Bio

Clinical Focus


  • Congenital Heart Disease
  • Diagnostic Radiology
  • Radiology

Academic Appointments


Professional Education


  • Internship:Kaiser Found Hosp San Fran (1995) CA
  • Stanford University Electrical Engineering (1990) CA
  • Fellowship:Stanford University School of Medicine (2000) CA
  • Residency:Stanford University School of Medicine (1999) CA
  • Board Certification: Diagnostic Radiology, American Board of Radiology (1999)
  • Medical Education:UCSF School of Medicine (1994) CA

Teaching

2013-14 Courses


Publications

Journal Articles


  • Computational fluid dynamic simulations for determination of ventricular workload in aortic arch obstructions JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY Coogan, J. S., Chan, F. P., LaDisa, J. F., Taylor, C. A., Hanley, F. L., Feinstein, J. A. 2013; 145 (2): 489-U535

    Abstract

    The cardiac workload associated with various types of aortic obstruction was determined using computational fluid dynamic simulations.Computed tomography image data were collected from 4 patients with 4 distinct types of aortic arch obstructions and 4 controls. The categorization of arch hypoplasia corresponded to the "A, B, C" nomenclature of arch interruption; a type "D" was added to represent diffuse arch hypoplasia. Measurements of the vessel diameter were compared against the normal measurements to determine the degree of narrowing. Three-dimensional models were created for each patient, and additional models were created for type A and B hypoplasia to represent 25%, 50%, and 75% diameter narrowing. The boundary conditions for the computational simulations were chosen to achieve realistic flow and pressures in the control cases. The simulations were then repeated after changing the boundary conditions to represent a range of cardiac and vascular adaptations. The resulting cardiac workload was compared with the control cases.Of the 4 patients investigated, 1 had aortic coarctation and 3 had aortic hypoplasia. The cardiac workload of the patients with 25% narrowing type A and B hypoplasia was not appreciably different from that of the control. When comparing the different arch obstructions, 75% type A, 50% type B, and 50% type D hypoplasia required a greater workload increase than 75% coarctation.The present study has determined the hemodynamic significance of aortic arch obstruction using computational simulations to calculate the cardiac workload. These results suggest that all types of hypoplasia pose more of a workload challenge than coarctation with an equivalent degree of narrowing.

    View details for DOI 10.1016/j.jtcvs.2012.03.051

    View details for Web of Science ID 000313634700032

    View details for PubMedID 22516390

  • Wall shear stress is decreased in the pulmonary arteries of patients with pulmonary arterial hypertension: An image-based, computational fluid dynamics study. Pulmonary circulation Tang, B. T., Pickard, S. S., Chan, F. P., Tsao, P. S., Taylor, C. A., Feinstein, J. A. 2012; 2 (4): 470-476

    Abstract

    Previous clinical studies in pulmonary arterial hypertension (PAH) have concentrated predominantly on distal pulmonary vascular resistance, its contribution to the disease process, and response to therapy. However, it is well known that biomechanical factors such as shear stress have an impact on endothelial health and dysfunction in other parts of the vasculature. This study tested the hypothesis that wall shear stress is reduced in the proximal pulmonary arteries of PAH patients with the belief that reduced shear stress may contribute to pulmonary endothelial cell dysfunction and as a result, PAH progression. A combined MRI and computational fluid dynamics (CFD) approach was used to construct subject-specific pulmonary artery models and quantify flow features and wall shear stress (WSS) in five PAH patients with moderate-to-severe disease and five age- and sex-matched controls. Three-dimensional model reconstruction showed PAH patients have significantly larger main, right, and left pulmonary artery diameters (3.5 ± 0.4 vs. 2.7 ± 0.1 cm, P = 0.01; 2.5 ± 0.4 vs. 1.9 ± 0.2 cm, P = 0.04; and 2.6 ± 0.4 vs. 2.0 ± 0.2 cm, P = 0.01, respectively), and lower cardiac output (3.7 ± 1.2 vs. 5.8 ± 0.6 L/min, P = 0.02.). CFD showed significantly lower time-averaged central pulmonary artery WSS in PAH patients compared to controls (4.3 ± 2.8 vs. 20.5 ± 4.0 dynes/cm(2), P = 0.0004). Distal WSS was not significantly different. A novel method of measuring WSS was utilized to demonstrate for the first time that WSS is altered in some patients with PAH. Using computational modeling in patient-specific models, WSS was found to be significantly lower in the proximal pulmonary arteries of PAH patients compared to controls. Reduced WSS in proximal pulmonary arteries may play a role in the pathogenesis and progression of PAH. This data may serve as a basis for future in vitro studies of, for example, effects of WSS on gene expression.

    View details for DOI 10.4103/2045-8932.105035

    View details for PubMedID 23372931

  • Rapid Pediatric Cardiac Assessment of Flow and Ventricular Volume With Compressed Sensing Parallel Imaging Volumetric Cine Phase-Contrast MRI AMERICAN JOURNAL OF ROENTGENOLOGY Hsiao, A., Lustig, M., Alley, M. T., Murphy, M., Chan, F. P., Herfkens, R. J., Vasanawala, S. S. 2012; 198 (3): W250-W259

    Abstract

    The quantification of cardiac flow and ventricular volumes is an essential goal of many congenital heart MRI examinations, often requiring acquisition of multiple 2D phase-contrast and bright-blood cine steady-state free precession (SSFP) planes. Scan acquisition, however, is lengthy and highly reliant on an imager who is well-versed in structural heart disease. Although it can also be lengthy, 3D time-resolved (4D) phase-contrast MRI yields global flow patterns and is simpler to perform. We therefore sought to accelerate 4D phase contrast and to determine whether equivalent flow and volume measurements could be extracted.Four-dimensional phase contrast was modified for higher acceleration with compressed sensing. Custom software was developed to process 4D phase-contrast images. We studied 29 patients referred for congenital cardiac MRI who underwent a routine clinical protocol, including cine short-axis stack SSFP and 2D phase contrast, followed by contrast-enhanced 4D phase contrast. To compare quantitative measurements, Bland-Altman analysis, paired Student t tests, and F tests were used.Ventricular end-diastolic, end-systolic, and stroke volumes obtained from 4D phase contrast and SSFP were well correlated (? = 0.91-0.95; r(2) = 0.83-0.90), with no statistically significant difference. Ejection fractions were well correlated in a subpopulation that underwent higher-resolution compressed-sensing 4D phase contrast (? = 0.88; r(2) = 0.77). Four-dimensional phase contrast and 2D phase contrast flow rates were also well correlated (? = 0.90; r(2) = 0.82). Excluding ventricles with valvular insufficiency, cardiac outputs derived from outlet valve flow and stroke volumes were more consistent by 4D phase contrast than by 2D phase contrast and SSFP.Combined parallel imaging and compressed sensing can be applied to 4D phase contrast. With custom software, flow and ventricular volumes may be extracted with comparable accuracy to SSFP and 2D phase contrast. Furthermore, cardiac outputs were more consistent by 4D phase contrast.

    View details for DOI 10.2214/AJR.11.6969

    View details for Web of Science ID 000301069000006

    View details for PubMedID 22358022

  • Combined respiratory and cardiac triggering improves blood pool contrast-enhanced pediatric cardiovascular MRI PEDIATRIC RADIOLOGY Vasanawala, S. S., Chan, F. P., Newman, B., Alley, M. T. 2011; 41 (12): 1536-1544

    Abstract

    Contrast-enhanced cardiac MRA suffers from cardiac motion artifacts and often requires a breath-hold.This work develops and evaluates a blood pool contrast-enhanced combined respiratory- and ECG-triggered MRA method.An SPGR sequence was modified to enable combined cardiac and respiratory triggering on a 1.5-T scanner. Twenty-three consecutive children referred for pediatric heart disease receiving gadofosveset were recruited in HIPAA-compliant fashion with IRB approval and informed consent. Children underwent standard non-triggered contrast-enhanced MRA with or without suspended respiration. Additionally, a free-breathing-triggered MRA was acquired. Triggered and non-triggered studies were presented in blinded random order independently to two radiologists twice. Anatomical structure delineation was graded for each triggered and non-triggered acquisition and the visual quality on triggered MRA was compared directly to that on non-triggered MRA.Triggered images received higher scores from each radiologist for all anatomical structures on each of the two reading sessions (Wilcoxon rank sum test, P?

    View details for DOI 10.1007/s00247-011-2196-y

    View details for Web of Science ID 000297621800005

    View details for PubMedID 21786125

  • Computational Simulations Demonstrate Altered Wall Shear Stress in Aortic Coarctation Patients Treated by Resection with End-to-end Anastomosis CONGENITAL HEART DISEASE LaDisa, J. F., Dholakia, R. J., Figueroa, C. A., Vignon-Clementel, I. E., Chan, F. P., Samyn, M. M., Cava, J. R., Taylor, C. A., Feinstein, J. A. 2011; 6 (5): 432-443

    Abstract

    Atherosclerotic plaque in the descending thoracic aorta (dAo) is related to altered wall shear stress (WSS) for normal patients. Resection with end-to-end anastomosis (RWEA) is the gold standard for coarctation of the aorta (CoA) repair, but may lead to altered WSS indices that contribute to morbidity.Computational fluid dynamics (CFD) models were created from imaging and blood pressure data for control subjects and age- and gender-matched CoA patients treated by RWEA (four males, two females, 15 ± 8 years). CFD analysis incorporated downstream vascular resistance and compliance to generate blood flow velocity, time-averaged WSS (TAWSS), and oscillatory shear index (OSI) results. These indices were quantified longitudinally and circumferentially in the dAo, and several visualization methods were used to highlight regions of potential hemodynamic susceptibility.The total dAo area exposed to subnormal TAWSS and OSI was similar between groups, but several statistically significant local differences were revealed. Control subjects experienced left-handed rotating patterns of TAWSS and OSI down the dAo. TAWSS was elevated in CoA patients near the site of residual narrowings and OSI was elevated distally, particularly along the left dAo wall. Differences in WSS indices between groups were negligible more than 5?dAo diameters distal to the aortic arch.Localized differences in WSS indices within the dAo of CoA patients treated by RWEA suggest that plaque may form in unique locations influenced by the surgical repair. These regions can be visualized in familiar and intuitive ways allowing clinicians to track their contribution to morbidity in longitudinal studies.

    View details for DOI 10.1111/j.1747-0803.2011.00553.x

    View details for Web of Science ID 000294919100005

    View details for PubMedID 21801315

  • Improved cardiovascular flow quantification with time-resolved volumetric phase-contrast MRI PEDIATRIC RADIOLOGY Hsiao, A., Alley, M. T., Massaband, P., Herfkens, R. J., Chan, F. P., Vasanawala, S. S. 2011; 41 (6): 711-720

    Abstract

    Cardiovascular flow is commonly assessed with two-dimensional, phase-contrast MRI (2-D PC-MRI). However, scan prescription and acquisition over multiple planes is lengthy, often requires direct physician oversight and has inconsistent results. Time-resolved volumetric PC-MRI (4-D flow) may address these limitations.We assess the degree of agreement and internal consistency between 2-D and 4-D flow quantification in our clinical population.Software enabling flow calculation from 4-D flow was developed in Java. With IRB approval and HIPAA compliance, 18 consecutive patients without shunts were identified who underwent both (1) conventional 2-D PC-MRI of the aorta and main pulmonary artery and (2) 4-D flow imaging. Aortic and pulmonary flow rates were assessed with both techniques.Both methods showed general agreement in flow rates (?: 0.87-0.90). Systemic and pulmonary arterial flow rates were well-correlated (?: 4-D 0.98-0.99, 2-D 0.93), but more closely matched with 4-D (P < 0.05, Brown-Forsythe). Pulmonary flow rates were lower than systemic rates for 2-D (P < 0.05, two-sample t-test). In a sub-analysis of patients without pulmonary or aortic regurgitation, 2-D showed improved correlation of flow rates while 4-D phase-contrast remained tightly correlated (?: 4-D 0.99-1.00, 2-D 0.99).4-D PC-MRI demonstrates greater consistency than conventional 2-D PC-MRI for flow quantification.

    View details for DOI 10.1007/s00247-010-1932-z

    View details for Web of Science ID 000290544500005

    View details for PubMedID 21221566

  • Computational Fluid Dynamic Simulations of Aortic Coarctation Comparing the Effects of Surgical- and Stent-Based Treatments on Aortic Compliance and Ventricular Workload CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS Coogan, J. S., Chan, F. P., Taylor, C. A., Feinstein, J. A. 2011; 77 (5): 680-691

    Abstract

    In this work, we examine the effects of stent-induced aortic stiffness on cardiac workload and blood pressure using computational fluid dynamic simulations. Background: Treatment of aortic coarctation (CoA) consists of either open, surgical repair or angioplasty with or without stenting. Although stenting is a minimally invasive alternative to surgery, aortic stiffness increases in the stented section. Concern over this increased stiffness has long been argued to be detrimental to the overall vascular health of the patient.MR imaging was performed on a 15-year-old female with CoA. A 3D model of the large thoracic arteries was created, and the heart and downstream vasculature were represented by lumped parameter models at the model inlet and outlets, respectively. A deformable wall assumption was used in conjunction with variable wall properties and tissue support, and 3D velocity, pressure, and wall dynamics were computed. The lumped parameter values and wall properties were tuned to match the mean flow and aortic deformation as measured by MRI. The CoA was then virtually removed from the model representing an end-to-end surgical correction. In a second model, the repaired section was prescribed to be nearly rigid, representing stenting. All other variables remained the same.When compared to surgery, stenting resulted in clinically negligible increases in cardiac work (0.4%) and no change in mean blood pressure.This pilot study suggests CoA stenting may not affect cardiac work to any significant degree as is commonly believed in the clinical community.

    View details for DOI 10.1002/ccd.22878

    View details for Web of Science ID 000288793200019

    View details for PubMedID 21061250

  • Three-Dimensional Hemodynamics in the Human Pulmonary Arteries Under Resting and Exercise Conditions ANNALS OF BIOMEDICAL ENGINEERING Tang, B. T., Fonte, T. A., Chan, F. P., Tsao, P. S., Feinstein, J. A., Taylor, C. A. 2011; 39 (1): 347-358

    Abstract

    The biomechanical forces associated with blood flow have been shown to play a role in pulmonary vascular cell health and disease. Therefore, the quantification of human pulmonary artery hemodynamic conditions under resting and exercise states can be useful in investigating the physiology of disease development and treatment outcomes. In this study, a combined magnetic resonance imaging and computational fluid dynamics approach was used to quantify pulsatile flow fields, wall shear stress (WSS), oscillations in WSS (OSI), and energy efficiency in six subject-specific models of the human pulmonary vasculature with high spatial and temporal resolution. Averaging over all subjects, WSS was found to increase from 19.8±4.0 to 51.8±6.7 dynes/cm2, and OSI was found to decrease from 0.094±0.016 to 0.081±0.015 in the proximal pulmonary arteries between rest and exercise conditions (p<0.05). These findings demonstrate the localized, biomechanical effects of exercise. Furthermore, an average decrease of 10% in energy efficiency was noted between rest and exercise. These data indicate the amount of energy dissipation that typically occurs with exercise and may be useful in future surgical planning applications.

    View details for DOI 10.1007/s10439-010-0124-1

    View details for Web of Science ID 000287213100030

    View details for PubMedID 20640512

  • Behcet's disease and heart transplantation: A word of caution JOURNAL OF HEART AND LUNG TRANSPLANTATION Hollander, S. A., Yasnovsky, J. R., Reinhartz, O., Chan, F., Sandborg, C., Hunt, S., Bernstein, D., Chin, C. 2010; 29 (11): 1306-1308

    Abstract

    Behcet's disease is a rare autoimmune disease characterized by oral and genital ulcers, and by multisystem disease, including arthritis, neurologic complications and vasculitis. Large-vessel and coronary artery aneurysms are often an indication for surgery, but the return of aneurysms, thrombosis, and the tendency to exhibit an exaggerated inflammatory response at puncture sites (pathergy) complicate surgical recovery. As such, cardiac transplantation, which requires atrial and large-vessel anastomoses, has not been reported in patients with Behcet's disease. We report the first orthotopic heart transplant with >1-year survival in a patient with Behcet's disease despite major complications. The investigators remain pessimistic about cardiac transplantation in patients with Behcet's disease until advances in preventing recurrent vascular pathology ensue.

    View details for DOI 10.1016/j.healun.2010.07.010

    View details for Web of Science ID 000284030700015

    View details for PubMedID 20822920

  • Institutional experience with laparoscopic partial splenectomy for hereditary spherocytosis JOURNAL OF PEDIATRIC SURGERY Slater, B. J., Chan, F. P., Davis, K., Dutta, S. 2010; 45 (8): 1682-1686

    Abstract

    Moderate to severe hereditary spherocytosis (HS) is treated with splenectomy. However, total splenectomy leads to decreased immunologic function with the risk of overwhelming postsplenectomy sepsis. Splenic preservation is postulated as a method to avoid this potentially fatal complication. Although mainly performed through laparotomy, we report our experience with a laparoscopic approach to partial splenectomy for HS.A retrospective review was conducted on 9 laparoscopic partial splenectomies performed for HS at our institution. Follow-up was from 1 to 3.5 years. Data included preoperative and postoperative hemoglobin, absolute reticulocyte count, splenic size, operative time, complications, and length of stay.All patients successfully underwent laparoscopic partial splenectomy with a radiologically determined upper-pole remnant of 10% to 30% and preservation of the blood supply through the upper short gastric arteries. The mean preoperative spleen length was 13 cm. Mean hospital stay was 3.6 days (range, 1-6 days). There was 1 intraoperative complication (a small bowel tear during spleen extraction) and 2 minor postoperative complications (ileus and wound infection). One patient underwent completion total splenectomy 2 years after partial splenectomy.Laparoscopic partial splenectomy is a feasible and effective procedure that addresses the hematologic consequences of HS while retaining a portion of functional spleen, in addition to conferring the advantages of laparoscopy.

    View details for DOI 10.1016/j.jpedsurg.2010.01.037

    View details for Web of Science ID 000280933100018

    View details for PubMedID 20713220

  • Congenital extrahepatic portosystemic shunt associated with heterotaxy and polysplenia PEDIATRIC RADIOLOGY Newman, B., Feinstein, J. A., Cohen, R. A., Feingold, B., Kreutzer, J., Patel, H., Chan, F. P. 2010; 40 (7): 1222-1230

    Abstract

    Heterotaxy with polysplenia is associated with many cardiovascular anomalies including the occasional occurrence of congenital extrahepatic portosystemic shunts (CEPS). Missing this anomaly can lead to inappropriate and ineffective therapy.To emphasize the importance and associated anatomy of CEPS in conjunction with heterotaxy with polysplenia.Review of three young children who presented with cyanosis and pulmonary hypertension without a cardiac etiology. They were known (1) or discovered (2) to have heterotaxy with polysplenia.There was absence of the intrahepatic inferior vena cava (IVC) with azygos or hemiazygos continuation in all three cases. In spite of normal liver function, they were discovered to have large portosystemic shunts, splenorenal in location, along with diffuse peripheral pulmonary arterial dilatation suggestive of CEPS (Abernethy malformation) with hepatopulmonary or, more accurately, portopulmonary syndrome. All CEPS were ipsilateral to the spleens. Patency of the portal veins in these cases allowed for percutaneous shunt closure with resolution of cyanosis.CEPS is associated with heterotaxy with polysplenia and can be symptomatic because of pulmonary arteriovenous (AV) shunting. Portal and hepatic vein patency are critical for determining feasibility of CEPS closure.

    View details for DOI 10.1007/s00247-009-1508-y

    View details for Web of Science ID 000278582300007

    View details for PubMedID 20069288

  • Breathheld Autocalibrated Phase-Contrast Imaging JOURNAL OF MAGNETIC RESONANCE IMAGING Lew, C., Alley, M. T., Spielman, D. M., Bammer, R., Chan, F. P. 2010; 31 (4): 1004-1014

    Abstract

    To compare generalized autocalibrating partially parallel acquisitions (GRAPPA), modified sensitivity encoding (mSENSE), and SENSE in phase-contrast magnetic resonance imaging (PC-MRI) applications.Aliasing of the torso can occur in PC-MRI applications. If the data are further undersampled for parallel imaging, SENSE can be problematic in correctly unaliasing signals due to coil sensitivity maps that do not match that of the aliased volume. Here, a method for estimating coil sensitivities in flow applications is described. Normal volunteers (n = 5) were scanned on a 1.5 T MRI scanner and underwent PC-MRI scans using GRAPPA, mSENSE, SENSE, and conventional PC-MRI acquisitions. Peak velocity and flow through the aorta and pulmonary artery were evaluated.Bland-Altman statistics for flow in the aorta and pulmonary artery acquired with mSENSE and GRAPPA methods (R = 2 and R = 3 cases) have comparable mean differences to flow acquired with conventional PC-MRI. GRAPPA and mSENSE PC-MRI have more robust measurements than SENSE when there is aliasing artifact caused by insufficient coil sensitivity maps. For peak velocity, there are no considerable differences among the mSENSE, GRAPPA, and SENSE reconstructions and are comparable to conventional PC-MRI.Flow measurements of images reconstructed with autocalibration techniques have comparable agreement with conventional PC-MRI and provide robust measurements in the presence of wraparound.

    View details for DOI 10.1002/jmri.22127

    View details for Web of Science ID 000276328200028

    View details for PubMedID 20373447

  • MR and CT imaging of the pediatric patient with structural heart disease. Seminars in thoracic and cardiovascular surgery. Pediatric cardiac surgery annual Chan, F. P. 2009: 99-105

    Abstract

    Cardiac magnetic resonance imaging (MRI) and computed tomography (CT) are imaging modalities increasingly used in the diagnosis and management of structural heart disease. They are powerful imaging tools that have individual strengths and weaknesses. Rational choice between MRI and CT should be based on a sound understanding of these issues. Management guidelines that incorporate the use of MRI and CT are currently being developed, and their utilizations are expected to grow rapidly in the future.

    View details for DOI 10.1053/j.pcsu.2009.01.009

    View details for PubMedID 19349022

  • Time-resolved three-dimensional imaging of the left atrium and pulmonary veins in the interventional suite - A comparison between muttisweep gated rotational three-dimensional reconstructed fluoroscopy and multislice computed tomography HEART RHYTHM Al-Ahmad, A., Wigstroem, L., Sandner-Porkristl, D., Wang, P. J., Zei, P. C., Boese, J., Lauritsch, G., Moore, T., Chan, F., Fahrig, R. 2008; 5 (4): 513-519

    Abstract

    Cardiac computed tomography (CT) is commonly used to visualize left atrial (LA) anatomy for ablation of atrial fibrillation. We have developed a new imaging technique that allows acquisition and visualization of three-dimensional (3D) cardiac images in the catheter lab.We sought to compare LA and pulmonary vein (PV) dimensions acquired using gated multisweep rotational fluoroscopy (C-arm CT) system and multislice computed tomography (MSCT) in an in vivo porcine model.A Siemens AXIOM Artis dTA C-arm system (Siemens AG, Medical Solutions) was modified to allow acquisition of four bidirectional sweeps during synchronized acquisition of the electrocardiogram signal to allow retrospective gating. C-arm CT image volumes were then reconstructed. Gated MSCT (SOMATOM Sensation 16 and 64, Siemens AG, Medical Solutions) and C-arm CT images were acquired in six animals. The two main PV diameters were measured in orthogonal axes. LA volumes were calculated. C-arm CT measurements were compared with the MSCT measurements.The average PV diameters using the C-arm CT were 2.24 x 1.35 cm, versus 2.27 x 1.38 cm for CT. The average difference was 0.034 cm (1.9%) between the C-arm CT and standard CT. The average LA volume using MSCT was 49.1 +/- 12.7 cm(3), as compared with 51.0 +/- 8.7 cm(3) obtained by the C-arm CT. The average difference between the C-arm CT and the MSCT was 1.9 cm(3) (3.7%). There were no significant differences in either the PV or LA measurements.Visualization of 3D cardiac anatomy during ablation procedures is possible and highly accurate. The 3D cardiac reconstructions acquired during ablation procedures will be valuable for procedural planning and guidance.

    View details for DOI 10.1016/j.hrthm.2007.12.027

    View details for Web of Science ID 000254596600003

    View details for PubMedID 18362018

  • MR and CT imaging of the pediatric patient with structural heart disease. Seminars in thoracic and cardiovascular surgery Chan, F. P. 2008; 20 (4): 393-399

    Abstract

    Cardiac MRI and CT are imaging modalities increasingly employed in the diagnosis and management of structural heart disease. They are powerful imaging tools that have individual strengths and weaknesses. Rational choice between MRI and CT should be based on a sound understanding of these issues. Management guidelines that incorporate the use of MRI and CT are currently being developed, and their utilizations are expected to grow rapidly in the future.

    View details for DOI 10.1053/j.semtcvs.2008.11.006

    View details for PubMedID 19251181

  • SENSE phase-constrained magnitude reconstruction with iterative phase refinement MAGNETIC RESONANCE IN MEDICINE Lew, C., Pineda, A. R., Clayton, D., Spielman, D., Chan, F., Bammer, R. 2007; 58 (5): 910-921

    Abstract

    Conventional sensitivity encoding (SENSE) reconstruction is based on equations in the complex domain. However, for many MRI applications only the magnitude is relevant. If there exists an estimate of the underlying phase information, a magnitude-only phase-constrained reconstruction can help to improve the conditioning of the SENSE reconstruction problem. Consequently, this reduces g-factor-related noise enhancement. In previous attempts at phase-constrained SENSE reconstruction, image quality was hampered by strong aliasing artifacts resulting from inadequate phase estimates and high sensitivity to phase errors. If a full-resolution phase image is used, a significant reduction in aliasing errors and better noise properties compared to SENSE can be obtained. An iterative scheme that improves the phase estimate to better approximate the phase is presented. The mathematical framework of the new approach is provided together with comparisons of conventional SENSE, phase-constrained SENSE, and the new phase-refinement method. Both theory and experimental verification demonstrate significantly better noise performance at high reduction factors, i.e., close to the theoretical limit. For applications that need only magnitude data, an iterative phase-constrained SENSE reconstruction can provide substantial SNR improvement over SENSE reconstruction and less artifacts than phase-constrained SENSE.

    View details for DOI 10.1002/mrm.21284

    View details for Web of Science ID 000250560000008

    View details for PubMedID 17969127

  • Peak velocity and flow quantification validation for sensitivity-encoded phase-contrast MR imaging ACADEMIC RADIOLOGY Lew, C. D., Alley, M. T., Bammer, R., Spielman, D. M., Chan, F. P. 2007; 14 (3): 258-269

    Abstract

    Phase-contrast (PC) magnetic resonance imaging (MRI) technique has important clinical applications in blood flow quantification and pressure gradient estimation by velocity measurement. Parallel imaging using sensitivity encoding (SENSE) may substantially reduce scan time. We demonstrate the utility of PC-MRI measurements accelerated by SENSE under clinical conditions.Accuracy and repeatability of a SENSE-PC implementation was evaluated by comparison with a commercial PC sequence with five normal volunteers. Twenty-six patients were then scanned with SENSE-PC at reduction factors (R = 1, 2, and 3). Blood flow and peak velocity were measured in the aorta and pulmonary trunk in 16 patients and peak velocity was measured at the coarctation of 10 patients. Quantitative flow, shunt ratio, and peak velocity measurements obtained with different reduction factors were compared using correlation, linear regression, and Bland-Altman statistics. All studies were approved by an Institutional Review Board, and informed consent was acquired from all subjects.The correlation coefficients for all comparisons were >0.962 and with high statistical significance (P < .01). Linear regression slopes ranged between 0.96 and 1.11 for flow and 0.88 to 1.05 for peak velocity. For flow, the Bland-Altman statistics yielded a total mean difference ranging from -0.02 to 0.05) L/minute with 2 standard of deviation limits ranging from -0.52 to 0.75 L/minute. For peak velocity, the total mean difference ranged from -0.10 to -0.004) milliseconds with 2-SD limits ranging from -0.062 to 0.46 milliseconds. R = 3 to R = 1 comparisons had greater 2-SD limits than R = 2 to R = 1 comparisons.SENSE PC-MRI measurements for flow and pressure gradient estimation were comparable to conventional PC-MRI.

    View details for DOI 10.1016/j.acra.2006.11.008

    View details for Web of Science ID 000246861100003

    View details for PubMedID 17307658

  • Echocardiographic diagnosis of persistent fifth aortic arch ECHOCARDIOGRAPHY-A JOURNAL OF CARDIOVASCULAR ULTRASOUND AND ALLIED TECHNIQUES Bernheimer, J., Friedberg, M., Chan, F., Silverman, N. 2007; 24 (3): 258-262

    Abstract

    We describe echocardiography and computerized tomographic imaging findings in the two subtypes of fifth aortic arch in infants. In the first form, the fifth aortic arch creates a systemic to systemic connection extending from the ascending to the descending aorta. When this form appears in isolation, it does not cause hemodynamic disturbance, although associated cardiac lesions, such as aortic coarctation or interruption and patent ductus arteriosus, may influence the clinical presentation. In the second form the fifth aortic arch connects the systemic and pulmonary circulations from persistent connections between the embryological fifth and sixth arches, which may cause significant hemodynamic disturbance from left to right shunting. Although this form has been associated with a wide array of congenital cardiac lesions, this is the first description of 5th aortic arch in association with atrioventricular septal defect and double outlet right ventricle.

    View details for DOI 10.1111/j.1540-8175.2007.00383.x

    View details for Web of Science ID 000244343900007

    View details for PubMedID 17313637

  • Effects of exercise and respiration on hemodynamic efficiency in CFD simulations of the total cavopulmonary connection ANNALS OF BIOMEDICAL ENGINEERING Marsden, A. L., Vignon-Clementel, I. E., Chan, F. P., Feinstein, J. A., Taylor, C. A. 2007; 35 (2): 250-263

    Abstract

    Congenital heart defects with a single functional ventricle, such as hypoplastic left heart syndrome and tricuspid atresia, require a staged surgical approach to separate the systemic and pulmonary circulations. Ultimately, the venous or pulmonary side of the heart is bypassed by directly connecting the vena cava to the pulmonary arteries with a modified t-shaped junction. The Fontan procedure (total cavopulmonary connection, TCPC) completes this process of separation. To date, computational fluid dynamics (CFD) simulations in this low pressure, passive flow, intrathoracic system have neglected the presumed important effects of respiration on physiology and higher "stress" states such as with exercise have never been considered. We hypothesize that incorporating effects of respiration and exercise would provide more realistic estimates of TCPC performance. Time-dependent, 3D blood flow simulations are performed by a custom finite element solver for two patient-specific Fontan models with a novel respiration model, developed to generate physiologic time-varying flow conditions. Blood flow features, pressure, and energy efficiency are analyzed at rest and with increasing flow rates to simulate exercise conditions. The simulations produce realistic pressure and flow data, comparable to that measured by catheterization and echocardiography, and demonstrate substantial increases in energy dissipation (i.e. decreased performance) with exercise and respiration due to increasing intensity of small scale vortices in the flow. As would be expected, these changes are highly dependent on patient-specific anatomy and Fontan geometry. We propose that respiration and exercise should be incorporated into TCPC CFD simulations to provide increasingly realistic evaluations of TCPC performance.

    View details for DOI 10.1007/s10439-006-9224-3

    View details for Web of Science ID 000243471200008

    View details for PubMedID 17171509

  • Images in cardiovascular medicine. Cardiac magnetic resonance imaging for myocarditis: effective use in medical decision making. Circulation Fenster, B. E., Chan, F. P., Valentine, H. A., Yang, E., McConnell, M. V., Berry, G. J., Yang, P. C. 2006; 113 (22): e842-3

    View details for PubMedID 16754807

  • Images in cardiovascular medicine. Near sudden death from cardiac lipoma in an adolescent. Circulation Friedberg, M. K., Chang, I. L., Silverman, N. H., Ramamoorthy, C., Chan, F. P. 2006; 113 (21): e778-9

    View details for PubMedID 16735681

  • Peri-infarct ischemia determined by cardiovascular magnetic resonance evaluation of myocardial viability and stress perfusion predicts future cardiovascular events in patients with severe ischemic cardiomyopathy JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE Tsukiji, M., Nguyen, P., Narayan, G., Hellinger, J., Chan, F., Herfkens, R., Pauly, J. M., McConnell, M. V., Yang, P. C. 2006; 8 (6): 773-779

    Abstract

    We assessed whether cardiovascular magnetic resonance imaging (CMR) of peri-infarct ischemia provides prognostic information in severe ischemic cardiomyopathy (ICM) patients referred for revascularization.Twenty-one patients with severe ICM were recruited prospectively for combined stress adenosine perfusion, late gadolinium enhancement, and rest perfusion studies. The patients were followed for in-hospital and post-discharge cardiovascular events.During 12+/- 9.8 months follow-up, 67% of the patients with peri-infarct ischemia and 13% of the patients without peri-infarct ischemia had cardiovascular events (p = 0.03). CONCLUSION. In severe ICM patients, the presence of peri-infarct ischemia was associated with a higher incidence of cardiovascular events.

    View details for DOI 10.1080/10976640600737615

    View details for Web of Science ID 000241485600002

    View details for PubMedID 17060098

  • Primary interpretation of thoracic MDCT images using coronal reformations AMERICAN JOURNAL OF ROENTGENOLOGY Kwan, S. W., Partik, B. L., Zinck, S. E., Chan, F. P., Kee, S. T., Leung, A. N., Voracek, M., Rubin, G. D. 2005; 185 (6): 1500-1508

    Abstract

    The objective of this study was to evaluate the accuracy and efficiency of primary interpretation of thoracic MDCT using coronal reformations as compared with transverse images.Fifty patients (18 females, 32 males; age range, 15-93 years; mean age, 63.6 years) underwent 4-MDCT of the chest (detector width, 1 mm; beam pitch, 1.5). Contrast material was administered in 20 of the 50 patients. Coronal and transverse sections were reformatted into 5-mm-thick sections at 3.5-mm intervals. All available image and clinical data consensually reviewed by two thoracic radiologists served as the reference standard. Subsequently, three other thoracic radiologists independently evaluated reformatted coronal and transverse images at two separate review sessions. Each image set was assessed in 58 categories for abnormalities of the lungs, mediastinum, pleura, chest wall, diaphragm, abdomen, and skeleton. Interpretation times and number of images assessed were recorded. Sensitivity, specificity, and interobserver concordance were calculated. Differences in mean sensitivities and specificities were evaluated with Wilcoxon's signed rank test.The most common findings identified were pulmonary nodules (n = 73, transverse images; n = 72, coronal images) and emphysema (n = 45, transverse; n = 40, coronal). The mean detection sensitivity of all lesions was significantly (p = 0.001) lower on coronal (44% +/- 26% [SD]) than on transverse (51% +/- 22%) images, whereas the mean detection specificity was significantly (p = 0.005) higher (96% +/- 5% vs 95% +/- 6%, respectively). Reporting findings for significantly (p < 0.001) fewer coronal images (mean, 63.0 +/- 4.6 images) than transverse images (mean, 91.9 +/- 8.8 images) took significantly (p = 0.025) longer (mean, 263 +/- 56 sec vs 238 +/- 45 sec, respectively).Primary interpretation of thoracic MDCT is less sensitive and more time-consuming using 5-mm-thick coronal reformations as compared with transverse images.

    View details for DOI 10.2214/AJR.04.1335

    View details for Web of Science ID 000233510600019

    View details for PubMedID 16304004

  • MDCT angiography of pediatric vascular diseases of the abdomen, pelvis, and extremities PEDIATRIC RADIOLOGY Chan, F. P., Rubin, G. D. 2005; 35 (1): 40-53

    Abstract

    Multi-detector-row computed tomography (MDCT) enables rapid, noninvasive, high-resolution, and three-dimensional imaging of pediatric vascular diseases. In this paper, we explore the adaptation of the MDCT angiographic principles to pediatric patients for vascular diseases of the abdomen, pelvis, and extremities. Special emphasis is placed on the practical aspects of how to perform these studies. Optimizations of scan parameters, contrast medium usage, radiation dose, and three-dimensional image processing are discussed in detail. We provide practical guidance on how to choose between MR angiography and CT angiography. Finally, we review important pediatric vascular diseases, categorized into traumatic injuries, inherited vascular diseases, congenital vascular diseases, vasculitides, and surgical planning and assessment. In each category, we discuss how CT angiography can be tailored to maximize its clinical benefits.

    View details for DOI 10.1007/s00247-004-1371-9

    View details for Web of Science ID 000226382100006

    View details for PubMedID 15692842

  • Computed tomography angiography - State-of-the-art imaging using multidetector-row technology JOURNAL OF COMPUTER ASSISTED TOMOGRAPHY Napoli, A., Fleischmann, D., Chan, F. P., Catalano, C., Hellinger, J. C., Passariello, R., Rubin, G. D. 2004; 28: S32-S45

    Abstract

    Multidetector-row computed tomography (MDCT) is an essential diagnostic modality for many clinical algorithms. This is particularly true with regard to the evaluation of cardiovascular disease. As a result of increased image acquisition speed, improved spatial resolution, and greater scan volume, MDCT angiography (computed tomography angiography [CTA]) has become an excellent noninvasive imaging technique, replacing intra-arterial digital subtraction angiography for most vascular territories. The clinical success of CTA depends on precise synchronization of image acquisition with optimal vascular enhancement. As technology continuously evolves, however, this task can be challenging. It remains important to have a fundamental knowledge of the principles behind technical parameters and contrast medium administration. This article reviews these essential principles, followed by an overview of current clinical applications.

    View details for Web of Science ID 000222968800008

    View details for PubMedID 15258492

  • Time-resolved 3-dimensional velocity mapping in the thoracic aorta - Visualization of 3-directional blood flow patterns in healthy volunteers and patients JOURNAL OF COMPUTER ASSISTED TOMOGRAPHY Markl, M., Draney, M. T., Hope, M. D., Levin, J. M., Chan, F. P., Alley, M. T., Pelc, N. J., Herfkens, R. J. 2004; 28 (4): 459-468

    Abstract

    An analysis of thoracic aortic blood flow in normal subjects and patients with aortic pathologic findings is presented. Various visualization tools were used to analyze blood flow patterns within a single 3-component velocity volumetric acquisition of the entire thoracic aortaTime-resolved, 3-dimensional phase-contrast magnetic resonance imaging (3D CINE PC MRI) was employed to obtain complete spatial and temporal coverage of the entire thoracic aorta combined with spatially registered 3-directional pulsatile blood flow velocities. Three-dimensional visualization tools, including time-resolved velocity vector fields reformatted to arbitrary 2-dimensional cut planes, 3D streamlines, and time-resolved 3D particle traces, were applied in a study with 10 normal volunteers. Results from 4 patient examinations with similar scan prescriptions to those of the volunteer scans are presented to illustrate flow features associated with common pathologic findings in the thoracic aorta.Previously reported blood flow patterns in the thoracic aorta, including right-handed helical outflow, late systolic retrograde flow, and accelerated passage through the aortic valve plane, were visualized in all volunteers. The effects of thoracic aortic disease on spatial and temporal blood flow patterns are illustrated in clinical cases, including ascending aortic aneurysms, aortic regurgitation, and aortic dissection.Time-resolved 3D velocity mapping was successfully applied in a study of 10 healthy volunteers and 4 patients with documented aortic pathologic findings and has proven to be a reliable tool for analysis and visualization of normal characteristic as well as pathologic flow features within the entire thoracic aorta.

    View details for Web of Science ID 000222861400005

    View details for PubMedID 15232376

  • Steady-state free precession MR imaging: Improved myocardial tag persistence and signal-to-noise ratio for analysis of myocardial motion RADIOLOGY Markl, M., Reeder, S. B., Chan, F. P., Alley, M. T., Herfkens, R. J., Pelc, N. J. 2004; 230 (3): 852-861

    Abstract

    Tagging with balanced steady-state free-precession (SSFP) magnetic resonance (MR) imaging by using a steady-state storage scheme for myocardial motion analysis was evaluated. Signal-to-noise ratio (SNR), blood-tissue contrast, and tag persistence in volunteers and phantoms showed improved performance of SSFP imaging with tagging compared with that of radiofrequency spoiled gradient-echo (SPGR) MR imaging with tagging. Choice of flip angle with SSFP imaging involved a trade-off among SNR, blood-tissue contrast, and tag persistence. Increased SNR and tag persistence can be achieved simultaneously with SSFP imaging compared with SPGR tagging methods. As a result, the proposed technique may be useful for analysis of diastolic ventricular function.

    View details for DOI 10.1148/radiol.2303030181

    View details for Web of Science ID 000189186500037

    View details for PubMedID 14990847

  • Cardiac multidetector-row computed tomography: Principles and applications SEMINARS IN ROENTGENOLOGY Chan, F. P. 2003; 38 (4): 294-302
  • Composite spirometric-computed tomography outcome measure in early cystic fibrosis lung disease AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE Robinson, T. E., Leung, A. N., Northway, W. H., Blankenberg, F. G., Chan, F. P., Bloch, D. A., Holmes, T. H., Moss, R. B. 2003; 168 (5): 588-593

    Abstract

    With the advent of therapies aimed at young patients with cystic fibrosis, who have mildly reduced pulmonary function, the need for improved outcome measures that discriminate treatment effects has become important. Pulmonary function measurements or chest high-resolution computed tomography (HRCT) scores have been separately used to assess interventions. We evaluated these modalities separately and together during a treatment study to develop a more sensitive outcome measure. In a 1-year trial, 25 children randomized either to daily Pulmozyme or to normal saline aerosol were evaluated at randomization and at 3 and 12 months. Outcome variables were pulmonary function test (PFT) results, a global HRCT score, and a composite score incorporating PFTs and HRCT scoring. Regression analyses with generalized estimating equations permitted estimation of the difference in treatment effect between groups over time for each outcome. The largest difference in treatment effects observed at 12 months, measured by the percentage change from baseline, were with the composite total and maximal CT/PFT scores (35.4 and 30.4%), compared with mean forced expiratory flow during the middle half of the FVC (FEF25-75%) (13.0%) and total and maximal global HRCT scores (6.2%, 7.2%). The composite total and maximal CT/PFT scores were the most sensitive outcome measures for discriminating a treatment effect in children with cystic fibrosis with normal or mildly reduced pulmonary function during a 1-year trial of Pulmozyme.

    View details for DOI 10.1164/rccm.200209-1093OC

    View details for Web of Science ID 000185039000015

    View details for PubMedID 12746252

  • Active lower gastrointestinal hemorrhage diagnosed by magnetic resonance angiography: case report ABDOMINAL IMAGING Chan, F. P., Chhor, C. M. 2003; 28 (5): 637-639

    Abstract

    Contrast-enhanced magnetic resonance angiography (MRA) has demonstrated the potential for detecting gastrointestinal bleeding in animal studies. We report a case of active lower gastrointestinal bleed diagnosed with MRA in an elderly patient. Clinical, radiologic, and surgical findings are described.

    View details for DOI 10.1007/s00261-003-0017-y

    View details for Web of Science ID 000184936800008

    View details for PubMedID 14628866

  • An automated approach to quantitative air trapping measurements in mild cystic fibrosis CHEST Goris, M. L., Zhu, H. Y., Blankenberg, F., Chan, F., Robinson, T. E. 2003; 123 (5): 1655-1663

    Abstract

    To automatically derive the degree of air trapping in mild cystic fibrosis (CF) disease from high-resolution CT (HRCT) data, and to evaluate the discriminating power of the measurement.The data consist of six pairs of anatomically matched tomographic slices, obtained during breath-holding in triggered HRCT acquisitions. The pairs consist of an inspiratory slice, at > or = 95% of slow vital capacity, and an expiratory slice at near residual volume (nRV). The subjects are 25 patients with mild CF and 10 age-matched, normal control subjects.Lung segmentation is automatic. The limits defining air trapping in the expiratory slices are determined by the distribution of densities in the expanded lung. They are modulated by density changes between expiration and inspiration. Air trapping defects consist of contiguous low-density voxels. The difference between patients and control subjects was evaluated in comparison to pulmonary function test (PFT) results and lung density distribution descriptors (global density descriptors).In mild CF, air trapping does not correlate with global PFT results, except for the ratio of residual volume (RV) to total lung capacity (TLC); however, the size of air trapping defects was the best discriminator between patients and control subjects (p < 0.005). Of PFT results, only RV/TLC reached significance at p < 0.05. The global density descriptors reached near significance in the nRV images only.Air trapping defined as defect size and measured in an objective automated manner is a powerful discriminator for mild CF.

    View details for Web of Science ID 000182773000051

    View details for PubMedID 12740287

  • Time-resolved three-dimensional phase-contrast MRI JOURNAL OF MAGNETIC RESONANCE IMAGING Markl, M., Chan, F. P., Alley, M. T., Wedding, K. L., Draney, M. T., Elkins, C. J., Parker, D. W., Wicker, R., Taylor, C. A., Herfkens, R. J., Pelc, N. J. 2003; 17 (4): 499-506

    Abstract

    To demonstrate the feasibility of a four-dimensional phase contrast (PC) technique that permits spatial and temporal coverage of an entire three-dimensional volume, to quantitatively validate its accuracy against an established time resolved two-dimensional PC technique to explore advantages of the approach with regard to the four-dimensional nature of the data.Time-resolved, three-dimensional anatomical images were generated simultaneously with registered three-directional velocity vector fields. Improvements compared to prior methods include retrospectively gated and respiratory compensated image acquisition, interleaved flow encoding with freely selectable velocity encoding (venc) along each spatial direction, and flexible trade-off between temporal resolution and total acquisition time.The implementation was validated against established two-dimensional PC techniques using a well-defined phantom, and successfully applied in volunteer and patient examinations. Human studies were performed after contrast administration in order to compensate for loss of in-flow enhancement in the four-dimensional approach.Advantages of the four-dimensional approach include the complete spatial and temporal coverage of the cardiovascular region of interest and the ability to obtain high spatial resolution in all three dimensions with higher signal-to-noise ratio compared to two-dimensional methods at the same resolution. In addition, the four-dimensional nature of the data offers a variety of image processing options, such as magnitude and velocity multi-planar reformation, three-directional vector field plots, and velocity profiles mapped onto selected planes of interest.

    View details for DOI 10.1002/jmri.10272

    View details for Web of Science ID 000182453200016

    View details for PubMedID 12655592

  • A comprehensive approach to MR imaging of mesenteric ischemia ABDOMINAL IMAGING Chow, L. C., Chan, F. P., Li, K. C. 2002; 27 (5): 507-516

    View details for DOI 10.1007/s00261-001-0077-9

    View details for Web of Science ID 000177561500003

    View details for PubMedID 12172988

  • In vivo validation of numerical prediction of blood flow in arterial bypass grafts ANNALS OF BIOMEDICAL ENGINEERING Ku, J. P., Draney, M. T., Arko, F. R., Lee, W. A., Chan, F. P., Pelc, N. J., Zarins, C. K., Taylor, C. A. 2002; 30 (6): 743-752

    Abstract

    In planning operations for patients with cardiovascular disease, vascular surgeons rely on their training, past experiences with patients with similar conditions, and diagnostic imaging data. However, variability in patient anatomy and physiology makes it difficult to quantitatively predict the surgical outcome for a specific patient a priori. We have developed a simulation-based medical planning system that utilizes three-dimensional finite-element analysis methods and patient-specific anatomic and physiologic information to predict changes in blood flow resulting from surgical bypass procedures. In order to apply these computational methods, they must be validated against direct experimental measurements. In this study, we compared in vivo flow measurements obtained using magnetic resonance imaging techniques to calculated flow values predicted using our analysis methods in thoraco-thoraco aortic bypass procedures in eight pigs. Predicted average flow rates and flow rate waveforms were compared for two locations. The predicted and measured waveforms had similar shapes and amplitudes, while flow distribution predictions were within 10.6% of the experimental data. The average absolute difference in the bypass-to-inlet blood flow ratio was 5.4 +/- 2.8%. For the aorta-to-inlet blood flow ratio, the average absolute difference was 6.0 +/- 3.3%.

    View details for DOI 10.1114/1.1496086

    View details for Web of Science ID 000177640900001

    View details for PubMedID 12220075

  • Magnetic resonance imaging in the diagnosis and follow up of Takayasu's arteritis in children ANNALS OF THE RHEUMATIC DISEASES Aluquin, V. P., Albano, S. A., Chan, F., Sandborg, C., Pitlick, P. T. 2002; 61 (6): 526-529

    Abstract

    Takayasu's arteritis (TA) has a mortality rate of up to 40% in children. Because the clinical presentation of TA is often non-specific, accurate and prompt diagnosis depends on a high degree of awareness and appropriate laboratory and imaging studies.To examine the use of advanced magnetic resonance imaging (MRI) in evaluating, gauging activity, and following the complications of TA.T1 weighted, T2 weighted, contrast enhanced MR images, and MR angiograms of the chest and abdomen were obtained in three children (age range 11-14 years). The MRI studies confirmed the diagnosis of active TA and were repeated to evaluate response to treatment. Two patients showed complete resolution of lesions found on MRI at six and 12 months' follow up, while the third patient showed no significant improvement.MRI can be used to help establish the initial diagnosis of TA in children, and it can also be used to monitor disease activity and to guide treatment.

    View details for Web of Science ID 000175769200012

    View details for PubMedID 12006326

  • Can a multiphasic contrast-enhanced three-dimensional fast spoiled gradient-recalled echo sequence be sufficient for liver MR imaging? AMERICAN JOURNAL OF ROENTGENOLOGY Coulam, C. H., Chan, F. P., Li, K. C. 2002; 178 (2): 335-341

    Abstract

    The purpose of this study was to determine the accuracy of a multiphasic gadolinium-enhanced three-dimensional (3D) fast spoiled gradient-recalled echo sequence alone in the detection and characterization of focal liver lesions compared with a comprehensive liver evaluation using multiphasic gadolinium-enhanced 3D fast spoiled gradient-recalled echo, T1-weighted, and fat-suppressed fast spin-echo T2-weighted sequences.A retrospective review of abdominal MR imaging examinations in 61 patients was performed. All MR examinations included unenhanced spin-echo T1-weighted, unenhanced fat-suppressed fast spin-echo T2-weighted, and multiphasic gadolinium-enhanced 3D fast spoiled gradient-recalled echo sequences obtained during successive breath-holds. The liver was evaluated for focal lesions first with the 3D spoiled gradient-recalled echo sequences and then, during a separate sitting, with the T1- and T2-weighted sequences. The usefulness of each sequence in the detection and characterization of lesions was recorded. The gold standard for lesion detection and characterization was all three imaging sequences reviewed together.A total of 114 focal liver lesions were identified, 54 of which were simple cysts. The 3D spoiled gradient-recalled echo sequence alone detected 92 (81%) of the 114 lesions, and the T1- and T2-weighted sequences detected 95 (83%) of the 114 lesions. Of the 60 lesions that were not simple cysts, the 3D spoiled gradient-recalled echo sequence alone detected 58 (97%), and T1- and T2-weighted sequences detected 51 (85%). In 24% of the patients with lesions, the T1- and T2-weighted sequences were found to be helpful for the characterization of lesions.A multiphasic contrast-enhanced 3D fast spoiled gradient-recalled echo sequence alone detects most of the clinically relevant focal liver lesions. Additional liver examination using both unenhanced T1- and T2-weighted sequences is helpful for lesion characterization but increases the detection rate only minimally.

    View details for Web of Science ID 000173486500010

    View details for PubMedID 11804888

  • Images in clinical medicine. Paradoxical embolus. New England journal of medicine Chan, F. P., JONES, T. R. 2001; 345 (11): 803-?

    View details for PubMedID 11556300

  • Validation of in vivo MR measurement of oxygen saturation after resuscitation with a hemoglobin-based oxygen carrier in a rabbit model ACADEMIC RADIOLOGY Chan, F. P., Jahr, J. S., Driessen, B., Daunt, D. A., Li, K. C. 2001; 8 (7): 583-590

    Abstract

    The authors tested whether noninvasive magnetic resonance (MR) oximetry is accurate in the in vivo measurement of oxygen saturation in a stroma-free, hemoglobin-based oxygen carrier (HBOC).A central venous catheter was placed in the inferior vena cava (IVC) of 10 New Zealand white rabbits (weight range, 2.5-3.2 kg). Each rabbit underwent removal of 20% of blood volume followed by resuscitation with 10 mL/kg of bovine HBOC-200. Oxygen saturation of the blood mixture was measured in vivo at the IVC with MR oximetry, with separate in vitro calibration for each animal. Blood drawn from the IVC was measured with ex vivo oximetry, which was used as the standard of reference. The in vivo and ex vivo measurements were compared.There was no significant difference (P > .1) between measurements obtained with MR oximetry and ex vivo oximetry. The results with in vivo MR oximetry demonstrated excellent correlation with those from ex vivo oximetry (r = 0.99) over a wide range of physiologic oxygen saturation values (16.7%-74.9%) in venous blood.Noninvasive in vivo MR measurement of oxygen saturation is valid for whole blood mixed with stroma-free hemoglobin. Therefore, MR oximetry may be clinically useful for assessing the oxygenation status in patients resuscitated with a HBOC.

    View details for Web of Science ID 000169561100003

    View details for PubMedID 11450958

  • New approaches to the investigation of focal hepatic lesions BEST PRACTICE & RESEARCH IN CLINICAL GASTROENTEROLOGY Li, K. C., Chan, F. 1999; 13 (4): 529-543

    Abstract

    In the past few years, tremendous advances have been made in the fields of magnetic resonance imaging, computed tomography and ultrasonography. These include the development of novel contrast agents and new approaches to image acquisition and processing. This review provides an overview of the state-of-the-art of imaging investigation of focal hepatic lesions and highlights some of the most exciting emerging technologies.

    View details for Web of Science ID 000084893800004

    View details for PubMedID 10654918

  • A comprehensive approach using MR imaging to diagnose acute segmental mesenteric ischemia in a porcine model AMERICAN JOURNAL OF ROENTGENOLOGY Chan, F. P., Li, K. C., Heiss, S. G., Razavi, M. K. 1999; 173 (3): 523-529

    Abstract

    Acute mesenteric ischemia is a lethal disease that lacks a noninvasive diagnostic test. We evaluated the abilities of contrast-enhanced MR angiography, MR oximetry, and real-time interactive MR imaging to diagnose segmental mesenteric ischemia in a porcine model.Segmental mesenteric ischemia was created by subselective Gelfoam embolization of the mesenteric circulation in eight pigs. Conventional digital subtraction angiography (DSA), MR oximetry, and real-time interactive MR imaging of the small bowel were performed before and after embolization. Changes in the perfusion pattern seen on DSA established the regions of true ischemia. Postembolization DSA and MR angiography were compared with this gold standard.Both MR angiography and DSA had high sensitivity (91% and 100%, respectively) for detecting ischemic regions. The difference was not statistically significant (p > .2). MR angiography yielded lower specificity than DSA (80% and 90%, respectively; p < .01). After embolization, the oxygen saturation in the superior mesenteric vein (SMV) dropped significantly (p < .005). After embolization, the SMV also showed oxygen saturation significantly lower than that in the inferior vena cava (p < .005). In two of the animals, segmental hypomotility of the small bowel was observed.MR oximetry is capable of detecting oxygen desaturation caused by segmental ischemia. A loss of oxygen saturation in the SMV relative to that in the inferior vena cava provides a convenient marker of mesenteric ischemia. Contrast-enhanced MR angiography has sensitivity and specificity approaching those of DSA. Both MR techniques hold promise for the detection of acute mesenteric ischemia.

    View details for Web of Science ID 000082125100002

    View details for PubMedID 10470873

  • EFFECTS OF RF AMPLIFIER DISTORTION ON SELECTIVE EXCITATION AND THEIR CORRECTION BY PREWARPING MAGNETIC RESONANCE IN MEDICINE Chan, F., Pauly, J., Macovski, A. 1992; 23 (2): 224-238

    Abstract

    In a magnetic resonance imaging system, an RF power amplifier is employed to boost an RF pulse to sufficient strength to excite the nuclear spins in a subject. The nonideal behavior of this amplifier distorts a selective-excitation pulse, and this distortion in turn degrades the slice profile. We have found two types of nonideal behavior particularly troublesome: nonlinearity and incidental phase modulation. One of their effects is the introduction of an unwanted "skirt" in the out-of-slice region of a slice profile. We present an effective method of correction in which a selective-excitation pulse is prewarped to compensate for the distortion.

    View details for Web of Science ID A1992HD21300003

    View details for PubMedID 1549038

Conference Proceedings


  • Advances in imaging techniques for the diagnosis of focal hepatic lesions Li, K. C., Chan, F. WILEY-BLACKWELL PUBLISHING, INC. 1999: S22-S27

    Abstract

    In the past few years, tremendous advances have been made in the fields of ultrasound, computed tomography, magnetic resonance imaging and contrast agent development. The purpose of this article is to highlight the important developments in imaging techniques that can be used for detection and characterization of focal hepatic lesions.

    View details for Web of Science ID 000081033600006

    View details for PubMedID 10382634

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