Incidence of Nephrogenic Systemic Fibrosis Using Gadobenate Dimeglumine in 1423 Patients With Renal Insufficiency Compared With Gadodiamide.
2016; 51 (11): 701-705
Muscle velocity and inertial force from phase contrast MRI
JOURNAL OF MAGNETIC RESONANCE IMAGING
2015; 42 (2): 526-532
The purpose of this study was to assess the incidence of nephrogenic systemic fibrosis (NSF) before and after educational interventions, implementation of a clinical screening process, and change to gadobenate dimeglumine in patients who had an estimated glomerular filtration rate (eGFR) of 30 mL/min per 1.72 m or less.This is a Health Insurance Portability and Accountability Act compliant, institutional review board exempt study. Two periods were studied-July 2005 to June 2006, during which gadodiamide was utilized as our magnetic resonance (MR) contrast agent, and November 2006 to August 2014, during which gadobenate dimeglumine was used as our MR contrast agent in patients who had an eGFR 30 mL/min per 1.72 m or less. In addition to a change in the MR contrast agent, education of our staff physician to the risks of NSF with MR contrast agents and the implementation of a clinical screening process occurred. The rate of NSF before and after the interventions was compared using the ? test.There was a statistically significant difference in the incidence of NSF in patients with an eGFR 30 mL/min per 1.72 m or less between the 2 periods: July 2005 to June 2006, 6 of 246 patients were diagnosed with NSF (P < 0.001), versus November 2006 to August 2014, 0 of 1423 patients were diagnosed with NSF.Our data demonstrates a marked decrease in the incidence of NSF after education of our referring physicians, implementation of clinical screening process, and change to gadobenate dimeglumine from gadodiamide in patients with renal insufficiency. This approach potentially provides an acceptable risk-benefit profile for patients with renal insufficiency that required MR imaging for clinical care.
View details for PubMedID 26885631
Measurements of Wall Shear Stress and Aortic Pulse Wave Velocity in Swine With Familial Hypercholesterolemia
JOURNAL OF MAGNETIC RESONANCE IMAGING
2015; 41 (5): 1475-1485
To evaluate velocity waveforms in muscle and to create a tool and algorithm for computing and analyzing muscle inertial forces derived from 2D phase contrast (PC) magnetic resonance imaging (MRI).PC MRI was performed in the forearm of four healthy volunteers during 1 Hz cycles of wrist flexion-extension as well as in the lower leg of six healthy volunteers during 1 Hz cycles of plantarflexion-dorsiflexion. Inertial forces (F) were derived via the equation F?=?ma. The mass, m, was derived by multiplying voxel volume by voxel-by-voxel estimates of density via fat-water separation techniques. Acceleration, a, was obtained via the derivative of the PC MRI velocity waveform.Mean velocities in the flexors of the forearm and lower leg were 1.94?±?0.97 cm/s and 5.57?±?2.72 cm/s, respectively, as averaged across all subjects; the inertial forces in the flexors of the forearm and lower leg were 1.9 × 10(-3) ?±?1.3 × 10(-3) N and 1.1 × 10(-2) ?±?6.1 × 10(-3) N, respectively, as averaged across all subjects.PC MRI provided a promising means of computing muscle velocities and inertial forces-providing the first method for quantifying inertial forces. J. Magn. Reson. Imaging 2015;42:526-532.
View details for DOI 10.1002/jmri.24807
View details for Web of Science ID 000358258600001
View details for PubMedCentralID PMC4442766
Simultaneous MRI of Lung Structure and Perfusion in a Single Breathhold
JOURNAL OF MAGNETIC RESONANCE IMAGING
2015; 41 (1): 52-59
To assess measurements of pulse wave velocity (PWV) and wall shear stress (WSS) in a swine model of atherosclerosis.Nine familial hypercholesterolemic (FH) swine with angioplasty balloon catheter-induced atherosclerotic lesions to the abdominal aorta (injured group) and 10 uninjured FH swine were evaluated with a 4D phase contrast (PC) magnetic resonance imaging (MRI) acquisition, as well as with radial and Cartesian 2D PC acquisitions, on a 3T MR scanner. PWV values were computed from the 2D and 4D PC techniques, compared between the injured and uninjured swine, and validated against reference standard pressure probe-based PWV measurements. WSS values were also computed from the 4D PC MRI technique and compared between injured and uninjured groups.PWV values were significantly greater in the injured than in the uninjured groups with the 4D PC MRI technique (P?=?0.03) and pressure probes (P?=?0.02). No significant differences were found in PWV between groups using the 2D PC techniques (P?=?0.75-0.83). No significant differences were found for WSS values between the injured and uninjured groups.The 4D PC MRI technique provides a promising means of evaluating PWV and WSS in a swine model of atherosclerosis, providing a potential platform for developing the technique for the early detection of atherosclerosis.
View details for DOI 10.1002/jmri.24681
View details for Web of Science ID 000353641600036
View details for PubMedID 24964097
Review of MRI-based measurements of pulse wave velocity: a biomarker of arterial stiffness.
Cardiovascular diagnosis and therapy
2014; 4 (2): 193-206
To develop and demonstrate a breathheld 3D radial ultrashort echo time (UTE) acquisition to visualize co-registered lung perfusion and vascular structure.Nine healthy dogs were scanned twice at 3 Tesla (T). Contrast-enhanced pulmonary perfusion scans were acquired with a temporally interleaved three-dimensional (3D) radial UTE (TE?=?0.08 ms) sequence in a breathhold (1 s time frames over a 33 s breathhold). The 3D breathheld volume was reconstructed into time-resolved perfusion datasets, and a composite vascular structure dataset. For structural comparison, a 5 min respiratory-gated 3D radial UTE scan was acquired. Data were analyzed by quantitative metrics and radiologist scoring.Appropriate time-course of contrast was seen in all subjects. Right ventricle to aorta transit times were 7.4?±?2.0 s. Relative lung enhancement was a factor of 8.4?±?1.5. Radiologist scoring showed similarly excellent visualization of the pulmonary arteries to the subsegmental level in breathheld (94% of cases) and respiratory-gated (100% of cases) acquisitions (P?=?0.33) despite the aggressive under sampling in the breathheld scan. Similarly, differentiation of lung tissue and airways was achieved by both acquisition methods.A time-resolved 3D radial UTE sequence for simultaneous imaging of pulmonary perfusion and co-registered vascular structure is feasible.
View details for DOI 10.1002/jmri.24520
View details for Web of Science ID 000346427800005
View details for PubMedID 24357054
Repeatability and Internal Consistency of Abdominal 2D and 4D Phase Contrast MR Flow Measurements
2013; 20 (6): 699-704
Atherosclerosis is the leading cause of cardiovascular disease (CVD) in the Western world. In the early development of atherosclerosis, vessel walls remodel outwardly such that the vessel luminal diameter is minimally affected by early plaque development. Only in the late stages of the disease does the vessel lumen begin to narrow-leading to stenoses. As a result, angiographic techniques are not useful for diagnosing early atherosclerosis. Given the absence of stenoses in the early stages of atherosclerosis, CVD remains subclinical for decades. Thus, methods of diagnosing atherosclerosis early in the disease process are needed so that affected patients can receive the necessary interventions to prevent further disease progression. Pulse wave velocity (PWV) is a biomarker directly related to vessel stiffness that has the potential to provide information on early atherosclerotic disease burden. A number of clinical methods are available for evaluating global PWV, including applanation tonometry and ultrasound. However, these methods only provide a gross global measurement of PWV-from the carotid to femoral arteries-and may mitigate regional stiffness within the vasculature. Additionally, the distance measurements used in the PWV calculation with these methods can be highly inaccurate. Faster and more robust magnetic resonance imaging (MRI) sequences have facilitated increased interest in MRI-based PWV measurements. This review provides an overview of the state-of-the-art in MRI-based PWV measurements. In addition, both gold standard and clinical standard methods of computing PWV are discussed.
View details for DOI 10.3978/j.issn.2223-3652.2014.03.04
View details for PubMedID 24834415
Aortic pulse wave velocity measurements with undersampled 4D flow-sensitive MRI: comparison with 2D and algorithm determination.
Journal of magnetic resonance imaging : JMRI
2013; 37 (4): 853-859
The aim of this study was to assess the repeatability and internal consistency of flow measurements in the renal arteries and pararenal aorta with the use of standard two-dimensional (2D) and novel four-dimensional (4D) phase contrast (PC) magnetic resonance imaging (MRI).Ten healthy volunteers were imaged with a radially undersampled 4D PC technique centered over the renal arteries and with four 2D PC slices placed in the supra/infrarenal aorta and the left/right renal arteries; this MRI exam was performed twice on each subject. Flow measurements in all four vessels were computed from 2D and 4D PC data sets. Student's t-tests (P < .05) were used to assess differences between in-flow (suprarenal aorta) and out-flow (infrarenal aorta + left renal artery + right renal artery) for the 2D and 4D techniques, to compare in- and out-flow, and to compare repeated measurements of 2D and 4D flow measurements.No significant differences were found in repeated measurements of 2D (P = .15) or 4D (P = .39) data. No significant difference was found between 2D (3.4 ± 2.8 mL/cardiac cycle) and 4D (3.5 ± 2.7 mL/cardiac cycle) in- and out-flow differences (P = .88). Out-flow was greater than in-flow for 2D measurements (P = .003); no difference was found for 4D measurements.The 2D and 4D techniques demonstrated strong repeatability and internal consistency of flow measurements in the renal arteries and pararenal aorta.
View details for DOI 10.1016/j.acra.2012.12.019
View details for Web of Science ID 000319308000006
View details for PubMedID 23510798
Dynamic and Static Magnetic Resonance Angiography of the Supra-aortic Vessels at 3.0 T Intraindividual Comparison of Gadobutrol, Gadobenate Dimeglumine, and Gadoterate Meglumine at Equimolar Dose
2013; 48 (3): 121-128
To compare pulse wave velocity (PWV) measurements obtained from radially undersampled 4D phase-contrast magnetic resonance imaging (PC-MRI) with 2D PC measurements and to evaluate four PWV algorithms.PWV was computed from radially undersampled 3D, 3-directionally velocity-encoded PC-MRI (4D) acquisitions performed on a 3T MR scanner in 18 volunteers. High temporal resolution 2D PC scans serving as a reference standard were available in 14 volunteers. Four PWV algorithms were tested: time-to-upstroke (TTU), time-to-peak (TTP), time-to-foot (TTF), and cross-correlation (XCorr). Bland-Altman analysis was used to determine inter- and intraobserver reproducibility and to compare differences between algorithms. Differences in age and PWV measurements were analyzed with Student's t-tests. The variability of age-corrected data was assessed with a Brown-Forsythe analysis of variance (ANOVA) test.2D (4.6-5.3 m/s) and 4D (3.8-4.8 m/s) PWV results were in agreement with previously reported values in healthy subjects. Of the four PWV algorithms, the TTU, TTF, and XCorr algorithms gave similar and reliable results. Average biases of +0.30 m/s and -0.01 m/s were determined for intra- and interobserver variability, respectively. The Brown-Forsythe test revealed that no differences in variability could be found between 2D and 4D PWV measurements.4D PC-MRI with radial undersampling provides reliable and reproducible measurements of PWV. TTU, TTF, and XCorr were the preferred PWV algorithms.
View details for DOI 10.1002/jmri.23877
View details for PubMedID 23124585
MR measures of renal perfusion, oxygen bioavailability and total renal blood flow in a porcine model: noninvasive regional assessment of renal function
NEPHROLOGY DIALYSIS TRANSPLANTATION
2012; 27 (1): 128-135
The purpose of this study was the intraindividual comparison of a 1.0 M and two 0.5 M gadolinium-based contrast agents (GBCA) using equimolar dosing in dynamic and static magnetic resonance angiography (MRA) of the supra-aortic vessels.In this institutional review board-approved study, a total of 20 healthy volunteers (mean ± SD age, 29 ± 6 years) underwent 3 consecutive supra-aortic MRA examinations on a 3.0 T magnetic resonance system. The order of GBCA (Gadobutrol, Gadobenate dimeglumine, and Gadoterate meglumine) was randomized with a minimum interval of 48 hours between the examinations. Before each examination and 45 minutes after each examination, circulatory parameters were recorded. Total GBCA dose per MRA examination was 0.1 mmol/kg with a 0.03 mmol/kg and 0.07 mmol/kg split for dynamic and static MRA, respectively, injected at a rate of 2 mL/s. Two blinded readers qualitatively assessed static MRA data sets independently using pairwise rankings (superior, inferior, and equal). In addition, quantitative analysis was performed with signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) evaluation as well as vessel sharpness analysis of static MRA using an in-house-developed semiautomated tool. Dynamic MRA was evaluated for maximal SNR. Statistical analysis was performed using the Cohen ?, the Wilcoxon rank sum tests, and mixed effects models.No significant differences of hemodynamic parameters were observed. In static MRA, Gadobutrol was rated superior to Gadoterate meglumine (P < 0.05) and equal to Gadobenate dimeglumine (P = 0.06) with good to excellent reader agreement (?, 0.66-0.83). In static MRA, SNR was significantly higher using 1.0 M Gadobutrol as compared with either 0.5 M agent (P < 0.05 and P < 0.05) and CNR was significantly higher as compared with Gadoterate meglumine (P < 0.05), whereas CNR values of Gadobutrol data sets were not significantly different as compared with Gadobenate dimeglumine (P = 0.13). Differences in CNR between Gadobenate dimeglumine and Gadoterate meglumine were not significant (P = 0.78). Differences in vessel sharpness between the different GBCAs were also not significant (P > 0.05). Maximal SNR in dynamic MRA using Gadobutrol was significantly higher than both comparators at the level of the proximal and distal internal carotid artery (P < 0.05 and P < 0.05; P < 0.05 and P < 0.05).At equimolar doses, 1.0 M Gadobutrol demonstrates higher SNR/CNR than do Gadobenate dimeglumine and Gadoterate meglumine, with superior image quality as compared with Gadoterate meglumine for dynamic and static carotid MRA. Despite the shortened bolus with Gadobutrol, no blurring of vessel edges was observed.
View details for DOI 10.1097/RLI.0b013e31827752b4
View details for Web of Science ID 000314369800001
View details for PubMedID 23211552
Reproducibility of Renal Perfusion MR Imaging in Native and Transplanted Kidneys Using Non-Contrast Arterial Spin Labeling
JOURNAL OF MAGNETIC RESONANCE IMAGING
2011; 33 (6): 1414-1421
Magnetic resonance imaging (MRI) may be a useful adjunct to current methods of evaluating renal function. MRI is a noninvasive imaging modality that has the ability to evaluate the kidneys regionally, which is lacking in current clinical methods. Other investigators have evaluated renal function with MRI-based measurements, such as with techniques to measure cortical and medullary perfusion, oxygen bioavailability and total renal blood flow (TRBF). However, use of all three techniques simultaneously, and therefore the relationships between these MRI-derived functional parameters, have not been reported previously.To evaluate the ability of these MRI techniques to track changes in renal function, we scanned 11 swine during a state of hyperperfusion with acetylcholine and a saline bolus and subsequently scanned during a state of hypoperfusion with the prolonged use of isoflurane anesthesia. For each time point, measurements of perfusion, oxygen bioavailability and TRBF were acquired. Measurements of perfusion and oxygen bioavailability were compared with measurements of TRBF for all swine across all time points.Cortical perfusion, cortical oxygen bioavailability, medullary oxygen bioavailability and TRBF significantly increased with the acetylcholine challenge. Cortical perfusion, medullary perfusion, cortical oxygen bioavailability and TRBF significantly decreased during isoflurane anesthesia. Cortical perfusion (Spearman's correlation coefficient = 0.68; P < 1 × 10(-6)) and oxygen bioavailability (Spearman's correlation coefficient = -0.60; P < 0.0001) correlated significantly with TRBF, whereas medullary perfusion and oxygen bioavailability did not correlate with TRBF.Our results demonstrate expected changes given the pharmacologically induced changes in renal function. Maintenance of the medullary oxygen bioavailability in low blood flow states may reflect the autoregulation particular to this region of the kidney. The ability to non-invasively measure all three parameters of kidney function in a single MRI examination and to evaluate the relationships between these functional parameters is potentially useful for evaluating the state of the human kidneys in situ in future studies.
View details for DOI 10.1093/ndt/gfr199
View details for Web of Science ID 000299957700023
View details for PubMedID 21622986
In Vivo Three-Dimensional MR Wall Shear Stress Estimation in Ascending Aortic Dilatation
JOURNAL OF MAGNETIC RESONANCE IMAGING
2011; 33 (3): 589-597
To examine both inter-visit and intra-visit reproducibility of a MR arterial spin labeling (ASL) perfusion technique in native and transplanted kidneys over a broad range of renal function.Renal perfusion exams were performed at 1.5 T in a total of 24 subjects: 10 with native and 14 with transplanted kidneys. Using a flow-sensitive alternating inversion recovery (FAIR) ASL scheme, 32 control/tag pairs were acquired and processed using a single-compartment model. Two FAIR-ASL MR exams were performed at least 24 h apart on all the subjects to assess inter-visit reproducibility. ASL perfusion measurements were also repeated back-to-back within one scanning session in 8 native subjects and in 12 transplant subjects to assess intra-visit reproducibility. Intra-class correlations (ICCs) and coefficients of variation (CVs) were calculated as metrics of reproducibility.Intra-visit ICCs ranged from 0.96 to 0.98 while CVs ranged from 4.8 to 6.0%. Inter-visit measurements demonstrated slightly more variation with ICCs from 0.89 to 0.94 and CVs from 7.6 to 13.1%. Medullary perfusion demonstrated greater variability compared with cortical blood flow: intra-visit ICCs from 0.72 to 0.78 and CVs from 16.7 to 26.7%, inter-visit ICCs from 0.13 to 0.63 and CVs from 19.8 to 37%.This study indicates that a FAIR-ASL perfusion technique is reproducible in the cortex of native and transplanted kidneys over a broad range in renal function. In contrast, perfusion measurements in the medulla demonstrated moderate to poor reproducibility for intra-visit and inter-visit measures respectively.
View details for DOI 10.1002/jmri.22552
View details for Web of Science ID 000291267700017
View details for PubMedID 21591011
Comparing Kidney Perfusion Using Noncontrast Arterial Spin Labeling MRI and Microsphere Methods in an Interventional Swine Model
2011; 46 (2): 124-131
To estimate surface-based wall shear stress (WSS) and evaluate flow patterns in ascending aortic dilatation (AscAD) using a high-resolution, time-resolved, three-dimensional (3D), three-directional velocity encoded, radially undersampled phase contrast MR sequence (4D PC-MRI).4D PC-MRI was performed in 11 patients with AscAD (46.3 ± 22.0 years) and 10 healthy volunteers (32.9 ± 13.4 years) after written informed consent and institutional review board approval. Following manual vessel wall segmentation of the ascending aorta (MATLAB, The Mathworks, Natick, MA), a 3D surface was created using spline interpolation. Spatial WSS variation based on surface division in 12 segments and temporal variation were evaluated in AscAD and normal aortas. Visual analysis of flow patterns was performed based on streamlines and particle traces using EnSight (v9.0, CEI, Apex, NC).AscAD was associated with significantly increased diastolic WSS, decreased systolic to diastolic WSS ratio, and delayed onset of peak WSS (all P < 0.001). Temporally averaged WSS was increased and peak systolic WSS was decreased. The maximum WSS in AscAD was on the anterior wall of the ascending aorta. Vortical flow with highest velocities along the anterior wall and increased helical flow during diastole were observed in AscAD compared with controls.Changes in WSS in the ascending aorta of AscAD correspond to observed alterations in flow patterns compared to controls.
View details for DOI 10.1002/jmri.22485
View details for Web of Science ID 000287951100010
View details for PubMedID 21563242
Arterial spin labeling MRI for assessment of perfusion in native and transplanted kidneys
MAGNETIC RESONANCE IMAGING
2011; 29 (1): 74-82
The purpose of this study was to assess the ability of a flow-sensitive alternating inversion recovery-arterial spin labeling (FAIR-ASL) technique to track renal perfusion changes during pharmacologic and physiologic alterations in renal blood flow using microspheres as a gold standard.Fluorescent microsphere and FAIR-ASL perfusion were compared in the cortex of the kidney for 11 swine across 4 interventional time points: (1) under baseline conditions, (2) during an acetylcholine and fluid bolus challenge to increase perfusion, (3) initially after switching to isoflurane anesthesia, and (4) after 2 hours of isoflurane anesthesia. In 10 of the 11 swine, a bag of ice was placed on the hilum of 1 kidney at the beginning of isoflurane administration to further reduce perfusion in 1 kidney.Both ASL and microspheres tracked the expected cortical perfusion changes (P < 0.02) across the interventions, including an increase in perfusion during the acetylcholine challenge and decrease during the administration of isoflurane. Both techniques also measured lower cortical perfusion in the iced compared with the non-iced kidneys (P ? 0.01). The ASL values were systematically lower compared with microsphere perfusion. Very good correlation (r = 0.81, P < 0.0001) was observed between the techniques, and the relationship appeared linear for perfusion values in the expected physiologic range (microsphere perfusion <550 mL/min/100 g) although ASL values saturated for perfusion >550 mL/min/100 g.Cortical perfusion measured with ASL correlated with microspheres and reliably detected changes in renal perfusion in response to physiologic challenge.
View details for DOI 10.1097/RLI.0b013e3181f5e101
View details for Web of Science ID 000286137000006
View details for PubMedID 22609830
Accuracy and Reproducibility of Phase-Contrast MR Imaging Measurements for CSF Flow
AMERICAN JOURNAL OF NEURORADIOLOGY
2010; 31 (7): 1331-1336
To apply a magnetic resonance arterial spin labeling (ASL) technique to evaluate kidney perfusion in native and transplanted kidneys.This study was compliant with the Health Insurance Portability and Accountability Act and approved by the institutional review board. Informed consent was obtained from all subjects. Renal perfusion exams were performed at 1.5 T in a total of 25 subjects: 10 with native and 15 with transplanted kidneys. A flow-sensitive alternating inversion recovery (FAIR) ASL sequence was performed with respiratory triggering in all subjects and under free-breathing conditions in five transplant subjects. Thirty-two control/tag pairs were acquired and processed using a single-compartment model. Perfusion in native and transplanted kidneys was compared above and below an estimated glomerular filtration rate (eGFR) threshold of 60 ml/min per 1.73 m² and correlations with eGFR were determined.In many of the transplanted kidneys, major feeding vessels in the coronal plane required a slice orientation sagittal to the kidney. Renal motion during the examination was observed in native and transplant subjects and was corrected with registration. Cortical perfusion correlated with eGFR in native (r=0.85, P=.002) and transplant subjects (r=0.61, P=.02). For subjects with eGFR >60 ml/min per 1.73 m², native kidneys demonstrated greater cortical (P=.01) and medullary (P=.04) perfusion than transplanted kidneys. For subjects with eGFR <60 ml/min per 1.73 m², native kidneys demonstrated greater medullary perfusion (P=.04) compared to transplanted kidneys. Free-breathing acquisitions provided renal perfusion measurements that were slightly lower compared to the coached/triggered technique, although no statistical differences were observed.In conclusion, FAIR-ASL was able to measure renal perfusion in subjects with native and transplanted kidneys, potentially providing a clinically viable technique for monitoring kidney function.
View details for DOI 10.1016/j.mri.2010.07.018
View details for Web of Science ID 000285570100010
View details for PubMedID 20850241
Fetal Origin of the Posterior Cerebral Artery Produces Left-Right Asymmetry on Perfusion Imaging
AMERICAN JOURNAL OF NEURORADIOLOGY
2010; 31 (3): 448-453
PCMR, widely used for the evaluation of blood flow, has been adopted for the assessment of cerebrospinal fluid flow in a variety of disorders. The purpose of this study was to evaluate the accuracy and reproducibility of 2 fast PCMR techniques for measuring CSF flow.Velocities were calculated from RPC and CPC images of fluid flowing in a tube at a constant velocity. Error and the COV were computed for average and peak velocities. Additionally, measurements of sinusoidally fluctuating flow and of CSF flow in 5 healthy volunteers were acquired with the RPC and CPC acquisitions.For constant velocity experiments, error for the RPC and CPC acquisitions averaged +1.15% and +8.91% and COVs averaged 1.29% and 3.01%, respectively. For peak velocities of >or=12.6 cm/s, error with RPC or CPC ranged from -33.3% to -36.9% and COVs were 0%-4% for RPC and 1%-7% for CPC. For peak velocities of 250%. For fluctuating flow, both acquisitions showed similar flow patterns. In volunteer studies, peak systolic and diastolic velocities were not significantly different.The RPC and CPC sequences measure velocities on the order of CSF flow with an average error of >or=9%. The 2 techniques significantly overestimate peak velocities <6.4 cm/s, with maximum errors of 209% and 276% and maximum COVs of 100% and 73% for the RPC and CPC sequences, respectively. Measurements of CSF velocities in human volunteers and of sinusoidally fluctuating phantom velocities did not differ significantly between the 2 techniques.
View details for DOI 10.3174/ajnr.A2039
View details for Web of Science ID 000281106700032
View details for PubMedID 20203113
Blood oxygen level-dependent and perfusion magnetic resonance imaging: detecting differences in oxygen bioavailability and blood flow in transplanted kidneys
MAGNETIC RESONANCE IMAGING
2010; 28 (1): 56-64
Fetal origin of the PCA is a common anatomic variation of the circle of Willis. On perfusion imaging, patients with unilateral fetal-type PCA may demonstrate left-right asymmetry that could mimic cerebrovascular disease. The aim of this study was to characterize the relationship between a fetal-type PCA and asymmetry of hemodynamic parameters derived from MR perfusion imaging.We retrospectively reviewed MR perfusion studies of 36 patients to determine the relationship between hemodynamic and vascular asymmetries in the PCA territory. Perfusion asymmetry indices for the PCA territory were computed from maps of rCBF, rCBV, MTT, T(max), and FMT. Vascular asymmetry indices were derived from calibers of the PCA-P1 segments relative to the posterior communicating arteries.Asymmetrically smaller values of FMT and T(max) were observed with unilateral fetal-type PCA, and these were strongly correlated with the degree of vascular asymmetry (Spearman's rho = 0.76 and 0.74, respectively, P < 1 x 10(-6)). Asymmetries of rCBF, MTT, and rCBV were neither significant nor related to vascular asymmetry.Faster perfusion transit times are seen for parameters sensitive to macrovascular transit effects (eg, FMT and T(max)) ipsilateral to fetal origin of the PCA in proportion to the degree of arterial asymmetry. Knowledge of this normal variation is critical in the interpretation of perfusion studies because asymmetry could mimic cerebrovascular pathology.
View details for DOI 10.3174/ajnr.A1858
View details for Web of Science ID 000275939000014
View details for PubMedID 19875474
Quantitative MR Measures of Intrarenal Perfusion in the Assessment of Transplanted Kidneys: Initial Experience
2009; 16 (9): 1077-1085
Functional magnetic resonance imaging (fMRI) is a powerful tool for examining kidney function, including organ blood flow and oxygen bioavailability. We have used contrast enhanced perfusion and blood oxygen level-dependent (BOLD) MRI to assess kidney transplants with normal function, acute tubular necrosis (ATN) and acute rejection. BOLD and MR-perfusion imaging were performed on 17 subjects with recently transplanted kidneys. There was a significant difference between medullary R2 values in the group with acute rejection (R2=16.2/s) compared to allografts with ATN (R2=19.8/s; P=.047) and normal-functioning allografts (R2=24.3/s;P=.0003). There was a significant difference between medullary perfusion measurements in the group with acute rejection (124.4+/-41.1 ml/100 g per minute) compared to those in patients with ATN (246.9+/-123.5 ml/100 g per minute; P=.02) and normal-functioning allografts (220.8+/-95.8 ml/100 g per minute; P=.02). This study highlights the utility of combining perfusion and BOLD MRI to assess renal function. We have demonstrated a decrease in medullary R2 (decrease deoxyhemoglobin) on BOLD MRI and a decrease in medullary blood flow by MR perfusion imaging in those allografts with acute rejection, which indicates an increase in medullary oxygen bioavailability in allografts with rejection, despite a decrease in blood flow.
View details for DOI 10.1016/j.mri.2009.05.044
View details for Web of Science ID 000276648600007
View details for PubMedID 19577402
Nephrogenic systemic fibrosis: Risk factors and incidence estimation
2007; 243 (1): 148-157
The purpose of this study was to evaluate prospectively a gadolinium-based perfusion technique for intrarenal blood flow in transplanted kidneys and to determine if magnetic resonance imaging (MRI) measurements of intrarenal perfusion could be used to differentiate between normal-functioning kidney allografts and allografts with acute tubular necrosis (ATN) or acute rejection.Twenty-one subjects were enrolled within 4 months of receiving a kidney transplant. A biopsy was performed on subjects to diagnose each allograft as having either ATN or acute rejection. A group of subjects with normal functioning transplants was also enrolled in our study. MRI perfusion images were acquired on a 1.5 T MRI system within 48 hours after biopsy using an echo planar, T2*-weighted sequence, and an injection of gadodiamide contrast agent administered at a dose of 0.1 mmol/kg. Scan parameters were: repetition time/echo time/flip = 1000 ms/30 ms/60 degrees , field of view = 340 x 340 mm, matrix = 128 x 64, slice thickness = 10 mm, and temporal resolution = 1.0 seconds. Cortical and medullary blood flow values were calculated.Medullary blood flow values were significantly (P = .02) lower in allografts undergoing acute rejection (121 +/- 41 mL/100 g/min) compared to normal-functioning allografts (221 +/- 96 mL/100 g/min) and those with ATN (247 +/- 124 mL/100 g/min). Cortical blood flow values were also significantly (P = .03) reduced in allografts with acute rejection (243 +/- 116 mL/100 g/min) compared to those with normal function (413 +/- 116 mL/100 g/min).Preliminary results indicate that MRI perfusion techniques may provide a means of determining noninvasively the viability of renal allografts, potentially alleviating the need for biopsy in some patients.
View details for DOI 10.1016/j.acra.2009.03.020
View details for Web of Science ID 000269067000007
View details for PubMedID 19539502
Cine flow measurements using phase contrast with undersampled projections: In vitro validation and preliminary results in vivo
JOURNAL OF MAGNETIC RESONANCE IMAGING
2006; 24 (4): 945-951
To retrospectively review data in 13 patients with biopsy-confirmed nephrogenic systemic fibrosis (NSF), assess the associated risk factors, and report the incidence of NSF at the authors' institution.This HIPAA-compliant study had institutional review board approval; informed consent was waived. Statistical analysis was performed for all available clinical and laboratory data in patients with biopsy-confirmed NSF. The data from the patients with NSF were compared with data from a control population of patients with renal insufficiency but who did not develop NSF.There were eight male and five female patients, aged 17-69 years, with a diagnosis of NSF. Within 6 months of diagnosis, all 13 patients had been exposed to gadodiamide and one had been exposed to gadobenate dimeglumine in addition to gadodiamide. At the time of contrast material-enhanced magnetic resonance (MR) imaging, all 13 patients had renal insufficiency (estimated glomerular filtration rate [eGFR] < 60 mL/min/1.73 m(2)) and were hospitalized for a proinflammatory event (major surgery, infection, or vascular event). The group with NSF had significantly decreased eGFR (P = .01), more proinflammatory events (P < .001), and more contrast-enhanced MR examinations per patient (P = .002) than did the control group.A combination of factors, including altered kidney function, inflammatory burden, and exposure to gadolinium-based contrast agents may all play a role in development of NSF. Alternative imaging should be considered in patients with these factors. If use of a gadolinium-based agent is clinically indicated, the referring physician and patient should be informed of the potential risk of developing NSF.
View details for DOI 10.1148/radiol.2431062144
View details for Web of Science ID 000245312500018
View details for PubMedID 17267695
Early emphysematous changes in asymptomatic smokers: Detection with He-3 MR imaging
2006; 239 (3): 875-883
To assess the accuracy of flow measurements in vitro and in vivo during scan times shorter than a breath-hold using a 2D cine phase contrast (PC) undersampled radial acquisition method, which may be useful for measuring flow, especially in vessels subject to motion during respiration.For in vitro assessment, a flow phantom was imaged at various flow rates and undersampling factors. For in vivo assessment, five normal subjects were imaged and the flow rate in the aorta was compared with the sum of the flow rates in the iliac arteries.For results in vitro, the accuracy of flow measurements was maintained with scan times as low as 13-17 seconds. For results in vivo, scans acquired in less than 25 seconds provided flow measurements in the aorta that corresponded well to the sum of flow measurements in the iliac arteries.The undersampled radial acquisition cine PC technique provided accurate flow measurements in a flow phantom and in healthy human volunteers in scan times shorter than a typical breath-hold.
View details for DOI 10.1002/jmri.20715
View details for Web of Science ID 000240882000031
View details for PubMedID 16969791
To prospectively compare apparent diffusion coefficient (ADC) measurements derived from diffusion-weighted hyperpolarized helium 3 (3He) magnetic resonance (MR) imaging with functional and structural findings using spirometric tests and thin-section computed tomography (CT) of the lungs in asymptomatic smokers and healthy nonsmokers of similar age.All studies were HIPAA compliant and were approved by the institutional review board. Informed consent was obtained. Ventilation and diffusion-weighted 3He MR images were obtained in healthy subjects: 11 smokers (five women, six men; mean age, 47 years+/-18 [standard deviation]; range, 23-73 years) and eight nonsmokers (<100 cigarettes in lifetime) (four women, four men; mean age, 46 years+/-16; range, 23-69 years). Mean ADC values for smokers and nonsmokers were compared with spirometric values, diffusing capacity of the lung for carbon monoxide (Dlco), age, and pack-years with Spearman rank correlation coefficient (rs) and multiple linear regression analysis. Mean ADC value and thin-section CT emphysema index of relative area less than -950 HU (RA950) were compared on a regional basis by using linear mixed-effect models.Mean ADC values and number of pack-years were significantly correlated (rs=0.60; 95% confidence interval (CI): 0.21, 1.00; P=.007); relationship remained significant after adjustment for age (P=.003). Dlco was strongly correlated with pack-years (rs=-0.63; 95% CI: -0.97, -0.29; P=.004). Negative correlations between mean ADC values and percentage predicted Dlco (rs=-0.79; 95% CI: -0.93, -0.64; P<.001) and the ratio of forced expiratory volume in 1 second to forced vital capacity (rs=-0.72; 95% CI: -0.92, -0.52; P=.001) were statistically significant. Correlations between spirometric values or RA950 and number of pack-years were not significant (.05 level).Correlations between mean ADC values and pulmonary function test measurements for diagnosing emphysema, especially Dlco, were statistically significant.
View details for DOI 10.1148/radiol.2393050111
View details for Web of Science ID 000237738600032
View details for PubMedID 16714465