with a commercially available 8-channel coil, the 16-channel custom coil shows 3.6× higher mean signal-to-noise ratio in the breast and higher quality accelerated images. In patients, the 16-channel custom coil has facilitated high-quality, high-resolution images with bidirectional acceleration of R = 6.3.

    View details for DOI 10.1002/mrm.22771

    View details for Web of Science ID 000292425100034

    View details for PubMedID 21287593

    View details for PubMedCentralID PMC3128917

  • Slice Encoding for Metal Artifact Correction With Noise Reduction MAGNETIC RESONANCE IN MEDICINE Lu, W., Pauly, K. B., Gold, G. E., Pauly, J. M., Hargreaves, B. A. 2011; 65 (5): 1352-1357

    Abstract

    Magnetic resonance imaging (MRI) near metallic implants is often hampered by severe metal artifacts. To obtain distortion-free MR images near metallic implants, SEMAC (Slice Encoding for Metal Artifact Correction) corrects metal artifacts via robust encoding of excited slices against metal-induced field inhomogeneities, followed by combining the data resolved from multiple SEMAC-encoded slices. However, as many of the resolved data elements only contain noise, SEMAC-corrected images can suffer from relatively low signal-to-noise ratio. Improving the signal-to-noise ratio of SEMAC-corrected images is essential to enable SEMAC in routine clinical studies. In this work, a new reconstruction procedure is proposed to reduce noise in SEMAC-corrected images. A singular value decomposition denoising step is first applied to suppress quadrature noise in multi-coil SEMAC-encoded slices. Subsequently, the singular value decomposition-denoised data are selectively included in the correction of through-plane distortions. The experimental results demonstrate that the proposed reconstruction procedure significantly improves the SNR without compromising the correction of metal artifacts.

    View details for DOI 10.1002/mrm.22796

    View details for Web of Science ID 000289760800018

    View details for PubMedID 21287596

    View details for PubMedCentralID PMC3079010

  • Reduction of Flow Artifacts by Using Partial Saturation in RF-Spoiled Gradient-Echo Imaging MAGNETIC RESONANCE IN MEDICINE Han, M., Hargreaves, B. A. 2011; 65 (5): 1326-1334

    Abstract

    Radiofrequency (RF)-spoiled gradient-echo imaging provides a signal intensity close to pure T(1) contrast by using spoiler gradients and RF phase cycling to eliminate net transverse magnetization. Generally, spins require many RF excitations to reach a steady-state magnetization level; therefore, when unsaturated flowing spins enter the imaging slab, they can cause undesirable signal enhancement and generate image artifacts. These artifacts can be reduced by partially saturating an outer slab upstream to drive the longitudinal magnetization close to the steady state, while the partially saturated spins generate no signal until they enter the imaging slab. In this work, magnetization evolution of flowing spins in RF-spoiled gradient-echo sequences with and without partial saturation was simulated using the Bloch equations. Next, the simulations were validated by phantom and in vivo experiments. For phantom experiments, a pulsatile flow phantom was used to test partial saturation for a range of flip angles and relaxation times. For in vivo experiments, the technique was used to image the carotid arteries, abdominal aorta, and femoral arteries of normal volunteers. All experiments demonstrated that partial saturation can provide consistent T(1) contrast across the slab while reducing inflow artifacts.

    View details for DOI 10.1002/mrm.22729

    View details for Web of Science ID 000289760800015

    View details for PubMedID 21319219

    View details for PubMedCentralID PMC3525091

  • New MR Imaging Methods for Metallic Implants in the Knee: Artifact Correction and Clinical Impact JOURNAL OF MAGNETIC RESONANCE IMAGING Chen, C. A., Chen, W., Goodman, S. B., Hargreaves, B. A., Koch, K. M., Lu, W., Brau, A. C., Draper, C. E., Delp, S. L., Gold, G. E. 2011; 33 (5): 1121-1127

    Abstract

    To evaluate two magnetic resonance imaging (MRI) techniques, slice encoding for metal artifact correction (SEMAC) and multiacquisition variable-resonance image combination (MAVRIC), for their ability to correct for artifacts in postoperative knees with metal.A total of 25 knees were imaged in this study. Fourteen total knee replacements (TKRs) in volunteers were scanned with SEMAC, MAVRIC, and 2D fast spin-echo (FSE) to measure artifact extent and implant rotation. The ability of the sequences to measure implant rotation and dimensions was compared in a TKR knee model. Eleven patients with a variety of metallic hardware were imaged with SEMAC and FSE to compare artifact extent and subsequent patient management was recorded.SEMAC and MAVRIC significantly reduced artifact extent compared to FSE (P < 0.0001) and were similar to each other (P = 0.58), allowing accurate measurement of implant dimensions and rotation. The TKRs were properly aligned in the volunteers. Clinical imaging with SEMAC in symptomatic knees significantly reduced artifact (P < 0.05) and showed findings that were on the majority confirmed by subsequent noninvasive or invasive patient studies.SEMAC and MAVRIC correct for metal artifact, noninvasively providing high-resolution images with superb bone and soft tissue contrast.

    View details for DOI 10.1002/jmri.22534

    View details for Web of Science ID 000289999700015

    View details for PubMedID 21509870

    View details for PubMedCentralID PMC3081101

  • Magnetization-Prepared IDEAL bSSFP: A Flow-Independent Technique for Noncontrast-Enhanced Peripheral Angiography JOURNAL OF MAGNETIC RESONANCE IMAGING Cukur, T., Shimakawa, A., Yu, H., Hargreaves, B. A., Hu, B. S., Nishimura, D. G., Brittain, J. H. 2011; 33 (4): 931-939

    Abstract

    To propose a new noncontrast-enhanced flow-independent angiography sequence based on balanced steady-state free precession (bSSFP) that produces reliable vessel contrast despite the reduced blood flow in the extremities.The proposed technique addresses a variety of factors that can compromise the exam success including insufficient background suppression, field inhomogeneity, and large volumetric coverage requirements. A bSSFP sequence yields reduced signal from venous blood when long repetition times are used. Complex-sum bSSFP acquisitions decrease the sensitivity to field inhomogeneity but retain phase information, so that data can be processed with the Iterative Decomposition of Water and Fat with Echo Asymmetry and Least-Squares Estimation (IDEAL) method for robust fat suppression. Meanwhile, frequent magnetization preparation coupled with parallel imaging reduces the muscle and long-T(1) fluid signals without compromising scan efficiency.In vivo flow-independent peripheral angiograms with reliable background suppression and high spatial resolution are produced. Comparisons with phase-sensitive bSSFP angiograms (that yield out-of-phase fat and water signals, and exploit this phase difference to suppress fat) demonstrate enhanced vessel depiction with the proposed technique due to reduced partial-volume effects and improved venous suppression.Magnetization-prepared complex-sum bSSFP with IDEAL fat/water separation can create reliable flow-independent angiographic contrast in the lower extremities.

    View details for DOI 10.1002/jmri.22479

    View details for Web of Science ID 000288913200022

    View details for PubMedID 21448960

    View details for PubMedCentralID PMC3155993

  • MR Water Quantitative Priors Improves the Accuracy of Optical Breast Imaging IEEE TRANSACTIONS ON MEDICAL IMAGING Carpenter, C. M., Pogue, B. W., Jiang, S., Wang, J., Hargreaves, B. A., Rakow-Penner, R., Daniel, B. L., Paulsen, K. D. 2011; 30 (1): 159-168

    Abstract

    Magnetic resonance (MR) guided optical breast imaging is a promising modality to improve the specificity of breast imaging, because it provides high-resolution quantitative maps of total hemoglobin, oxygen saturation, water content, and optical scattering. These properties have been shown to distinguish malignant from benign lesions. However, the optical detection hardware required for deep tissue imaging has poor spectral sensitivity which limits accurate water quantification; this reduces the accuracy of hemoglobin quantification. We present a methodology to improve optical quantification by utilizing the ability of Dixon MR imaging to quantitatively estimate water and fat; this technique effectively reduces optical crosstalk between water and oxyhemoglobin. The techniques described in this paper reduce hemoglobin quantification error by as much as 38%, as shown in a numerical phantom, and an experimental phantom. Error is reduced by as much 20% when imperfect MR water quantification is given. These techniques may also increase contrast between diseased and normal tissue, as shown in breast tissue in vivo. It is also shown that using these techniques may permit fewer wavelengths to be used with similar quantitative accuracy, enabling higher temporal resolution. In addition, it is shown that these techniques can improve the ability of MRI to quantify water in the presence of bias in the Dixon water/fat separation.

    View details for DOI 10.1109/TMI.2010.2071394

    View details for Web of Science ID 000285844900014

    View details for PubMedID 20813635

    View details for PubMedCentralID PMC3774063

  • Imaging Near Metal with a MAVRIC-SEMAC Hybrid MAGNETIC RESONANCE IN MEDICINE Koch, K. M., Brau, A. C., Chen, W., Gold, G. E., Hargreaves, B. A., Koff, M., McKinnon, G. C., Potter, H. G., King, K. F. 2011; 65 (1): 71-82

    Abstract

    The recently developed multi-acquisition with variable resonance image combination (MAVRIC) and slice-encoding metal artifact correction (SEMAC) techniques can significantly reduce image artifacts commonly encountered near embedded metal hardware. These artifact reductions are enabled by applying alternative spectral and spatial-encoding schemes to conventional spin-echo imaging techniques. Here, the MAVRIC and SEMAC concepts are connected and discussed. The development of a hybrid technique that utilizes strengths of both methods is then introduced. The presented technique is shown capable of producing minimal artifact, high-resolution images near total joint replacements in a clinical setting.

    View details for DOI 10.1002/mrm.22523

    View details for Web of Science ID 000285963500009

    View details for PubMedID 20981709

  • Balanced SSFP transient imaging using variable flip angles for a predefined signal profile. Magnetic resonance in medicine Worters, P. W., Hargreaves, B. A. 2010; 64 (5): 1404-1412

    Abstract

    Variable flip angles are used in steady-state free precession (SSFP) acquisitions (e.g., time-of-flight) but to a lesser extent than in spin echo acquisitions. In balanced steady-state free precession, imaging is often assumed to occur during the steady state, which has been well described in the literature. However, in many cases, imaging occurs during the transient stage, and the use of variable flip angles can improve signal and thus image quality. Here, we present the calculation of flip angles in transient balanced steady-state free precession to generate a predefined signal profile. The signal profile was iteratively optimized to maximize the integral of the signal versus time curve. The key contribution of this work is the formulation of the flip angle as a deterministic function of the preceding and desired magnetization. Catalyzation schemes, e.g., Kaiser-windowed ramp, can be combined with variable flip angles balanced steady-state free precession to reduce signal oscillations. A uniform signal profile was used as an example to demonstrate the variable flip angle algorithm. Accuracy of the algorithm and Bloch simulations were verified with MRI phantom acquisitions. Renal angiograms were acquired using an inflow-based balanced steady-state free precession MR angiography technique; improved small-vessel depiction was observed in volunteer examinations.

    View details for DOI 10.1002/mrm.22541

    View details for PubMedID 20632411

  • Balanced SSFP Transient Imaging Using Variable Flip Angles for a Predefined Signal Profile MAGNETIC RESONANCE IN MEDICINE Worters, P. W., Hargreaves, B. A. 2010; 64 (5): 1405-1413

    Abstract

    Variable flip angles are used in steady-state free precession (SSFP) acquisitions (e.g., time-of-flight) but to a lesser extent than in spin echo acquisitions. In balanced steady-state free precession, imaging is often assumed to occur during the steady state, which has been well described in the literature. However, in many cases, imaging occurs during the transient stage, and the use of variable flip angles can improve signal and thus image quality. Here, we present the calculation of flip angles in transient balanced steady-state free precession to generate a predefined signal profile. The signal profile was iteratively optimized to maximize the integral of the signal versus time curve. The key contribution of this work is the formulation of the flip angle as a deterministic function of the preceding and desired magnetization. Catalyzation schemes, e.g., Kaiser-windowed ramp, can be combined with variable flip angles balanced steady-state free precession to reduce signal oscillations. A uniform signal profile was used as an example to demonstrate the variable flip angle algorithm. Accuracy of the algorithm and Bloch simulations were verified with MRI phantom acquisitions. Renal angiograms were acquired using an inflow-based balanced steady-state free precession MR angiography technique; improved small-vessel depiction was observed in volunteer examinations.

    View details for DOI 10.1002/mrm.22541

    View details for Web of Science ID 000283616900020

    View details for PubMedCentralID PMC2965793

  • Fabrication of custom-shaped grafts for cartilage regeneration INTERNATIONAL JOURNAL OF ARTIFICIAL ORGANS Koo, S., Hargreaves, B. A., Gold, G. E., Dragoo, J. L. 2010; 33 (10): 731-737

    Abstract

    to create a custom-shaped graft through 3D tissue shape reconstruction and rapid-prototype molding methods using MRI data, and to test the accuracy of the custom-shaped graft against the original anatomical defect.An iatrogenic defect on the distal femur was identified with a 1.5 Tesla MRI and its shape was reconstructed into a three-dimensional (3D) computer model by processing the 3D MRI data. First, the accuracy of the MRI-derived 3D model was tested against a laser-scan based 3D model of the defect. A custom-shaped polyurethane graft was fabricated from the laser-scan based 3D model by creating custom molds through computer aided design and rapid-prototyping methods. The polyurethane tissue was laser-scanned again to calculate the accuracy of this process compared to the original defect.The volumes of the defect models from MRI and laser-scan were 537 mm3 and 405 mm3, respectively, implying that the MRI model was 33% larger than the laser-scan model. The average (±SD) distance deviation of the exterior surface of the MRI model from the laser-scan model was 0.4 ± 0.4 mm. The custom-shaped tissue created from the molds was qualitatively very similar to the original shape of the defect. The volume of the custom-shaped cartilage tissue was 463 mm3 which was 15% larger than the laser-scan model. The average (±SD) distance deviation between the two models was 0.04 ± 0.19 mm.This investigation proves the concept that custom-shaped engineered grafts can be fabricated from standard sequence 3-D MRI data with the use of CAD and rapid-prototyping technology. The accuracy of this technology may help solve the interfacial problem between native cartilage and graft, if the grafts are custom made for the specific defect. The major source of error in fabricating a 3D custom-shaped cartilage graft appears to be the accuracy of a MRI data itself; however, the precision of the model is expected to increase by the utilization of advanced MR sequences with higher magnet strengths.

    View details for Web of Science ID 000284234600006

    View details for PubMedID 21058268

    View details for PubMedCentralID PMC3310388

  • Advances in musculoskeletal magnetic resonance imaging. Topics in magnetic resonance imaging Gold, G., Shapiro, L., Hargreaves, B., Bangerter, N. 2010; 21 (5): 335-338

    Abstract

    The technology of musculoskeletal magnetic resonance imaging is advancing at a dramatic rate. Magnetic resonance imaging is now done at medium and higher field strengths with more specialized surface coils and with more variable pulse sequences and postprocessing techniques than ever before. These numerable technical advances are advantageous because they lead to an increased signal-to-noise ratio and increased variety of soft tissue contrast options. However, at the same time, they potentially produce more imaging artifacts when compared with past techniques. Substantial technical advances have considerable clinical challenges in musculoskeletal radiology such as postoperative patient imaging, cartilage mapping, and molecular imaging. In this review, we consider technical advances in hardware and software of musculoskeletal magnetic resonance imaging along with their clinical applications.

    View details for DOI 10.1097/RMR.0b013e31823cd195

    View details for PubMedID 22129646

  • Magnetic Resonance Imaging Near Metal Implants JOURNAL OF MAGNETIC RESONANCE IMAGING Koch, K. M., Hargreaves, B. A., Pauly, K. B., Chen, W., Gold, G. E., King, K. F. 2010; 32 (4): 773-787

    Abstract

    The desire to apply magnetic resonance imaging (MRI) techniques in the vicinity of embedded metallic hardware is increasing. The soft-tissue contrast available with MR techniques is advantageous in diagnosing complications near an increasing variety of MR-safe metallic hardware. Near such hardware, the spatial encoding mechanisms utilized in conventional MRI methods are often severely compromised. Mitigating these encoding difficulties has been the focus of numerous research investigations over the past two decades. Such approaches include view-angle tilting, short echo-time projection reconstruction acquisitions, single-point imaging, prepolarized MRI, and postprocessing image correction. Various technical advances have also enabled the recent development of two alternative approaches that have shown promising clinical potential. Here, the physical principals and proposed solutions to the problem of MRI near embedded metal are discussed.

    View details for DOI 10.1002/jmri.22313

    View details for Web of Science ID 000282764800002

    View details for PubMedID 20882607

  • Pyrolytic Graphite Foam: A Passive Magnetic Susceptibility Matching Material JOURNAL OF MAGNETIC RESONANCE IMAGING Lee, G. C., Goodwill, P. W., Phuong, K., Inglis, B. A., Scott, G. C., Hargreaves, B. A., Li, L., Chen, A. C., Shah, R. N., Conolly, S. M. 2010; 32 (3): 684-691

    Abstract

    To evaluate a novel soft, lightweight cushion that can match the magnetic susceptibility of human tissue. The magnetic susceptibility difference between air and tissue produces field inhomogeneities in the B(0) field, which leads to susceptibility artifacts in magnetic resonance imaging (MRI) studies.Pyrolytic graphite (PG) microparticles were uniformly embedded into a foam cushion to reduce or eliminate field inhomogeneities at accessible air and tissue interfaces. 3T MR images and field maps of an air/water/PG foam phantom were acquired. Q measurements on a 4T tuned head coil and pulse sequence heating tests at 3T were also performed.The PG foam improved susceptibility matching, reduced the field perturbations in phantoms, does not heat, and is nonconductive.The susceptibility matched PG foam is lightweight, safe for patient use, adds no noise or MRI artifacts, is compatible with radiofrequency coil arrays, and improves B(0) homogeneity, which enables more robust MR studies.

    View details for DOI 10.1002/jmri.22270

    View details for Web of Science ID 000281532700019

    View details for PubMedID 20815067

    View details for PubMedCentralID PMC3525090

  • Improved Pediatric MR Imaging with Compressed Sensing RADIOLOGY Vasanawala, S. S., Alley, M. T., Hargreaves, B. A., Barth, R. A., Pauly, J. M., Lustig, M. 2010; 256 (2): 607-616

    Abstract

    To develop a method that combines parallel imaging and compressed sensing to enable faster and/or higher spatial resolution magnetic resonance (MR) imaging and show its feasibility in a pediatric clinical setting.Institutional review board approval was obtained for this HIPAA-compliant study, and informed consent or assent was given by subjects. A pseudorandom k-space undersampling pattern was incorporated into a three-dimensional (3D) gradient-echo sequence; aliasing then has an incoherent noiselike pattern rather than the usual coherent fold-over wrapping pattern. This k-space-sampling pattern was combined with a compressed sensing nonlinear reconstruction method that exploits the assumption of sparsity of medical images to permit reconstruction from undersampled k-space data and remove the noiselike aliasing. Thirty-four patients (15 female and 19 male patients; mean age, 8.1 years; range, 0-17 years) referred for cardiovascular, abdominal, and knee MR imaging were scanned with this 3D gradient-echo sequence at high acceleration factors. Obtained k-space data were reconstructed with both a traditional parallel imaging algorithm and the nonlinear method. Both sets of images were rated for image quality, radiologist preference, and delineation of specific structures by two radiologists. Wilcoxon and symmetry tests were performed to test the hypothesis that there was no significant difference in ratings for image quality, preference, and delineation of specific structures.Compressed sensing images were preferred more often, had significantly higher image quality ratings, and greater delineation of anatomic structures (P < .001) than did images obtained with the traditional parallel reconstruction method.A combination of parallel imaging and compressed sensing is feasible in a clinical setting and may provide higher resolution and/or faster imaging, addressing the challenge of delineating anatomic structures in pediatric MR imaging.

    View details for DOI 10.1148/radiol.10091218

    View details for Web of Science ID 000280272100032

    View details for PubMedID 20529991

    View details for PubMedCentralID PMC2909438

  • In Vivo Sodium Imaging of Human Patellar Cartilage With a 3D Cones Sequence at 3 T and 7 T JOURNAL OF MAGNETIC RESONANCE IMAGING Staroswiecki, E., Bangerter, N. K., Gurney, P. T., Grafendorfer, T., Gold, G. E., Hargreaves, B. A. 2010; 32 (2): 446-451

    Abstract

    To compare signal-to-noise ratios (SNRs) and T*(2) maps at 3 T and 7 T using 3D cones from in vivo sodium images of the human knee.Sodium concentration has been shown to correlate with glycosaminoglycan content of cartilage and is a possible biomarker of osteoarthritis. Using a 3D cones trajectory, 17 subjects were scanned at 3 T and 12 at 7 T using custom-made sodium-only and dual-tuned sodium/proton surface coils, at a standard resolution (1.3 x 1.3 x 4.0 mm(3)) and a high resolution (1.0 x 1.0 x 2.0 mm(3)). We measured the SNR of the images and the T*(2) of cartilage at both 3 T and 7 T.The average normalized SNR values of standard-resolution images were 27.1 and 11.3 at 7 T and 3 T. At high resolution, these average SNR values were 16.5 and 7.3. Image quality was sufficient to show spatial variations of sodium content. The average T*(2) of cartilage was measured as 13.2 +/- 1.5 msec at 7 T and 15.5 +/- 1.3 msec at 3 T.We acquired sodium images of patellar cartilage at 3 T and 7 T in under 26 minutes using 3D cones with high resolution and acceptable SNR. The SNR improvement at 7 T over 3 T was within the expected range based on the increase in field strength. The measured T*(2) values were also consistent with previously published values.

    View details for DOI 10.1002/jmri.22191

    View details for Web of Science ID 000280447300028

    View details for PubMedID 20677276

    View details for PubMedCentralID PMC3008581

  • Accelerated Slice Encoding for Metal Artifact Correction JOURNAL OF MAGNETIC RESONANCE IMAGING Hargreaves, B. A., Chen, W., Lu, W., Alley, M. T., Gold, G. E., Brau, A. C., Pauly, J. M., Pauly, K. B. 2010; 31 (4): 987-996

    Abstract

    To demonstrate accelerated imaging with both artifact reduction and different contrast mechanisms near metallic implants.Slice-encoding for metal artifact correction (SEMAC) is a modified spin echo sequence that uses view-angle tilting and slice-direction phase encoding to correct both in-plane and through-plane artifacts. Standard spin echo trains and short-TI inversion recovery (STIR) allow efficient PD-weighted imaging with optional fat suppression. A completely linear reconstruction allows incorporation of parallel imaging and partial Fourier imaging. The signal-to-noise ratio (SNR) effects of all reconstructions were quantified in one subject. Ten subjects with different metallic implants were scanned using SEMAC protocols, all with scan times below 11 minutes, as well as with standard spin echo methods.The SNR using standard acceleration techniques is unaffected by the linear SEMAC reconstruction. In all cases with implants, accelerated SEMAC significantly reduced artifacts compared with standard imaging techniques, with no additional artifacts from acceleration techniques. The use of different contrast mechanisms allowed differentiation of fluid from other structures in several subjects.SEMAC imaging can be combined with standard echo-train imaging, parallel imaging, partial-Fourier imaging, and inversion recovery techniques to offer flexible image contrast with a dramatic reduction of metal-induced artifacts in scan times under 11 minutes.

    View details for DOI 10.1002/jmri.22112

    View details for Web of Science ID 000276328200026

    View details for PubMedID 20373445

    View details for PubMedCentralID PMC2894155

  • Independent Slab-Phase Modulation Combined With Parallel Imaging in Bilateral Breast MRI MAGNETIC RESONANCE IN MEDICINE Han, M., Beatty, P. J., Daniel, B. L., Hargreaves, B. A. 2009; 62 (5): 1221-1231

    Abstract

    Independent slab-phase modulation allows three-dimensional imaging of multiple volumes without encoding the space between volumes, thus reducing scan time. Parallel imaging further accelerates data acquisition by exploiting coil sensitivity differences between volumes. This work compared bilateral breast image quality from self-calibrated parallel imaging reconstruction methods such as modified sensitivity encoding, generalized autocalibrating partially parallel acquisitions and autocalibrated reconstruction for Cartesian sampling (ARC) for data with and without slab-phase modulation. A study showed an improvement of image quality by incorporating slab-phase modulation. Geometry factors measured from phantom images were more homogenous and lower on average when slab-phase modulation was used for both mSENSE and GRAPPA reconstructions. The resulting improved signal-to-noise ratio (SNR) was validated for in vivo images as well using ARC instead of GRAPPA, illustrating average SNR efficiency increases in mSENSE by 5% and ARC by 8% based on region of interest analysis. Furthermore, aliasing artifacts from mSENSE reconstruction were reduced when slab-phase modulation was used. Overall, slab-phase modulation with parallel imaging improved image quality and efficiency for 3D bilateral breast imaging.

    View details for DOI 10.1002/mrm.22115

    View details for Web of Science ID 000271431200016

    View details for PubMedID 19780156

  • MRI GUIDANCE FOR ACCELERATED PARTIAL BREAST IRRADIATION IN PRONE POSITION: IMAGING PROTOCOL DESIGN AND EVALUATION 50th Annual Meeting of the American-Society-for-Therapeutic-Radiology-and-Oncology (ASTRO) Ahn, K., Hargreaves, B. A., Alley, M. T., Horst, K. C., Luxton, G., Daniel, B. L., Hristov, D. ELSEVIER SCIENCE INC. 2009: 285–93

    Abstract

    To design and evaluate a magnetic resonance imaging (MRI) protocol to be incorporated in the simulation process for external beam accelerated partial breast irradiation.An imaging protocol was developed based on an existing breast MRI technique with the patient in the prone position on a dedicated coil. Pulse sequences were customized to exploit T1 and T2 contrast mechanisms characteristic of lumpectomy cavities. A three-dimensional image warping algorithm was included to correct for geometric distortions related to nonlinearity of spatially encoding gradients. Respiratory motion, image distortions, and susceptibility artifacts of 3.5-mm titanium surgical clips were examined. Magnetic resonance images of volunteers were acquired repeatedly to analyze residual setup deviations resulting from breast tissue deformation.The customized sequences generated high-resolution magnetic resonance images emphasizing lumpectomy cavity morphology. Respiratory motion was negligible with the subject in the prone position. The gradient-induced nonlinearity was reduced to less than 1 mm in a region 15 cm away from the isocenter of the magnet. Signal-void regions of surgical clips were 4 mm and 8 mm for spin echo and gradient echo images, respectively. Typical residual repositioning errors resulting from breast deformation were estimated to be 3 mm or less.MRI guidance for accelerated partial breast irradiation with the patient in the prone position with adequate contrast, spatial fidelity, and resolution is possible.

    View details for DOI 10.1016/j.ijrobp.2009.03.063

    View details for Web of Science ID 000269328700045

    View details for PubMedID 19632067

  • Recent Advances in MRI of Articular Cartilage AMERICAN JOURNAL OF ROENTGENOLOGY Gold, G. E., Chen, C. A., Koo, S., Hargreaves, B. A., Bangerter, N. K. 2009; 193 (3): 628-638

    Abstract

    MRI is the most accurate noninvasive method available to diagnose disorders of articular cartilage. Conventional 2D and 3D approaches show changes in cartilage morphology. Faster 3D imaging methods with isotropic resolution can be reformatted into arbitrary planes for improved detection and visualization of pathology. Unique contrast mechanisms allow us to probe cartilage physiology and detect changes in cartilage macromolecules.MRI has great promise as a noninvasive comprehensive tool for cartilage evaluation.

    View details for DOI 10.2214/AJR.09.3042

    View details for Web of Science ID 000269305600007

    View details for PubMedID 19696274

    View details for PubMedCentralID PMC2879429

  • Multiecho IDEAL Gradient-Echo Water-Fat Separation for Rapid Assessment of Cartilage Volume at 1.5 T: Initial Experience RADIOLOGY Chen, C. A., Lu, W., John, C. T., Hargreaves, B. A., Reeder, S. B., Delp, S. L., Siston, R. A., Gold, G. E. 2009; 252 (2): 561-567

    Abstract

    Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. The purpose was to prospectively compare multiecho iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) gradient-echo (GRE) magnetic resonance (MR) imaging with three-dimensional fat-suppressed (FS) spoiled GRE (SPGR) MR imaging to evaluate the articular cartilage of the knee. Six healthy volunteer and 10 cadaver knees were imaged at 1.5 T. Signal-to-noise ratio (SNR), SNR efficiency, and cartilage volume were measured. SNR and SNR efficiency were significantly higher with multiecho IDEAL GRE than with FS SPGR imaging (P < .031). Both methods produced equivalent cartilage volumes (overall concordance correlation coefficient, 0.998) with high precision and accuracy. The use of a cartilage phantom confirmed high accuracy in volume measurements and high reproducibility for both methods. Multiecho IDEAL GRE provides high signal intensity in cartilage and synovial fluid and is a promising technique for imaging articular cartilage of the knee.

    View details for DOI 10.1148/radiol.2522081424

    View details for Web of Science ID 000268875900032

    View details for PubMedID 19528355

    View details for PubMedCentralID PMC2753785

  • SEMAC: Slice Encoding for Metal Artifact Correction in MRI 16th Annual Meeting of the International-Society-of-Magnetic-Resonance-in-Medicine Lu, W., Pauly, K. B., Gold, G. E., Pauly, J. M., Hargreaves, B. A. WILEY-BLACKWELL. 2009: 66–76

    Abstract

    Magnetic resonance imaging (MRI) near metallic implants remains an unmet need because of severe artifacts, which mainly stem from large metal-induced field inhomogeneities. This work addresses MRI near metallic implants with an innovative imaging technique called "Slice Encoding for Metal Artifact Correction" (SEMAC). The SEMAC technique corrects metal artifacts via robust encoding of each excited slice against metal-induced field inhomogeneities. The robust slice encoding is achieved by extending a view-angle-tilting (VAT) spin-echo sequence with additional z-phase encoding. Although the VAT compensation gradient suppresses most in-plane distortions, the z-phase encoding fully resolves distorted excitation profiles that cause through-plane distortions. By positioning all spins in a region-of-interest to their actual spatial locations, the through-plane distortions can be corrected by summing up the resolved spins in each voxel. The SEMAC technique does not require additional hardware and can be deployed to the large installed base of whole-body MRI systems. The efficacy of the SEMAC technique in eliminating metal-induced distortions with feasible scan times is validated in phantom and in vivo spine and knee studies.

    View details for DOI 10.1002/mrm.21967

    View details for Web of Science ID 000267404300008

    View details for PubMedID 19267347

    View details for PubMedCentralID PMC2837371

  • Non-contrast-Enhanced Flow-Independent Peripheral MR Angiography with Balanced SSFP MAGNETIC RESONANCE IN MEDICINE Cukur, T., Lee, J. H., Bangerter, N. K., Hargreaves, B. A., Nishimura, D. G. 2009; 61 (6): 1533-1539

    Abstract

    Flow-independent angiography is a non-contrast-enhanced technique that can generate vessel contrast even with reduced blood flow in the lower extremities. A method is presented for producing these angiograms with magnetization-prepared balanced steady-state free precession (bSSFP). Because bSSFP yields bright fat signal, robust fat suppression is essential for detailed depiction of the vasculature. Therefore, several strategies have been investigated to improve the reliability of fat suppression within short scan times. Phase-sensitive SSFP can efficiently suppress fat; however, partial volume effects due to fat and water occupying the same voxel can lead to the loss of blood signal. In contrast, alternating repetition time (ATR) SSFP minimizes this loss; however, the level of suppression is compromised by field inhomogeneity. Finally, a new double-acquisition ATR-SSFP technique reduces this sensitivity to off-resonance. In vivo results indicate that the two ATR-based techniques provide more reliable contrast when partial volume effects are significant.

    View details for DOI 10.1002/mrm.21921

    View details for Web of Science ID 000266429900031

    View details for PubMedID 19365850

    View details for PubMedCentralID PMC2760085

  • Accelerated Bilateral Dynamic Contrast-Enhanced 3D Spiral Breast MRI Using TSENSE JOURNAL OF MAGNETIC RESONANCE IMAGING Han, M., Daniel, B. L., Hargreaves, B. A. 2008; 28 (6): 1425-1434

    Abstract

    To assess the ability of adaptive sensitivity encoding incorporating temporal filtering (TSENSE) to accelerate bilateral dynamic contrast-enhanced (DCE) 3D breast MRI.Bilateral DCE breast magnetic resonance imaging (MRI) exams were performed using a dual-band water-only excitation and a "stack-of-spirals" imaging trajectory. TSENSE was applied in the slab direction with an acceleration factor of 2. Four different techniques for sensitivity map calculation were compared by analyzing resultant contrast uptake curves qualitatively and quantitatively for 10 patient datasets. In addition, image quality and temporal resolution were compared between unaccelerated and TSENSE images.TSENSE can increase temporal resolution by a factor of 2 in DCE imaging, providing better depiction of contrast uptake curves and good image quality. Of the different methods tested, calculation of static sensitivity maps by averaging late postcontrast frames yields the lowest aliasing artifact level based on ROI analysis.TSENSE acceleration combined with 3D spiral imaging is very time-efficient, providing 11-second temporal resolution and 1.1 x 1.1 x 3 mm(3) spatial resolution over a 20 x 20 x 10 cm(3) field of view for each breast.

    View details for DOI 10.1002/jmri.21427

    View details for Web of Science ID 000261270500014

    View details for PubMedID 19025951

  • Water-fat separation with bipolar multiecho sequences MAGNETIC RESONANCE IN MEDICINE Lu, W., Yu, H., Shimakawa, A., Alley, M., Reeder, S. B., Hargreaves, B. A. 2008; 60 (1): 198-209

    Abstract

    Multiecho sequences provide an efficient means to acquire multiple echoes in a single repetition, which has found applications in spectroscopy, relaxometry, and water-fat separation. By replacing the fly-back gradients in unipolar multiecho sequences with alternating readout gradients, bipolar multiecho sequences greatly reduce both echo-spacing and repetition interval. This offers many attractive advantages, such as shorter scan times, higher SNR efficiency, more robust field map estimation, reduced motion-induced artifacts, and less sensitivity to short T(2)*. However, the alternating readout gradients cause several technical problems, including delay effects and image misregistrations, which prevent direct application of existing water-fat separation methods. This work presents solutions to address these problems, including a post-processing method that shifts k-space data to correct k-space echo misalignment, an image warping method that utilizes a low-resolution field map to remove field-inhomogeneity-induced misregistration, and a k-space water-fat separation method that eliminates chemical-shift-induced artifacts in separated water and fat images. In addition, a noise amplification factor, which characterizes the noise present in separated images, is proposed to serve as a useful guideline for choosing imaging parameters or regularization parameters in the case of ill-conditioned separation. The proposed methods are validated both in phantoms and in vivo to enable reliable and SNR efficient water-fat separation with bipolar multiecho sequences.

    View details for DOI 10.1002/mrm.21583

    View details for Web of Science ID 000257267700023

    View details for PubMedID 18581362

  • Pulse sequence for dynamic volumetric imaging of hyperpolarized metabolic products JOURNAL OF MAGNETIC RESONANCE Cunningham, C. H., Chen, A. P., Lustig, M., Hargreaves, B. A., Lupo, J., Xu, D., Kurhanewicz, J., Hurd, R. E., Pauly, J. M., Nelson, S. J., Vigneron, D. B. 2008; 193 (1): 139-146

    Abstract

    Dynamic nuclear polarization and dissolution of a (13)C-labeled substrate enables the dynamic imaging of cellular metabolism. Spectroscopic information is typically acquired, making the acquisition of dynamic volumetric data a challenge. To enable rapid volumetric imaging, a spectral-spatial excitation pulse was designed to excite a single line of the carbon spectrum. With only a single resonance present in the signal, an echo-planar readout trajectory could be used to resolve spatial information, giving full volume coverage of 32 x 32 x 16 voxels every 3.5s. This high frame rate was used to measure the different lactate dynamics in different tissues in a normal rat model and a mouse model of prostate cancer.

    View details for DOI 10.1016/j.jmr.2008.03.012

    View details for Web of Science ID 000256891700019

    View details for PubMedID 18424203

    View details for PubMedCentralID PMC3051833

  • Multiresolution field map estimation using golden section search for water-fat separation MAGNETIC RESONANCE IN MEDICINE Lu, W., Hargreaves, B. A. 2008; 60 (1): 236-244

    Abstract

    Many diagnostic MRI sequences demand reliable and uniform fat suppression. Multipoint water-fat separation methods, which are based on chemical-shift induced phase differences, have shown great success in the presence of field inhomogeneities. This work presents a computationally efficient and robust field map estimation method. The method begins with subsampling image data into a multiresolution image pyramidal structure, and then utilizes a golden section search to directly locate possible field map values at the coarsest level of the pyramidal structure. The field map estimate is refined and propagated to increasingly finer resolutions in an efficient manner until the full-resolution field map is obtained for final water-fat separation. The proposed method is validated with multiecho sequences where long echo-spacings normally impose great challenges on reliable field map estimation.

    View details for DOI 10.1002/mrm.21544

    View details for Web of Science ID 000257267700029

    View details for PubMedID 18581397

  • Wideband SSFP: Alternating repetition time balanced steady state free precession with increased band spacing MAGNETIC RESONANCE IN MEDICINE Nayak, K. S., Lee, H., Hargreaves, B. A., Hu, B. S. 2007; 58 (5): 931-938

    Abstract

    Balanced steady-state free precession (SSFP) imaging is limited by off-resonance banding artifacts, which occur with periodicity 1/TR in the frequency spectrum. A novel balanced SSFP technique for widening the band spacing in the frequency response is described. This method, called wideband SSFP, utilizes two alternating repetition times with alternating RF phase, and maintains high SNR and T(2)/T(1) contrast. For a fixed band spacing, this method can enable improvements in spatial resolution compared to conventional SSFP. Alternatively, for a fixed readout duration this method can widen the band spacing, and potentially avoid the banding artifacts in conventional SSFP. The method is analyzed using simulations and phantom experiments, and is applied to the reduction of banding artifacts in cine cardiac imaging and high-resolution knee imaging at 3T.

    View details for DOI 10.1002/mrm.21296

    View details for Web of Science ID 000250560000010

    View details for PubMedID 17969129

  • Independent phase modulation for efficient dual-band 3D imaging MAGNETIC RESONANCE IN MEDICINE Hargreaves, B. A., Cunningham, C. H., Pauly, J. M., Daniel, B. L. 2007; 57 (4): 798-802

    Abstract

    Certain applications of MRI, such as bilateral breast imaging, require simultaneous imaging of multiple volumes. Although image data can be acquired sequentially, the SNR is often improved if both slabs are excited and imaged together, typically with phase encoding across a volume including both slabs and the space between them. The use of independent phase modulation of multiple slabs eliminates the need to encode empty space between slabs, which can result in a significant time reduction. Each slab is excited with a phase proportional to phase-encode number such that the slab positions in the acquired data are shifted to reduce empty space. With careful consideration this technique is compatible with different pulse sequences (e.g., spin-echo, gradient-echo, RF spoiling, and balanced SSFP (bSSFP)) and acceleration strategies (e.g., partial k-space and parallel imaging). This technique was demonstrated in phantoms and applied to bilateral breast imaging, where scan times were reduced by 20-30%.

    View details for DOI 10.1002/mrm.21180

    View details for Web of Science ID 000245474600019

    View details for PubMedID 17390355

  • Water-fat separation with IDEAL gradient-echo imaging JOURNAL OF MAGNETIC RESONANCE IMAGING Reeder, S. B., McKenzie, C. A., Pineda, A. R., Yu, H., Shimakawa, A., Brau, A. C., Hargreaves, B. A., Gold, G. E., Brittain, J. H. 2007; 25 (3): 644-652

    Abstract

    To combine gradient-echo (GRE) imaging with a multipoint water-fat separation method known as "iterative decomposition of water and fat with echo asymmetry and least squares estimation" (IDEAL) for uniform water-fat separation. Robust fat suppression is necessary for many GRE imaging applications; unfortunately, uniform fat suppression is challenging in the presence of B(0) inhomogeneities. These challenges are addressed with the IDEAL technique.Echo shifts for three-point IDEAL were chosen to optimize noise performance of the water-fat estimation, which is dependent on the relative proportion of water and fat within a voxel. Phantom experiments were performed to validate theoretical SNR predictions. Theoretical echo combinations that maximize noise performance are discussed, and examples of clinical applications at 1.5T and 3.0T are shown.The measured SNR performance validated theoretical predictions and demonstrated improved image quality compared to unoptimized echo combinations. Clinical examples of the liver, breast, heart, knee, and ankle are shown, including the combination of IDEAL with parallel imaging. Excellent water-fat separation was achieved in all cases. The utility of recombining water and fat images into "in-phase," "out-of-phase," and "fat signal fraction" images is also discussed.IDEAL-SPGR provides robust water-fat separation with optimized SNR performance at both 1.5T and 3.0T with multicoil acquisitions and parallel imaging in multiple regions of the body.

    View details for DOI 10.1002/jmri.20831

    View details for Web of Science ID 000244698800025

    View details for PubMedID 17326087

  • Balanced SSFP imaging of the musculoskeletal system JOURNAL OF MAGNETIC RESONANCE IMAGING Gold, G. E., Hargreaves, B. A., Reeder, S. B., Block, W. F., Kijowski, R., Vasanawala, S. S., Kornaat, P. R., Bammer, R., Newbould, R., Bangerter, N. K., Beaulieu, C. F. 2007; 25 (2): 270-278

    Abstract

    Magnetic resonance imaging (MRI), with its unique ability to image and characterize soft tissue noninvasively, has emerged as one of the most accurate imaging methods available to diagnose bone and joint pathology. Currently, most evaluation of musculoskeletal pathology is done with two-dimensional acquisition techniques such as fast spin echo (FSE) imaging. The development of three-dimensional fast imaging methods based on balanced steady-state free precession (SSFP) shows great promise to improve MRI of the musculoskeletal system. These methods may allow acquisition of fluid sensitive isotropic data that can be reformatted into arbitrary planes for improved detection and visualization of pathology. Sensitivity to fluid and fat suppression are important issues in these techniques to improve delineation of cartilage contours, for detection of marrow edema and derangement of other joint structures.

    View details for DOI 10.1002/jmri.20819

    View details for Web of Science ID 000244133000006

    View details for PubMedID 17260387

  • Fluid-attenuated inversion-recovery SSFP imaging JOURNAL OF MAGNETIC RESONANCE IMAGING Bangerter, N. K., Hargreaves, B. A., Gold, G. E., Stucker, D. T., Nishimura, D. G. 2006; 24 (6): 1426-1431

    Abstract

    To describe and evaluate a fast, fluid-suppressed 2D multislice steady-state free precession (SSFP) neuroimaging sequence.We developed a fast fluid-attenuated inversion-recovery SSFP sequence for use in neuroimaging. The inversion time (TI) was optimized to yield good cerebrospinal fluid (CSF) suppression while conserving white matter (WM)/lesion contrast across a broad range of flip angles. Multiple SSFP acquisitions were combined using the sum-of-squares (SOS) method to maximize SNR efficiency while minimizing SSFP banding artifacts. We compared our fluid-attenuated inversion-recovery (FLAIR) SSFP sequence with FLAIR fast spin-echo (FSE) in both normal subjects and a volunteer with multiple sclerosis. SNR measurements were performed to ascertain the SNR efficiency of each sequence.Our FLAIR SSFP sequence demonstrated excellent CSF suppression and good gray matter (GM)/WM contrast. Coverage of the entire brain (5-mm slices, 24-cm FOV, 256 x 192 matrix) was achieved with FLAIR SSFP in less than half the scan time of a corresponding FLAIR FSE sequence with similar SNR, yielding improvements of more than 50% in SNR efficiency. Axial scans of a volunteer with multiple sclerosis show clearly visible plaques and very good visualization of brain parenchyma.We have demonstrated the feasibility of a very fast fluid-suppressed neuroimaging technique using SSFP.

    View details for DOI 10.1002/jmri.20743

    View details for Web of Science ID 000242562000031

    View details for PubMedID 17036358

  • Advanced magnetic resonance imaging of articular cartilage ORTHOPEDIC CLINICS OF NORTH AMERICA Gold, G. E., Hargreaves, B. A., Stevens, K. J., Beaulieu, C. F. 2006; 37 (3): 331-?

    Abstract

    MRI is one of the most accurate imaging methods available to diagnose disorders of articular cartilage. Conventional two-dimensional and three-dimensional approaches show changes in cartilage morphology. Newer and substantially faster three-dimensional imaging methods show great promise to improve MRI of cartilage. These methods may allow acquisition of fluid-sensitive isotropic data that can be reformatted into arbitrary planes for improved detection and visualization of pathology. Unique MRI contrast mechanisms also allow clinicians to probe cartilage physiology and detect early changes in cartilage macromolecules.

    View details for DOI 10.1016/j.ocl.2006.04.006

    View details for Web of Science ID 000239903400007

    View details for PubMedID 16846765

  • Linear combination filtering for T-2-selective imaging of the knee MAGNETIC RESONANCE IN MEDICINE Vidarsson, L., Gold, G. E., Hargreaves, B., Pauly, J. M. 2006; 55 (5): 1191-1196

    Abstract

    Recently a novel T2 selective imaging method based on linear combination (LC) filtering was developed. By linearly combining images acquired with different echo times LC filtering is able to generate images showing only tissues with a preselected range of T2 relaxation times. In this study the use of LC filtering in knee imaging was investigated. Three LC filters were designed: a short LC filter for imaging the knee meniscus, a medium LC filter for articular cartilage, and a long LC filter for synovial fluid. To verify the filter designs, eight phantoms with different T2 relaxation times were imaged. In addition, in vivo images were acquired from four asymptomatic volunteers and a subject with cartilage damage. T2 maps were also generated using the same source images. Signal-to-noise ratio (SNR) measurements were made of the meniscus, cartilage, and fluid regions on the three LC filtered images. The highest SNR was seen in the target tissue on each of the LC filtered images. LC filtering is a new method that can selectively image knee tissues based on their T2.

    View details for DOI 10.1002/mrm.20678

    View details for Web of Science ID 000237151600029

    View details for PubMedID 16586458

  • Respiration-induced B-0 field fluctuation compensation in balanced SSFP: Real-time approach for transition-band SSFP fMRI MAGNETIC RESONANCE IN MEDICINE Lee, J., Santos, J. M., Conolly, S. M., Miller, K. L., Hargreaves, B. A., Pauly, J. M. 2006; 55 (5): 1197-1201

    Abstract

    In functional MRI (fMRI) the resonance frequency shift induced from respiration is a major source of physiological noise. In transition-band SSFP fMRI the respiration-induced resonance offset not only increases noise interference, it also shifts the activation band. This leads to a reduction in the contrast-to-noise ratio (CNR) and the potential for varying contrast levels during the experiment. A novel real-time method that compensates for the respiration-induced resonance offset frequency is presented. This method utilizes free induction decay (FID) phase information to measure the resonance offset. For compensation, one can update the resonant frequency in real time by changing the transmit RF pulse and receiver phases to track the measured offset. The results show decreased signal power in the respiration frequency band and increased numbers of activated voxels with higher Z-scores compared to uncompensated experiments.

    View details for DOI 10.1002/mrm.20879

    View details for Web of Science ID 000237151600030

    View details for PubMedID 16598728

  • Design and analysis of a practical 3D cones trajectory MAGNETIC RESONANCE IN MEDICINE Gurney, P. T., Hargreaves, B. A., Nishimura, D. G. 2006; 55 (3): 575-582

    Abstract

    The 3D Cones k-space trajectory has many desirable properties for rapid and ultra-short echo time magnetic resonance imaging. An algorithm is presented that generates the 3D Cones gradient waveforms given a desired field of view and resolution. The algorithm enables a favorable trade-off between increases in readout time and decreases in the total number of required readouts. The resulting trajectory is very signal-to-noise ratio (SNR) efficient and has excellent aliasing properties. A rapid high-resolution ultra-short echo time imaging sequence is used to compare the 3D Cones trajectory to 3D projection reconstruction (3DPR) sampling schemes. For equivalent scan times, the 3D Cones trajectory has better SNR performance and fewer aliasing artifacts as compared to the 3DPR trajectory.

    View details for DOI 10.1002/mrm.20796

    View details for Web of Science ID 000235858400015

    View details for PubMedID 16450366

  • Dual-acquisition phase-sensitive fat-water separation using balanced steady-state free precession MAGNETIC RESONANCE IMAGING Hargreaves, B. A., Bangerter, N. K., Shimakawa, A., Vasanawala, S. S., Brittain, J. H., Nishimura, D. G. 2006; 24 (2): 113-122

    Abstract

    Balanced steady-state free precession (SSFP) sequences use fully re-focussed gradient waveforms to achieve a high signal and useful image contrast in short scan times. Despite these strengths, the clinical feasibility of balanced SSFP is still limited both by bright fat signal and by the signal voids that result from off-resonance effects such as field or susceptibility variations. A new method, dual-acquisition phase-sensitive SSFP, combines the signals from two standard balanced SSFP acquisitions to separate fat and water while simultaneously reducing the signal voids. The acquisitions are added in quadrature and then phase corrected using a simple algorithm before fat and water can be identified simply by the sign of the signal. This method is especially useful for applications at high field, where the RF power deposition, spatial resolution requirements and gradient strength limit the minimum repetition times. Finally, dual-acquisition phase-sensitive SSFP can be combined with other magnetization preparation schemes to produce specific image contrast in addition to separating fat and water signals.

    View details for DOI 10.1016/j.mri.2005.10.013

    View details for Web of Science ID 000235506400002

    View details for PubMedID 16455400

  • Single breath-hold whole-heart MRA using variable-density spirals at 3T MAGNETIC RESONANCE IN MEDICINE Santos, J. M., Cunningham, C. H., Lustig, M., Hargreaves, B. A., Hu, B. S., Nishimura, D. G., Pauly, J. M. 2006; 55 (2): 371-379

    Abstract

    Multislice breath-held coronary imaging techniques conventionally lack the coverage of free-breathing 3D acquisitions but use a considerably shorter acquisition window during the cardiac cycle. This produces images with significantly less motion artifact but a lower signal-to-noise ratio (SNR). By using the extra SNR available at 3 T and undersampling k-space without introducing significant aliasing artifacts, we were able to acquire high-resolution fat-suppressed images of the whole heart in 17 heartbeats (a single breath-hold). The basic pulse sequence consists of a spectral-spatial excitation followed by a variable-density spiral readout. This is combined with real-time localization and a real-time prospective shim correction. Images are reconstructed with the use of gridding, and advanced techniques are used to reduce aliasing artifacts.

    View details for DOI 10.1002/mrm.20765

    View details for Web of Science ID 000235326500019

    View details for PubMedID 16408262

  • Articular cartilage of the knee: Evaluation with fluctuating equilibrium MR imaging - Initial experience in healthy volunteers RADIOLOGY Gold, G. E., Hargreaves, B. A., Vasanawala, S. S., Webb, J. D., Shimakawa, A. S., Brittain, J. H., Beaulieu, C. F. 2006; 238 (2): 712-718

    Abstract

    Institutional review board approval and informed consent were obtained for this HIPAA-compliant study, whose purpose was to prospectively compare three magnetic resonance (MR) imaging techniques-fluctuating equilibrium, three-dimensional (3D) spoiled gradient-recalled acquisition in the steady state (SPGR), and two-dimensional (2D) fast spin echo (SE)-for evaluating articular cartilage in the knee. The study cohort consisted of 10 healthy volunteers (four men, six women; age range, 26-42 years). Cartilage signal-to-noise ratio (SNR), SNR efficiency, cartilage-fluid contrast-to-noise ratio (CNR), CNR efficiency, image quality, cartilage visibility, and fat suppression were compared. Cartilage volume was compared for the fluctuating equilibrium and 3D SPGR techniques. Compared with 3D SPGR and 2D fast SE, fluctuating equilibrium yielded the highest cartilage SNR efficiency and cartilage-fluid CNR efficiency (P < .01 for both). Image quality was similar with all sequences. Fluctuating equilibrium imaging yielded higher cartilage visibility than did 2D fast SE imaging (P <. 01) but worse fat suppression than did 3D SPGR and 2D fast SE imaging (P < .04). Cartilage volume measurements with fluctuating equilibrium and 3D SPGR were similar. Fluctuating equilibrium MR imaging is a promising method for evaluating articular cartilage in the knee.

    View details for DOI 10.1148/radiol.2381042183

    View details for Web of Science ID 000234859100040

    View details for PubMedID 16436826

  • Automatic tuning of flexible interventional RF receiver coils MAGNETIC RESONANCE IN MEDICINE Venook, R. D., Hargreaves, B. A., Gold, G. E., Conolly, S. M., Scott, G. C. 2005; 54 (4): 983-993

    Abstract

    Microcontroller-based circuitry was built and tested for automatically tuning flexible RF receiver coils at the touch of a button. This circuitry is robust to 10% changes in probe center frequency, is in line with the scanner, and requires less than 1 s to tune a simple probe. Images were acquired using this circuitry with a varactor-tunable 1-inch flexible probe in a phantom and in an in vitro porcine knee model. The phantom experiments support the use of automatic tuning by demonstrating 30% signal-to-noise ratio (SNR) losses for 5% changes in coil center frequency, in agreement with theoretical calculations. Comparisons between patellofemoral cartilage images obtained using a 3-inch surface coil and the surgically-implanted 1-inch flexible coil reveal a worst-case local SNR advantage of a factor of 4 for the smaller coil. This work confirms that surgically implanted coils can greatly improve resolution in small-field-of-view (FOV) applications, and demonstrates the importance and feasibility of automatically tuning such probes.

    View details for DOI 10.1002/mrm.20616

    View details for Web of Science ID 000232348000027

    View details for PubMedID 16155871

  • Variable-density one-shot Fourier velocity encoding MAGNETIC RESONANCE IN MEDICINE DiCarlo, J. C., Hargreaves, B. A., Nayak, K. S., Hu, B. S., Pauly, J. M., Nishimura, D. G. 2005; 54 (3): 645-655

    Abstract

    In areas of highly pulsatile and turbulent flow, real-time imaging with high temporal, spatial, and velocity resolution is essential. The use of 1D Fourier velocity encoding (FVE) was previously demonstrated for velocity measurement in real time, with fewer effects resulting from off-resonance. The application of variable-density sampling is proposed to improve velocity measurement without a significant increase in readout time or the addition of aliasing artifacts. Two sequence comparisons are presented to improve velocity resolution or increase the velocity field of view (FOV) to unambiguously measure velocities up to 5 m/s without aliasing. The results from a tube flow phantom, a stenosis phantom, and healthy volunteers are presented, along with a comparison of measurements using Doppler ultrasound (US). The studies confirm that variable-density acquisition of kz-kv space improves the velocity resolution and FOV of such data, with the greatest impact on the improvement of FOV to include velocities in stenotic ranges.

    View details for DOI 10.1002/mrm.20594

    View details for Web of Science ID 000231494000016

    View details for PubMedID 16088883

  • Controversies in protocol selection in the Imaging of articular cartilage SEMINARS IN MUSCULOSKELETAL RADIOLOGY Gold, G. E., Hargreaves, B. A., Reeder, S. B., Vasanawala, S. S., Beaulieu, C. F. 2005; 9 (2): 161-172

    Abstract

    Magnetic resonance (MR) imaging, with its unique ability to noninvasively image and characterize soft tissue, has shown promise in assessment of cartilage. The development of new, fast imaging methods with high contrast will improve the MR evaluation of cartilage morphology. In addition to morphological MR imaging methods, MR imaging contrast mechanisms under development may reveal detailed information regarding the physiology of cartilage. However, many of these methods remain to be tested in the clinical setting. Protocol selection for cartilage imaging requires understanding of the patient population and the advantages and limitations of these techniques.

    View details for Web of Science ID 000230039200008

    View details for PubMedID 16044384

  • Spiral balanced steady-state free precession cardiac imaging MAGNETIC RESONANCE IN MEDICINE Nayak, K. S., Hargreaves, B. A., Hu, B. S., Nishimura, D. G., Pauly, J. M., Meyer, C. H. 2005; 53 (6): 1468-1473

    Abstract

    Balanced steady-state free precession (SSFP) sequences are useful in cardiac imaging because they achieve high signal efficiency and excellent blood-myocardium contrast. Spiral imaging enables the efficient acquisition of cardiac images with reduced flow and motion artifacts. Balanced SSFP has been combined with spiral imaging for real-time interactive cardiac MRI. New features of this method to enable scanning in a clinical setting include short, first-moment nulled spiral trajectories and interactive control over the spatial location of banding artifacts (SSFP-specific signal variations). The feasibility of spiral balanced SSFP cardiac imaging at 1.5 T is demonstrated. In observations from over 40 volunteer and patient studies, spiral balanced SSFP imaging shows significantly improved contrast compared to spiral gradient-spoiled imaging, producing better visualization of cardiac function, improved localization, and reduced flow artifacts from blood.

    View details for DOI 10.1002/mrm.20489

    View details for Web of Science ID 000229468200031

    View details for PubMedID 15906302

  • Rapid musculoskeletal MRI with phase-sensitive steady-state free precession: Comparison with routine knee MRI AMERICAN JOURNAL OF ROENTGENOLOGY Vasanawala, S. S., Hargreaves, B. A., Pauly, J. M., Nishimura, D. G., Beaulieu, C. F., Gold, G. E. 2005; 184 (5): 1450-1455

    Abstract

    The aim of this work was to show the potential utility of a novel rapid 3D fat-suppressed MRI method for joint imaging.Phase-sensitive steady-state free precession provides rapid 3D joint imaging with robust fat suppression and excellent cartilage delineation.

    View details for Web of Science ID 000228875300013

    View details for PubMedID 15855095

  • Rapid measurement of renal artery blood flow with ungated spiral phase-contrast MRI 10th Annual Meeting of the International-Society-for-Magnetic-Resonance-in-Medicine (ISMRM) Park, J. B., Santos, J. M., Hargreaves, B. A., Nayak, K. S., Sommer, G., Hu, B. S., Nishimura, D. G. JOHN WILEY & SONS INC. 2005: 590–95

    Abstract

    To verify the potential of ungated spiral phase-contrast (USPC), which has been shown to provide accurate and reproducible time-averaged measurements of pulsatile flow, for rapid measurement of renal artery blood flow (RABF) in vivo.The RABF rates of 11 normal human subjects and one patient with renal failure were measured with USPC within six seconds.Rapid USPC scans produced reproducible RABF measurements (SD < or = 9%) that agreed with the normal RABF rates known from the literature. The RABF rates of the patient with renal failure were substantially less (<50-65%) than the normal RABF rates.The results demonstrate that it is now possible to obtain rapid and consistent RABF measurements within six seconds with USPC.

    View details for DOI 10.1002/jmri.20325

    View details for Web of Science ID 000228653600012

    View details for PubMedID 15834919

  • Driven equilibrium magnetic resonance imaging of articular cartilage: Initial clinical experience JOURNAL OF MAGNETIC RESONANCE IMAGING Gold, G. E., Fuller, S. E., Hargreaves, B. A., Stevens, K. J., Beaulieu, C. F. 2005; 21 (4): 476-481

    Abstract

    To evaluate three-dimensional driven equilibrium Fourier transform (3D-DEFT) for image quality and detection of articular cartilage lesions in the knee.We imaged 104 consecutive patients with knee pain with 3D-DEFT and proton density (PD-FSE) and T2-weighted (T2-FSE) fast spin echo. Twenty-four went on to arthroscopy. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) efficiency were measured. Subjective image quality, fat suppression, and cartilage thickness visibility were assessed. Cartilage lesions on 3D-DEFT and T2-FSE were compared with findings outlined in operative reports.SNR efficiency was higher for 3D-DEFT and PD-FSE than for T2-FSE (P < 0.02). 3D-DEFT and PD-FSE showed superior cartilage thickness visibility compared with T2-FSE (P < 0.02). T2-FSE showed better fat suppression and fewer image artifacts than 3D-DEFT (P < 0.04). 3D-DEFT had similar sensitivity and similar specificity for cartilage lesions compared with PD-FSE and T2-FSE.3D-DEFT provides excellent synovial fluid-to-cartilage contrast while preserving signal from cartilage, giving this method a high cartilage SNR. 3D-DEFT shows the full cartilage thickness better than T2-FSE. T2-FSE had superior fat saturation and fewer artifacts than 3D-DEFT. Overall, 3D-DEFT requires further technical development, but is a promising method for imaging articular cartilage.

    View details for DOI 10.1002/jhmi.20276

    View details for Web of Science ID 000228029900022

    View details for PubMedID 15779031

  • Magnetic resonance imaging of articular cartilage of the knee: Comparison between fat-suppressed three-dimensional SPGR imaging, fat-suppressed FSE imaging, and fat-suppressed three-dimensional DEFT imaging, and correlation with arthroscopy JOURNAL OF MAGNETIC RESONANCE IMAGING Yoshioka, H., Stevens, K., Hargreaves, B. A., Steines, D., Genovese, M., Dillingham, M. F., Winalski, C. S., Lang, P. 2004; 20 (5): 857-864

    Abstract

    To compare signal-to-noise ratios (S/N) and contrast-to-noise ratios (C/N) in various MR sequences, including fat-suppressed three-dimensional spoiled gradient-echo (SPGR) imaging, fat-suppressed fast spin echo (FSE) imaging, and fat-suppressed three-dimensional driven equilibrium Fourier transform (DEFT) imaging, and to determine the diagnostic accuracy of these imaging sequences for detecting cartilage lesions in osteoarthritic knees, as compared with arthroscopy.Two sagittal fat-suppressed FSE images (repetition time [TR] / echo time [TE], 4000/13 [FSE short TE] and 4000/39 [FSE long TE]), sagittal fat-suppressed three-dimensional SPGR images (60/5, 40 degrees flip angle), and sagittal fat-suppressed echo-planar three-dimensional DEFT images (400/21.2) were acquired in 35 knees from 28 patients with osteoarthritis of the knee. The S/N efficiencies (S/Neffs) of cartilage, synovial fluid, muscle, meniscus, bone marrow, and fat tissue, and the C/N efficiencies (C/Neffs) of these structures were calculated. Kappa values, exact agreement, sensitivity, specificity, positive predictive value, and negative predictive value were determined by comparison of MR grading with arthroscopic results.The synovial fluid S/Neff on fat-suppressed FSE short TE images, fat-suppressed FSE long TE images, and fat-suppressed three-dimensional DEFT images showed similar values. Fat-suppressed three-dimensional DEFT images showed the highest fluid-cartilage C/Neff of all sequences. All images showed fair to good agreement with arthroscopy (kappa, 0.615 in FSE short TE, 0.601 in FSE long TE, 0.583 in three-dimensional SPGR, and 0.561 in three-dimensional DEFT). Although the sensitivity of all sequences was high (100% in FSE short TE, FSE long TE, and DEFT; 96.7% in SPGR), specificity was relatively low (67.6% in FSE short TE and FSE long TE; 85.3% in SPGR; 58.3% in DEFT). The peripheral area of bone marrow edema or whole area of bone marrow edema on fat-suppressed FSE images was demonstrated as low or iso-signal intensity on fat-suppressed three-dimensional DEFT images.Fat-suppressed three-dimensional SPGR imaging and fat-suppressed FSE imaging showed high sensitivity and high negative predictive values, but relatively low specificity. The Kappa value and exact agreement was the highest on fat-suppressed FSE short TE images. Fat-suppressed three-dimensional DEFT images showed results similar to the conventional sequences.

    View details for DOI 10.1002/jmri.20193

    View details for Web of Science ID 000224762700017

    View details for PubMedID 15503323

  • Variable-rate selective excitation for rapid MRI sequences MAGNETIC RESONANCE IN MEDICINE Hargreaves, B. A., Cunningham, C. H., Nishimura, D. G., Conolly, S. M. 2004; 52 (3): 590-597

    Abstract

    Balanced steady-state free precession (SSFP) imaging sequences require short repetition times (TRs) to avoid off-resonance artifacts. The use of slab-selective excitations is common, as this can improve imaging speed by limiting the field of view (FOV). However, the necessarily short-duration excitations have poor slab profiles. This results in unusable slices at the slab edge due to significant flip-angle variations or aliasing in the slab direction. Variable-rate selective excitation (VERSE) is a technique by which a time-varying gradient waveform is combined with a modified RF waveform to provide the same excitation profile with different RF power and duration characteristics. With the use of VERSE, it is possible to design short-duration pulses with dramatically improved slab profiles. These pulses achieve high flip angles with only minor off-resonance sensitivity, while meeting SAR limits at 1.5 T. The improved slab profiles will enable more rapid 3D imaging of limited volumes, with more consistent image contrast across the excited slab.

    View details for DOI 10.1002/mrm.20168

    View details for Web of Science ID 000223529200020

    View details for PubMedID 15334579

  • Analysis of multiple-acquisition SSFP MAGNETIC RESONANCE IN MEDICINE Bangerter, N. K., Hargreaves, B. A., Vasanawala, S. S., Pauly, J. M., Gold, G. E., Nishimura, D. G. 2004; 51 (5): 1038-1047

    Abstract

    Refocused steady-state free precession (SSFP) is limited by its high sensitivity to local field variation, particularly at high field strengths or the long repetition times (TRs) necessary for high resolution. Several methods have been proposed to reduce SSFP banding artifact by combining multiple phase-cycled SSFP acquisitions, each differing in how individual signal magnitudes and phases are combined. These include maximum-intensity SSFP (MI-SSFP) and complex-sum SSFP (CS-SSFP). The reduction in SSFP banding is accompanied by a loss in signal-to-noise ratio (SNR) efficiency. In this work a general framework for analyzing banding artifact reduction, contrast, and SNR of any multiple-acquisition SSFP combination method is presented. A new sum-of-squares method is proposed, and a comparison is performed between each of the combination schemes. The sum-of-squares SSFP technique (SOS-SSFP) delivers both robust banding artifact reduction and higher SNR efficiency than other multiple-acquisition techniques, while preserving SSFP contrast.

    View details for DOI 10.1002/mrm.20052

    View details for Web of Science ID 000221239000022

    View details for PubMedID 15122688

  • Steady-state diffusion-weighted imaging of in vivo knee cartilage MAGNETIC RESONANCE IN MEDICINE Miller, K. L., Hargreaves, B. A., Gold, G. E., Pauly, J. M. 2004; 51 (2): 394-398

    Abstract

    Diffusion-weighted imaging (DWI) has strong potential as a diagnostic for early cartilage damage, with clinical impact for diseases such as osteoarthritis. However, in vivo DWI of cartilage has proven difficult with conventional methods due to the short T2. This work presents a 3D steady-state DWI sequence that is able to image short-T2 species with high SNR. When combined with 2D navigator correction of motion-induced phase artifacts, this method enables high resolution in vivo DWI of cartilage. In vivo knee images in healthy subjects are presented with high SNR (SNR = 110) and submillimeter in-plane resolution (0.5 x 0.7 x 3.0 mm(3)). A method for fitting the diffusion coefficient is presented which produces fits within 10% of literature values. This method should be applicable to other short-T2 tissues, such as muscle, which are difficult to image using traditional DWI methods.

    View details for DOI 10.1002/mrm.10696

    View details for Web of Science ID 000188718600023

    View details for PubMedID 14755666

  • Functional brain imaging with BOSSFMRI 26th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society Miller, K. L., Hargreaves, B. A., Lee, J. H., Ress, D., deCharms, R. C., Pauly, J. M. IEEE. 2004: 5234–5237

    View details for Web of Science ID 000225461801389

  • Functional brain imaging with BOSS FMRI. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference Miller, K. L., Hargreaves, B. A., Lee, J., Ress, D., deCharms, R. C., Pauly, J. M. 2004; 7: 5234-5237

    Abstract

    The standard method for FMRI, using the blood oxygenation level dependent (BOLD) effect, has significant limitations that result from the coupling of functional contrast to sources of image artifact. We have developed an alternative method for FMRI based on balanced-SSFP imaging. This method uses the balanced-SSFP phase profile to invert the signal in deoxygenated blood relative to oxygenated blood. The resulting blood oxygenation sensitive steady-state (BOSS) signal decouples functional contrast from imaging, enabling significantly better image quality than BOLD FMRI. BOSS FMRI is very SNR-efficient, achieves strong functional contrast and is relatively immune to susceptibility gradients. In this paper, we present results validating the ability to detect functional activity using BOSS FMRI. One of the potential advantages of BOSS FMRI is the ability to acquire high-resolution data due to the SNR efficiency of balanced-SSFP. Preliminary high resolution results (1 x 1 x 2 mm/sup 3/) at 1.5 T are presented.

    View details for PubMedID 17271520

  • Time-optimal multidimensional gradient waveform design for rapid imaging MAGNETIC RESONANCE IN MEDICINE Hargreaves, B. A., Nishimura, D. G., Conolly, S. M. 2004; 51 (1): 81-92

    Abstract

    Magnetic resonance imaging (MRI) is limited in many cases by long scan times and low spatial resolution. Recent advances in gradient systems hardware allow very rapid imaging sequences, such as steady-state free precession (SSFP), which has repetition times (TRs) of 2-5 ms. The design of these rapid sequences demands time-optimal preparatory gradient waveforms to provide maximum readout duty-cycle, and preserve spatial resolution and SNR while keeping TRs low. Time-optimal gradient waveforms can be synthesized analytically for certain simple cases. However, certain problems, such as time-optimal 2D and 3D gradient design with moment constraints, either may not have a solution or must be solved numerically. We show that time-optimal gradient design is a convex-optimization problem, for which very efficient solution methods exist. These methods can be applied to solve gradient design problems for oblique gradient design, spiral imaging, and flow-encoding using either a constant slew rate or the more exact voltage-limited gradient models. Ultimately, these methods provide a time-optimal solution to many 2D and 3D gradient design problems in a sufficiently short time for interactive imaging.

    View details for Web of Science ID 000188041500012

    View details for PubMedID 14705048

  • Fast 3D imaging using variable-density spiral trajectories with applications to limb perfusion MAGNETIC RESONANCE IN MEDICINE Lee, J. H., Hargreaves, B. A., Hu, B. S., Nishimura, D. G. 2003; 50 (6): 1276-1285

    Abstract

    Variable-density k-space sampling using a stack-of-spirals trajectory is proposed for ultra fast 3D imaging. Since most of the energy of an image is concentrated near the k-space origin, a variable-density k-space sampling method can be used to reduce the sampling density in the outer portion of k-space. This significantly reduces scan time while introducing only minor aliasing artifacts from the low-energy, high-spatial-frequency components. A stack-of-spirals trajectory allows control over the density variations in both the k(x)-k(y) plane and the k(z) direction while fast k-space coverage is provided by spiral trajectories in the k(x)-k(y) plane. A variable-density stack-of-spirals trajectory consists of variable-density spirals in each k(x)-k(y) plane that are located in varying density in the k(z) direction. Phantom experiments demonstrate that reasonable image quality is preserved with approximately half the scan time. This technique was then applied to first-pass perfusion imaging of the lower extremities which demands very rapid volume coverage. Using a variable-density stack-of-spirals trajectory, 3D images were acquired at a temporal resolution of 2.8 sec over a large volume with a 2.5 x 2.5 x 8 mm(3) spatial resolution. These images were used to resolve the time-course of muscle intensity following contrast injection.

    View details for DOI 10.1002/mrm.10644

    View details for Web of Science ID 000186991500019

    View details for PubMedID 14648576

  • Helical MR: Continuously moving table axial imaging with radial acquisitions MAGNETIC RESONANCE IN MEDICINE Shankaranarayanan, A., Herfkens, R., Hargreaves, B. M., Polzin, J. A., Santos, J. M., Brittain, J. H. 2003; 50 (5): 1053-1060

    Abstract

    A technique for extended field of view MRI is presented. Similar to helical computed tomography, the method utilizes a continuously moving patient table, a 2D axial slice that remains fixed relative to the MRI magnet, and a radial k-space trajectory. A fully refocused SSFP acquisition enables spatial resolution comparable to current clinical protocols in scan times that are sufficiently short to allow a reasonable breathhold duration. RF transmission and signal reception are performed using the RF body coil and the images are reconstructed in real time. Experimental results are presented that illustrate the technique's ability to resolve small structures in the table-motion direction. Simulation experiments to study the steady-state response of the fully refocused SSFP acquisition during continuous table motion are also presented. Finally, whole body images of healthy volunteers demonstrate the high image quality achieved using the helical MRI approach.

    View details for DOI 10.1002/mrm.10621

    View details for Web of Science ID 000186326400019

    View details for PubMedID 14587016

  • Functional brain Imaging using a blood oxygenation sensitive steady state MAGNETIC RESONANCE IN MEDICINE Miller, K. L., Hargreaves, B. A., Lee, J., Ress, D., deCharms, R. C., Pauly, J. M. 2003; 50 (4): 675-683

    Abstract

    Blood oxygenation level dependent (BOLD) functional MRI (fMRI) is an important method for functional neuroimaging that is sensitive to changes in blood oxygenation related to brain activation. While BOLD imaging has good spatial coverage and resolution relative to other neuroimaging methods (such as positron emission tomography (PET)), it has significant limitations relative to other MRI techniques, including poor spatial resolution, low signal levels, limited contrast, and image artifacts. These limitations derive from the coupling of BOLD functional contrast to sources of image degradation. This work presents an alternative method for fMRI that may over-come these limitations by establishing a blood oxygenation sensitive steady-state (BOSS) that inverts the signal from deoxygenated blood relative to the water signal. BOSS fMRI allows the imaging parameters to be optimized independently of the functional contrast, resulting in fewer image artifacts and higher signal-to-noise ratio (SNR). In addition, BOSS fMRI has greater functional contrast than BOLD. BOSS fMRI requires careful shimming and multiple acquisitions to obtain a precise alignment of the magnetization to the SSFP frequency response.

    View details for DOI 10.1002/mrm.10602

    View details for Web of Science ID 000185698000004

    View details for PubMedID 14523951

  • Fat-suppressed steady-state free precession imaging using phase detection MAGNETIC RESONANCE IN MEDICINE Hargreaves, B. A., Vasanawala, S. S., Nayak, K. S., Hu, B. S., Nishimura, D. G. 2003; 50 (1): 210-213

    Abstract

    Fully refocused steady-state free precession (SSFP) is a rapid, efficient imaging sequence that can provide diagnostically useful image contrast. In SSFP, the signal is refocused midway between excitation pulses, much like in a spin-echo experiment. However, in SSFP, the phase of the refocused spins alternates for each resonant frequency interval equal to the reciprocal of the sequence repetition time (TR). Appropriate selection of the TR results in a 180 degrees phase difference between lipid and water signals. This phase difference can be used for fat-water separation in SSFP without any increase in scan time. The technique is shown to produce excellent non-contrast-enhanced, flow-independent angiograms of the peripheral vasculature.

    View details for DOI 10.1002/mrm.10488

    View details for Web of Science ID 000183961800028

    View details for PubMedID 12815698

  • Comparison of new sequences for high-resolution cartilage imaging MAGNETIC RESONANCE IN MEDICINE Hargreaves, B. A., Gold, G. E., Beaulieu, C. F., Vasanawala, S. S., Nishimura, D. G., Pauly, J. M. 2003; 49 (4): 700-709

    Abstract

    The high prevalence of osteoarthritis continues to demand improved accuracy in detecting cartilage injury and monitoring its response to different treatments. MRI is the most accurate noninvasive method of diagnosing cartilage lesions. However, MR imaging of cartilage is limited by scan time, signal-to-noise ratio (SNR), and image contrast. Recently, there has been renewed interest in SNR-efficient imaging sequences for imaging cartilage, including various forms of steady-state free-precession as well as driven-equilibrium imaging. This work compares several of these sequences with existing methods, both theoretically and in normal volunteers. Results show that the new steady-state methods increase SNR-efficiency by as much as 30% and improve cartilage-synovial fluid contrast by a factor of three. Additionally, these methods markedly decrease minimum scan times, while providing 3D coverage without the characteristic blurring seen in fast spin-echo images.

    View details for DOI 10.1002/mrm.10424

    View details for Web of Science ID 000182007200013

    View details for PubMedID 12652541

  • Protocols in sports magnetic resonance imaging. Topics in magnetic resonance imaging Gold, G. E., Hargreaves, B. A., Beaulieu, C. F. 2003; 14 (1): 3-23

    Abstract

    Magnetic resonance imaging, with its multiplanar imaging capability and superior soft-tissue contrast, has become the preferred method for imaging sports-related injuries. Advances in gradient technology, receiver coils, and imaging software have allowed the imaging of the injured athlete to take place quickly and at high resolution. Understanding the tissues being imaged, the underlying anatomy, and the capabilities of today's scanners is crucial to the design of intelligent and efficient protocols.

    View details for PubMedID 12606866

  • Characterization and reduction of the transient response in steady-state MR imaging MAGNETIC RESONANCE IN MEDICINE Hargreaves, B. A., Vasanawala, S. S., Pauly, J. M., Nishimura, D. G. 2001; 46 (1): 149-158

    Abstract

    Refocused steady-state free precession (SSFP) imaging sequences have recently regained popularity as faster gradient hardware has allowed shorter repetition times, thereby reducing SSFP's sensitivity to off-resonance effects. Although these sequences offer fast scanning with good signal-to-noise efficiency, the "transient response," or time taken to reach a steady-state, can be long compared with the total imaging time, particularly when using 2D sequences. This results in lost imaging time and has made SSFP difficult to use for real-time and cardiac-gated applications. A linear-systems analysis of the steady-state and transient response for general periodic sequences is shown. The analysis is applied to refocused-SSFP sequences to generate a two-stage method of "catalyzing," or speeding up the progression to steady-state by first scaling, then directing the magnetization. This catalyzing method is compared with previous methods in simulations and experimentally. Although the second stage of the method exhibits some sensitivity to B(1) variations, our results show that the transient time can be significantly reduced, allowing imaging in a shorter total scan time. Magn Reson Med 46:149-158, 2001.

    View details for Web of Science ID 000169561000019

    View details for PubMedID 11443721

  • MR imaging of articular cartilage using driven equilibrium Scientific Meeting of the International-Society-for-Magnetic-Resonance-in-Medicine Hargreaves, B. A., Gold, G. E., Lang, P. K., Conolly, S. M., Pauly, J. M., Bergman, G., Vandevenne, J., Nishimura, D. G. JOHN WILEY & SONS INC. 1999: 695–703

    Abstract

    The high incidence of osteoarthritis and the recent advent of several new surgical and non-surgical treatment approaches have motivated the development of quantitative techniques to assess cartilage loss. Although magnetic resonance (MR) imaging is the most accurate non-invasive diagnostic modality for evaluating articular cartilage, improvements in spatial resolution, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) would be valuable. Cartilage presents an imaging challenge due to its short T(2) relaxation time and its low water content compared with surrounding materials. Current methods sacrifice cartilage signal brightness for contrast between cartilage and surrounding tissue such as bone, bone marrow, and joint fluid. A new technique for imaging articular cartilage uses driven equilibrium Fourier transform (DEFT), a method of enhancing signal strength without waiting for full T(1) recovery. Compared with other methods, DEFT imaging provides a good combination of bright cartilage and high contrast between cartilage and surrounding tissue. Both theoretical predictions and images show that DEFT is a valuable method for imaging articular cartilage when compared with spoiled gradient-recalled acquisition in the steady state (SPGR) or fast spin echo (FSE). The cartilage SNR for DEFT is as high as that of either FSE or SPGR, while the cartilage-synovial fluid CNR of DEFT is as much as four times greater than that of FSE or SPGR. Implemented as a three-dimensional sequence, DEFT can achieve coverage comparable to that of other sequences in a similar scan time. Magn Reson Med 42:695-703, 1999.

    View details for Web of Science ID 000082944400011

    View details for PubMedID 10502758

  • Magnetic resonance imaging of knee cartilage repair. Topics in magnetic resonance imaging Gold, G. E., Bergman, A. G., Pauly, J. M., Lang, P., Butts, R. K., Beaulieu, C. F., Hargreaves, B., Frank, L., Boutin, R. D., Macovski, A., Resnick, D. 1998; 9 (6): 377-392

    Abstract

    Cartilage injury resulting in osteoarthritis is a frequent cause of disability in young people. Osteoarthritis, based on either cartilage injury or degeneration, is a leading cause of disability in the United States. Over the last several decades, much progress has been made in understanding cartilage injury and repair. Magnetic resonance (MR) imaging, with its unique ability to noninvasively image and characterize soft tissue, has shown promise in assessment of cartilage integrity. In addition to standard MR imaging methods, MR imaging contrast mechanisms under development may reveal detailed information regarding the physiology and morphology of cartilage. MR imaging will play a crucial role in assessing the success or failure of therapies for cartilage injury and degeneration.

    View details for PubMedID 9894740