James Carr

University of Texas Southwestern Medical Center, Dallas, Texas, United States

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Publications (242)954.59 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Nonischemic cardiomyopathy is a common cause of left ventricular (LV) dysfunction and myocardial fibrosis. The purpose of this study was to noninvasively evaluate changes in segmental LV extracellular volume (ECV) fraction, LV velocities, myocardial scar, and wall motion in nonischemic cardiomyopathy patients. Cardiac MRI including pre- and postcontrast myocardial T1 mapping and velocity quantification (tissue phase mapping) of the LV (basal, midventricular, and apical short axis) was applied in 31 patients with nonischemic cardiomyopathy (50±18 years). Analysis based on the 16-segment American Heart Association model was used to evaluate the segmental distribution of ECV, peak systolic and diastolic myocardial velocities, scar determined by late gadolinium enhancement, and wall motion abnormalities. LV segments with scar or impaired wall motion were significantly associated with elevated ECV (rs =0.26; P<0.001) and reduced peak systolic radial velocities (r=-0.43; P<0.001). Regional myocardial velocities and ECV were similar for patients with reduced (n=12; ECV=0.28±0.06) and preserved left ventricular ejection fraction (n=19; ECV=0.30±0.09). Patients with preserved left ventricular ejection fraction showed significant relationships between increasing ECV and reduced systolic (r=-0.19; r=-0.30) and diastolic (r=0.34; r=0.26) radial and long-axis peak velocities (P<0.001). Even after excluding myocardial segments with late gadolinium enhancement, significant relationships between ECV and segmental LV velocities were maintained indicating the potential of elevated ECV to identify regional diffuse fibrosis not visible by late gadolinium enhancement, which was associated with impaired regional LV function. Regionally elevated ECV negatively affected myocardial velocities. The association of elevated regional ECV with reduced myocardial velocities independent of left ventricular ejection fraction suggests a structure-function relationship between altered ECV and segmental myocardial function in nonischemic cardiomyopathy. © 2014 American Heart Association, Inc.
    Circulation Cardiovascular Imaging 01/2015; 8(1). · 5.80 Impact Factor
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    ABSTRACT: The aim of the present study was to determine the effects of the latency period on the performance of free-breathing coronary wall MRI. With the approval of IRB, 70 participants were recruited for coronary wall magnetic resonance imaging (MRI) and provided written informed consent. In 35 subjects, right coronary segments (RCA1–3) were imaged first; in the remaining subjects, the left coronary segments (LM and LAD1–3) were imaged first. The images were classified into groups; group 1 contained right coronary images from the subjects whose right coronary segments were imaged first and left coronary images from the subjects whose left coronary segments were imaged first. Group 2 contained the other coronary segments. The image scores (ranked1–3), latency periods, drift of the position of the navigator (NAV), scan efficiency were compared between image groups. Image group 1 has higher scores (1.66 ± 0.55 vs. 1.46 ± 0.51), shorter latency periods (32.04 ± 4.24 vs. 44.22 ± 5.57 min), lower drift in the location of the NAV (1.90 ± 1.27 mm vs. 2.61 ± 1.71 mm) and higher scan efficiency (32.7 ± 7.6 vs. 29.9 ± 7.9 %) than group 2. Long latency periods have a significantly negative impact on the image quality of coronary wall MRI.
    The International Journal of Cardiovascular Imaging 01/2015; · 2.32 Impact Factor
  • AHA Scientific Sessions 2014, Circulation; 11/2014
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    Circulation 11/2014; 130(19):e171. · 14.95 Impact Factor
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    ABSTRACT: Objective We used magnetic resonance imaging (MRI) to study the prevalence and associated clinical characteristics of high-risk plaque (defined as presence of lipid-rich necrotic core [LRNC] and intraplaque hemorrhage) in the superficial femoral arteries (SFA) among people with peripheral artery disease (PAD). Background The prevalence and clinical characteristics associated with high-risk plaque in the SFA are unknown. Methods Three-hundred-three participants with PAD underwent MRI of the proximal SFA using a 1.5 T S platform. Twelve contiguous 2.5 mm cross-sectional images were obtained. Results LRNC was present in 68 (22.4%) participants. Only one had intra-plaque hemorrhage. After adjusting for age and sex, smoking prevalence was higher among adults with LRNC than among those without LRNC (35.9% vs. 21.4%, p = 0.02). Among participants with vs. without LRNC there were no differences in mean percent lumen area (31% vs. 33%, p = 0.42), normalized mean wall area (0.71 vs. 0.70, p = 0.67) or maximum wall area (0.96 vs. 0.92, p = 0.54) in the SFA. Among participants with LRNC, cross-sectional images containing LRNC had a smaller percent lumen area (33% ± 1% vs. 39% ± 1%, p < 0.001), greater normalized mean wall thickness (0.25 ± 0.01 vs. 0.22 ± 0.01, p < 0.001), and greater normalized maximum wall thickness (0.41 ± 0.01 vs. 0.31 ± 0.01, p < 0.001), compared to cross-sectional images without LRNC. Conclusions Fewer than 25% of adults with PAD had high-risk plaque in the proximal SFA using MRI. Smoking was the only clinical characteristic associated with presence of LRNC. Further study is needed to determine the prognostic significance of LRNC in the SFA. Clinical trial registration—URL http://www.clinicaltrials.gov. Unique identifier: NCT00520312.
    Atherosclerosis 11/2014; 237(1):169–176. · 3.71 Impact Factor
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    ABSTRACT: We used magnetic resonance imaging (MRI) to study the prevalence and associated clinical characteristics of high-risk plaque (defined as presence of lipid-rich necrotic core [LRNC] and intraplaque hemorrhage) in the superficial femoral arteries (SFA) among people with peripheral artery disease (PAD).
    Atherosclerosis 09/2014; 237(1):169-176. · 3.71 Impact Factor
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    ABSTRACT: PurposeTo test the feasibility of velocity distribution analysis for identifying altered three-dimensional (3D) flow characteristics in patients with aortic disease based on 4D flow MRI volumetric analysis.Methods Forty patients with aortic (Ao) dilation (mid ascending aortic diameter MAA = 40 ± 7 mm, age = 56 ± 17 years, 11 females) underwent cardiovascular MRI. Four groups were retrospectively defined: mild Ao dilation (n = 10; MAA < 35 mm); moderate Ao dilation (n = 10; 35 < MAA < 45 mm); severe Ao dilation (n = 10; MAA > 45 mm); Ao dilation+aortic stenosis AS (n = 10; MAA > 35 mm and peak velocity > 2.5 m/s). The 3D PC-MR angiograms were computed and used to obtain a 3D segmentation of the aorta which was divided into four segments: root, ascending aorta, arch, descending aorta. Radial chart displays were used to visualize multiple parameters representing segmental changes in the 3D velocity distribution associated with aortic disease.ResultsChanges in the velocity field and geometry between cohorts resulted in distinct hemodynamic patterns for each aortic segment. Disease progression from mild to Ao dilation + AS resulted in significant differences (P < 0.05) in flow parameters across cohorts and increased radial chart size for root and ascending aorta segments by 146% and 99%, respectively.Conclusion Volumetric 4D velocity distribution analysis has the potential to identify characteristic changes in regional blood flow patterns in patients with aortic disease. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 09/2014; · 3.40 Impact Factor
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    ABSTRACT: There exists considerable controversy surrounding the timing and extent of aortic resection for patients with BAV disease. Since abnormal wall shear stress (WSS) is potentially associated with tissue remodeling in BAV-related aortopathy, we propose a methodology that creates patient-specific 'heat maps' of abnormal WSS, based on 4D flow MRI. The heat maps were created by detecting outlier measurements from a volumetric 3D map of ensemble-averaged WSS in healthy controls. 4D flow MRI was performed in 13 BAV patients, referred for aortic resection and 10 age-matched controls. Systolic WSS was calculated from this data, and an ensemble-average and standard deviation (SD) WSS map of the controls was created. Regions of the individual WSS maps of the BAV patients that showed a higher WSS than the mean + 1.96SD of the ensemble-average control WSS map were highlighted. Elevated WSS was found on the greater ascending aorta (35% ± 15 of the surface area), which correlated significantly with peak systolic velocity (R (2) = 0.5, p = 0.01) and showed good agreement with the resected aortic regions. This novel approach to characterize regional aortic WSS may allow clinicians to gain unique insights regarding the heterogeneous expression of aortopathy and may be leveraged to guide patient-specific resection strategies for aorta repair.
    Annals of Biomedical Engineering 08/2014; · 3.23 Impact Factor
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    ABSTRACT: The left ventricular outflow tract (LVOT) peak pressure gradient is an important haemodynamic descriptor in patients with hypertrophic cardiomyopathy (HCM); however, secondary alterations in aortic blood flow have not been well described in these patients. Aortic flow derangement is not easily assessed by traditional imaging methods, but may provide unique characterization of this disease. In this study, we demonstrated how four-dimensional (4D) flow MRI can assess LVOT peak pressure gradients in HCM patients and also evaluated the ascending aorta (AAo) haemodynamic derangement associated with HCM.
    European Heart Journal – Cardiovascular Imaging 08/2014; · 2.65 Impact Factor
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    ABSTRACT: We sought to evaluate the feasibility of k-t parallel imaging for accelerated 4D flow MRI in the hepatic vascular system by investigating the impact of different acceleration factors.
    Magma (New York, N.Y.). 08/2014;
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    ABSTRACT: Associations of collateral vessels and lower extremity plaque with functional decline are unknown. Among people with peripheral artery disease (PAD), we determined whether greater superficial femoral artery (SFA) plaque burden combined with fewer lower extremity collateral vessels was associated with faster functional decline, compared to less plaque and/or more numerous collateral vessels. A total of 226 participants with ankle-brachial index (ABI) <1.00 underwent magnetic resonance imaging of lower extremity collateral vessels and cross-sectional imaging of the proximal SFA. Participants were categorized as follows: Group 1 (best), maximum plaque area < median and collateral vessel number ≥6 (median); Group 2, maximum plaque area < median and collateral vessel number <6; Group 3, maximum plaque area > median and collateral vessel number ≥6; Group 4 (worst), maximum plaque area > median and collateral vessel number <6. Functional measures were performed at baseline and annually for 2 years. Analyses adjust for age, sex, race, comorbidities, and other confounders. Annual changes in usual-paced walking velocity were: Group 1, +0.01 m/s; Group 2, -0.02 m/s; Group 3, -0.01 m/s; Group 4, -0.05 m/s (p-trend=0.008). Group 4 had greater decline than Group 1 (p<0.001), Group 2 (p=0.029), and Group 3 (p=0.010). Similar trends were observed for fastest-paced 4-meter walking velocity (p-trend=0.018). Results were not substantially changed when analyses were repeated with additional adjustment for ABI. However, there were no associations of SFA plaque burden and collateral vessel number with decline in 6-minute walk. In summary, a larger SFA plaque burden combined with fewer collateral vessels is associated with a faster decline in usual and fastest-paced walking velocity in PAD.
    Vascular Medicine 07/2014; 19(4):281-288. · 1.73 Impact Factor
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    ABSTRACT: Paradoxical embolization is frequently posited as a mechanism of ischemic stroke in patients with patent foramen ovale. Several studies have suggested that the deep lower extremity and pelvic veins might be an embolic source in cryptogenic stroke (CS) patients with patent foramen ovale.
    Stroke 06/2014; 45(8). · 6.02 Impact Factor
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    ABSTRACT: To test the hypothesis that biomechanical changes are quantitatively related to morphological features of coronary arteries in heart transplant (HTx) recipients.
    European Journal of Radiology 05/2014; · 2.16 Impact Factor
  • Annual Meeting ISMRM-ESMRMB, Milan; 05/2014
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    ABSTRACT: The objective of this study was to evaluate the potential of 4D flow MRI to assess valve effective orifice area (EOA) in patients with aortic stenosis as determined by the jet shear layer detection (JSLD) method.
    Magnetic Resonance Imaging 04/2014; · 2.02 Impact Factor
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    ABSTRACT: OBJECTIVE. The objective of our study was to assess the diagnostic performance of quiescent-interval single-shot (QISS) MR angiography (MRA) at 3 T for the evaluation of chronic lower limb ischemia. SUBJECTS AND METHODS. For this prospective study, 25 patients referred for lower extremity angiography for suspected or known chronic peripheral arterial disease were imaged on a 3-T system using QISS MRA. Contrast-enhanced MRA of the lower extremities was acquired at 3 T for each patient at the time of the initial visit and served as the noninvasive reference standard. Two blinded reviewers separately graded the degree of arterial stenosis. The sensitivity and specificity of QISS MRA for the determination of significant (≥ 50%) stenosis were calculated against contrast-enhanced MRA. Subsequent selective digital subtraction angiography (DSA) was performed and reviewed in nine patients. RESULTS. QISS MRA exhibited diagnostic performance nearly equivalent to that of contrast-enhanced MRA and also showed strong correlation with findings on DSA. Segment-based analysis revealed that, for the two reviewers, QISS MRA had sensitivities of 95.9% (142 of 148 segments) and 93.5% (145 of 155 segments) and specificities of 98.5% (595 of 604 segments) and 97.0% (578 of 596 segments) on comparison with contrast-enhanced MRA. CONCLUSION. QISS MRA maintains high diagnostic performance at 3 T despite the challenges inherent to image acquisition at higher field strengths.
    American Journal of Roentgenology 04/2014; 202(4):886-93. · 2.74 Impact Factor
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    ABSTRACT: PurposeTo compute cohort-averaged wall shear stress (WSS) maps in the thoracic aorta of patients with aortic dilatation or valvular stenosis and to detect abnormal regional WSS.Methods Systolic WSS vectors, estimated from four-dimensional flow MRI data, were calculated along the thoracic aorta lumen in 10 controls, 10 patients with dilated aortas, and 10 patients with aortic valve stenosis. Three-dimensional segmentations of each aorta were coregistered by group and used to create a cohort-specific aortic geometry. The WSS vectors of each subject were interpolated onto the corresponding cohort-specific geometry to create cohort-averaged WSS maps. A Wilcoxon rank sum test was used to generate aortic P-value maps (P<0.05) representing regional relative WSS differences between groups.ResultsCohort-averaged systolic WSS maps and P-value maps were successfully created for all cohorts and comparisons. The dilation cohort showed significantly lower WSS on 7% of the ascending aorta surface, whereas the stenosis cohort showed significantly higher WSS on 34% of the ascending aorta surface.Conclusions The findings of this study demonstrated the feasibility of generating cohort-averaged WSS maps for the visualization and identification of regionally altered WSS in the presence of disease, compared with healthy controls. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 04/2014; · 3.40 Impact Factor
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    ABSTRACT: The objective of this study was to assess the evolution of T1 contrast (T1c) between cardiovascular tissues, contrast agents, and magnetic field strengths. This Health Insurance Portability and Accountability Act-compliant study was approved by the institutional review board, and written informed consent was obtained from all participants. Eight healthy volunteers were recruited to undergo 4 consecutive magnetic resonance (MR) scans with the same imaging parameters. Scans 1 and 2 were performed using a 3-T MR scanner, and scans 3 and 4 were performed using a 1.5-T MR scanner. Gadofosveset trisodium (0.03 mmol/kg) was injected for scans 1 and 3, and gadopentetate dimeglumine (Gd-DTPA) (0.1 mmol/kg) was used for scans 2 and 4. Modified Look-Locker inversion recovery T1 maps with a midventricular short-axis view were acquired before contrast and repeated every 5 minutes until 45 minutes after contrast agent administration. T1 contrast tissue (T1myocardium - T1blood), T1c agent (T1Gd-DTPA - T1Gadofosveset), and T1c field (T13T - T11.5T) were calculated and compared using t tests. The T1c tissue of the 3-T scanner was larger than that of the 1.5-T scanner for both contrast agents. In both the myocardium and the blood pool, the T1c agent of the 1.5-T scanner was larger than that of the 3-T scanner. Gadofosveset trisodium exhibited a larger T1c field and T1c tissue than did Gd-DTPA. The T1c tissue induced by Gd-DTPA diminished faster than that induced by gadofosveset trisodium at both 1.5 and 3 T. Our study demonstrates the independent effects of timing, contrast agent type, and magnetic field strength on postcontrast T1c under general physiological conditions. The behaviors of T1c can be used to tailor quantitative MR imaging protocols for various clinical purposes.
    Investigative radiology 01/2014; · 4.85 Impact Factor
  • SCMR; 01/2014
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    ABSTRACT: Purpose: Patients with aortic dilation often exhibit eccentric transvalvular flow jets. The angle of the flow jet from the aorta centerline, or the flow jet angle (FJA), has been reported as a risk factor for aortic dilation in bicuspid aortic valve patients 1 . In recent studies, we introduced a jet shear layer detection (JSLD) method for the automated characterization of the transvalvular flow structure across the aortic valve 2,3 . The objective of this study was to develop and apply a new algorithm for the semiautomatic evaluation of FJA using a 3D JSLD structure based on 4D flow MRI data. Results in 30 patients with aortic dilation and varying degrees of aortic valve stenosis were compared to the manual calculation of flow angle using 2D analysis planes placed at the site of the vena contracta. Methods: 30 patients with aortic dilation and tricuspid aortic valves (age=56±17 years, female=7) were identified via retrospective chart review and IRB approval. The mid-ascending aorta (MAA) diameter was used to assess aortic (Ao) dilation and the presence of aortic valve stenosis was assessed with transvalvular peak velocity (PV). Patients were classified into three groups: Controls (MAA<35 mm and PV<1.5 m/s); Ao Dilation (MAA>35 mm and PV<1.5 m/s); Ao Dilation+Stenosis (MAA>35 mm and PV>1.5 m/s). 4D flow MRI was performed at 1.5T and 3T with full volumetric coverage of the thoracic aorta in a sagittal oblique 3D slab (spatial resolution=2.5×2.1×3.2 mm 3 ; temporal resolution=40-50 ms) using prospective ECG gating and a respiratory navigator placed on the lung-liver interface. Pulse sequence parameters were as follows: 1.5 T scan parameters ranged from TE/TR=2.3–3.4/4.8–6.6 ms, flip angle α=7–15° and the field of view was 340–400×200–300 mm; 3 T scans used TE/TR =2.5/5.1 ms, flip angle α=7–15°, and the field of view was 400×308 mm. 4D flow data were used to compute a 3D PC-MRA which allowed for 3D segmentation of the aorta (Mimics, Materialise, Leuven, Belgium). The segmented aorta was used to calculate: the vessel centerline, a masked velocity field, and the 3D JSLD structure (Matlab, Natick, MA, USA). The 3D JSLD structure was obtained from the peak systolic velocity field, V, by ∇(ωΛV) (where ω is the vorticity calculated by a Richardson interpolation scheme) and used to detect the post-valve jet-flow zone, i.e. vena contracta 2, 4 . A centerline segment at the vena contracta was used to obtain a centerline vector and the 3D JSLD structure center of mass vector. Both vectors were then used to estimate FJA (Fig. 1B). A workflow schematic for the 3D JSLD method is shown in Fig. 1C. For reference values, the manual FJA was calculated using 2D planes hand-positioned at the vena contracta (immediately downstream from the aortic valve, Fig. 1B). Both methods were compared by linear regression and Bland-Altman analysis with the 2D FJA as the reference. Results and Discussion: Patient characteristics are summarized in Table 1. A significant difference between Ao Dilation and Ao Dilation+Stenosis vs. Control was observed for age (p<0.05) and MAA (p<0.001). The ejection fraction was higher in Ao Dilation (p<0.05 vs. Control). Bland-Altman analysis (Fig. 2A) showed that difference between 2D velocity and 3D JSLD FJA increases with MAA diameter and valve stenosis. The FJA derived from 3D JSLD and 2D planar analysis were significantly different between Ao Dilation and Ao Dilation+Stenosis, as compared to Controls (p<0.05, Fig. 2B). Noticeably, the 3D JSLD FJA method detected significant differences between stenotic vs. non-stenotic Ao dilatation (p<0.001) while planar FJA analysis did not. A higher FJA was most likely found in Ao Dilation+Stenosis due to the presence of a larger MAA and a higher degree of valvular obstruction. A significant relationship was found between PV and 3D JSLD FJA (r=0.515, p<0.05), suggesting a relationship of FJA and aortic stenosis severity. The 3D JSLD FJA method detected differences between stenotic and non-stenotic Ao dilation groups, while the 2D method did not. Manual interaction while placing 2D analysis planes may have increased measurement noise. The decreased user interaction required for the 3D JSLD method may reduce measurement noise and enable stratification of flow angle differences between the stenotic and non-stenotic Ao dilation groups. Previous studies suggest that flow jet impingement on the convexity aortic area may led to wall remodeling (i.e. aortic dilation) 5 . Although this is a cross-sectional study and longitudinal outcomes were not examined, it is important to note the positive correlation between aortic dilation and FJA. Furthermore, FJA was observed to be closely related to valve hemodynamics (i.e. PV). This is important given recent findings that FJA is associated with aortic stenosis severity and left ventricle remodeling 6 . Thus, FJA is important to investigate for a relationship to aortic wall remodeling and valve and left ventricle function. These findings highlight a potential application of the JSLD FJA algorithm. Conclusion: The assessment of FJA can be automated using the volumetric 3D JSLD structure and the aorta centerline using data from 4D flow MRI exams. Using this technique, the FJA was found to be significantly higher in patients with severe aortic dilation and aortic valve stenosis. Future longitudinal studies are needed to evaluate the impact of FJA on the progression of aortic dilation.: Flow jet angle estimation using 4D flow data and jet shear layer detection method. A) Velocity streamlines inside the 3D segmentation of the aorta (segmentation obtained from the 3D PC-MRA). The black box indicates the region magnified in 'B'. B) Dashed lines indicate the level of the left ventricle outflow tract (LVOT) and vena contracta (AoVC). The AoVC plane was used to estimate the 2D flow jet angle. Jet shear layer detection (JSLD) was computed from the full 4D flow dataset. The resulting lateral view of the 3D JSLD structure (red volume) and volume centerline (black) is shown. The centerline vector (yellow arrow) and 3D JSLD center of mass vector (green arrow) determine the jet flow angle. C) Workflow schematic for the computation of the 3D JSLD jet angle.
    Proc. Intl. Soc. Mag. Reson. Med.; 01/2014

Publication Stats

2k Citations
954.59 Total Impact Points

Institutions

  • 2014
    • University of Texas Southwestern Medical Center
      Dallas, Texas, United States
  • 2001–2014
    • Northwestern University
      • Department of Radiology
      Evanston, Illinois, United States
    • Saint Vincent Hospital
      Worcester, Massachusetts, United States
    • Washington University in St. Louis
      San Luis, Missouri, United States
  • 2013
    • University of Freiburg
      Freiburg, Baden-Württemberg, Germany
  • 2007–2013
    • University of Illinois at Chicago
      Chicago, Illinois, United States
  • 2002–2013
    • Northwestern Memorial Hospital
      • Department of Radiology
      Chicago, Illinois, United States
    • University of Tuebingen
      • Department of Internal Medicine
      Tübingen, Baden-Wuerttemberg, Germany
  • 2012
    • Children's Memorial Hospital
      Chicago, Illinois, United States
  • 2011
    • NorthShore University HealthSystem
      • Department of Radiology
      Chicago, IL, United States
    • Cedars-Sinai Medical Center
      • Cedars Sinai Medical Center
      Los Angeles, California, United States
    • Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center
      Torrance, California, United States
  • 2008
    • University of Chicago
      Chicago, Illinois, United States