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Purpose: To evaluate the feasibility of a proposed cardiorespiratory-resolved analysis in left ventricular (LV) function quantification from real-time cines in a cohort of cardiac patients.Materials and Methods: Electrocardiograph (ECG)-free free-breathing real-time cine imaging based on the balanced steady-state free precession technique was performed on short-axis slices of 20 cardiac patients at 3T. K-means cluster segmentation was used to delineate the endocardial contours, from which the LV centroid and cavity area were determined. Respiratory and cardiac signals were respectively resolved from the filtered LV centroid displacement and time-varied LV cavity area to identify end-expiratory end-diastolic (ED) and end-systolic (ES) images. The obtained LV cavity areas and derived volumetric function indices, including ED volume (EDV), ES volume (ESV), stroke volume (SV), and ejection fraction (EF), were compared with those measured from manual analysis using two-tailed paired Student's t-tests, linear regression analyses, and Bland-Altman plots. Interobserver variability was calculated.Results: The LV cavity area was strongly correlated between the proposed and conventional manual methods (r > 0.87) for three representative slices at the base, middle ventricle, and apex. The average differences between the two methods were 0.66 ± 3.22 mL for EDV, -0.02 ± 2.68 mL for ESV, 0.67 ± 3.73 mL for SV, and 0.17 ± 2.30% for EF. All paired measures exhibited strong correlations (r > 0.96) without significant differences (P = 0.38-0.98). Acceptable interobserver variability (0.19-3.55%) and strong correlations (r > 0.96) were shown for all measures between the two observers.Conclusion: The proposed method is feasible for efficient measurement of LV function from real-time cines.Level Of Evidence: 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:905-914. [ABSTRACT FROM AUTHOR]

Purpose: Carotid artery diseases due to plaque buildup at the carotid bifurcation are a leading cause of stroke. Accurate plaque quantification and characterization of plaque composition and morphology by magnetic resonance imaging(MRI) is essential to identifying high-risk patients. Difficulties in detecting plaque, which is physically small, and the unique physiological structure of the carotid artery make use of a radio frequency (RF) coil array with high resolution, large longitudinal coverage, and deep penetration ideal for clinical examinations. The goal of this project was to design and fabricate a sensitive RF coil array with sufficient imaging coverage and signal-to-noise ratio(SNR) for carotid arteryimaging at 3 T. Methods: Based on clinical requirements and the anatomical structure of the human carotid artery, an 8-channel carotid coil array was designed and fabricated for 3 T MRI of the carotid artery in humans. The performance of the proposed 8-channel carotid coil array was validated through bench tests and MR imaging experiments on a 3 T whole body MRI scanner. Its performance was also compared experimentally to the performance of a commercial 4-channel phased array carotid coil designed by Machnet BV (Machnet BV coil, Roden, Netherlands). Results: The 8-channel carotid coil array performed significantly better in imaging the carotid artery than the commercial 4-channel Machnet BV coil in terms of the SNR, coverage, and penetration depth. In parallel imaging, the proposed 8-channel carotid coil array demonstrated a much lower maximum value and average value of the geometry factor in the region of interest. Carotid arteryimages acquired in vivo using the proposed 8-channel carotid arterycoil and the commercial 4-channel Machnet BV coil were also compared, demonstrating the former's potential for clinical diagnosis. Conclusions: Based on the analyses of phantom and in vivoimaging studies, the proposed 8-channel carotid coil array has the potential for use in clinical diagnosis, performing better in terms of SNR,imaging coverage, and penetration depth than the commercial 4-channel carotid arterycoil array at 3 T. In future studies, the proposed 8-channel carotid coil array can also serve as an important part of a large-scale multichannel coil array for imaging the whole carotid artery system, including the extracranial and intracranial arteries. [ABSTRACT FROM AUTHOR]

Background: To develop and assess an efficient method to identify end-expiratory end-diastolic (ED) and end-systolic (ES) images for accurate quantification of left ventricular (LV) function in real-time cine imaging.Methods: ECG-free free-breathing real-time cine imaging was performed on short-axis slices of thirteen healthy volunteers at 3 Tesla. K-means cluster segmentation was applied to delineate the endocardial contour, from which the LV centroid and cavity area were determined in each cine image. LV centroid displacement along the superior-inferior direction was filtered to extract respiratory motion in each slice. End-expiratory ED and ES images were then identified and used for LV function quantification. Accuracy was evaluated with that measured from the slice-matched standard ECG-gated breathhold segmented cines using two-tail paired Student's t-tests, linear regression analyses and Bland-Altman plots. Intra- and interobserver variability was calculated for each imaging technique.Results: Qualitatively, end-expiratory ED and ES images identified with the proposed method agreed with those determined by frame-by-frame visual inspection in 97.5% of cases (P > 0.05). Quantitatively, good agreement of LV function indices between the real-time cine and the standard segmented cine was observed with averaged differences of 0.1 ± 0.9 g for myocardium mass, -0.3 ± 1.0 mL for ED volume, 0.2 ± 1.2 mL for ES volume, -0.2 ± 1.3 mL for stroke volume, and -0.3 ± 0.8% for ejection fraction. Paired LV function values exhibited strong correlation (r ≥ 0.96) and no significant difference (P > 0.05). The real-time cine and the standard segmented cine showed similar intra- (1.2-3.3% and 1.1-2.8%, respectively) and interobserver variability (2.6-6.9% and 1.8-4.8%, respectively) with all P-values > 0.05. All the variability was comparable with published results.Conclusion: Compared with the laborious frame-by-frame visual inspection, as conventionally adopted, the proposed method is efficient in analyzing real-time cines for the accurate quantification of LV function without excessively manual interactions. [ABSTRACT FROM AUTHOR]

Phase-contrast magnetic resonance imaging (PC-MRI) is used routinely to measure fluid and tissue velocity with a variety of clinical applications. Phase-contrast magnetic resonance imaging methods require acquisition of additional data to enable phase difference reconstruction, making real-time imaging problematic. Shared Velocity Encoding (SVE), a method devised to improve the effective temporal resolution of phase-contrast magnetic resonance imaging, was implemented in a real-time pulse sequence with segmented echo planar readout. The effect of SVE on peak velocity measurement was investigated in computer simulation, and peak velocities and total flow were measured in a flow phantom and in volunteers and compared with a conventional ECG-triggered, segmented k-space phase-contrast sequence as a reference standard. Computer simulation showed a 36% reduction in peak velocity error from 8.8 to 5.6% with SVE. A similar reduction of 40% in peak velocity error was shown in a pulsatile flow phantom. In the phantom and volunteers, volume flow did not differ significantly when measured with or without SVE. Peak velocity measurements made in the volunteers using SVE showed a higher concordance correlation (0.96) with the reference standard than non-SVE (0.87). The improvement in effective temporal resolution with SVE reconstruction has a positive impact on the precision and accuracy of real-time phase-contrast magnetic resonance imaging peak velocity measurements. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the use of a T2-weighted SPACE sequence (T2w-SPACE) to assess carotid stenosis via several methods and compare its performance with contrast-enhanced magnetic resonance angiography (ceMRA). Materials and Methods: Fifteen patients with carotid atherosclerosis underwent dark blood (DB)-MRI using a 3D turbo spin echo with variable flip angles sequence (T2w-SPACE) and ceMRA. Images were coregistered and evaluated by two observers. Comparisons were made for luminal diameter, luminal area, degree of luminal stenosis (NASCET: North American Symptomatic Endarterectomy Trial; ECST: European Carotid Surgery Trial, and area stenosis), and vessel wall area. Degree of NASCET stenosis was clinically classified as mild (<50%), moderate (50%-69%), or severe (>69%). Results: Excellent agreement was seen between ceMRA and T2w-SPACE and between observers for assessment of lumen diameter, lumen area, vessel wall area, and degree of NASCET stenosis ( r > 0.80, P < 0.001). ECST stenosis was consistently higher than NASCET stenosis (48 ± 14% vs. 24 ± 22%, P < 0.001). Area stenosis (72 ± 2%) was significantly higher ( P < 0.001) than both ESCT and NASCET stenosis. Conclusion: DB-MRI of carotid arteries using T2w-SPACE is clinically feasible. It provides accurate measurements of lumen size and degree of stenosis in comparison with ceMRA and offers a more reproducible measure of ECST stenosis than ceMRA. J. Magn. Reson. Imaging 2012;449-455. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effectiveness of flow-sensitive dephasing (FSD) magnetization preparation in improving blood signal suppression of three-dimensional (3D) turbo spin-echo (TSE) sequence (SPACE) for isotropic high-spatial-resolution carotid arterial wall imaging at 3T. Materials and Methods: The FSD-prepared SPACE sequence (FSD-SPACE) was implemented by adding two identical FSD gradient pulses right before and after the first refocusing 180°-pulse of the SPACE sequence in all three orthogonal directions. Nine healthy volunteers were imaged at 3T with SPACE, FSD-SPACE, and multislice T2-weighted 2D TSE coupled with saturation band (SB-TSE). Apparent carotid wall-lumen contrast-to-noise ratio (aCNRw-l) and apparent lumen area (aLA) at the locations with residual-blood (rb) signal shown on SPACE images were compared between SPACE and FSD-SPACE. Carotid aCNRw-l and lumen (LA) and wall area (WA) measured from FSD-SPACE were compared to those measured from SB-TSE. Results: Plaque-mimicking flow artifacts identified in seven carotids on SPACE images were eliminated on FSD-SPACE images. The FSD preparation resulted in slightly reduced aCNRw-l ( P = 0.025), but significantly improved aCNR between the wall and rb regions ( P < 0.001) and larger aLA ( P < 0.001). Compared to SB-TSE, FSD-SPACE offered comparable aCNRw-l with much higher spatial resolution, shorter imaging time, and larger artery coverage. The LA and WA measurements from the two techniques were in good agreement based on intraclasss correlation coefficient (0.988 and 0.949, respectively; P < 0.001) and Bland-Altman analyses. Conclusion: FSD-SPACE is a time-efficient 3D imaging technique for carotid arterial wall with superior spatial resolution and blood signal suppression. J. Magn. Reson. Imaging 2010;31:645-654. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Accurate measurement of spatially variant noise in MR images acquired using parallel imaging techniques is challenging. Image-based noise measurement methods such as the subtraction method proposed by the National Electrical Manufacturers Association or the multiple acquisition method often cannot be applied in vivo due to motion and/or dynamic contrast changes. Based on the Karhunen-Loeve transform and random matrix theory, we propose a novel method to accurately assess the noise variance in image series bearing temporal redundancy. The method fits the probability density function of eigenvalues from the temporal covariance matrix of the image series to the Marcenko-Pastur distribution. The accuracy of our method was validated using numerical simulation and an MR noise measurement experiment. The ability of this method to derive the g-factor map of a static phantom was validated against the multiple acquisition method. The method was applied to in vivo cardiac and brain image series and the results agreed with subtraction and multiple acquisition methods, respectively. This new image-based noise measurement method provides a practical means of retrospectively evaluating the noise level and/or g-factor map from multiframe image series. Magn Reson Med 63:782-789, 2010 © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the feasibility of the dark blood fast spin echo (FSE) T1-weighted-Sampling Perfection with Application of optimized Contrasts using different flip angle Evolution (T1w-SPACE) sequence in assessing whole body arterial wall information from the extracranial carotids to the popliteal artery. Materials and Methods: Twenty-eight subjects were subjected to noncontrast, dark blood whole body magnetic resonance angiography (DB-WBMRA) using a T1w-SPACE sequence optimized for each of the individual stations: carotid artery, thoracic aorta, abdominal aorta, and thigh/superficial femoral artery (SFA). Image quality/vessel wall visualization and the time required to image the four stations were evaluated. Two observers checked the reproducibility of vessel wall depiction by performing quantitative measurements in registered initial and repeat studies (six subjects) of vessel wall and lumen area at 17 locations along the arterial tree. Results: In 25 of the 28 scanned subjects, dark blood arterial images acquired in approximately 1 hour total imaging time allowed whole body arterial vessel wall visualization. Quantitative measurements showed high correlation between the initial and repeat studies for each of the observers as well as high interobserver reproducibility (r > 0.95; P < 0.01). Conclusion: DB-WBMRA using T1w-SPACE is feasible and can be performed with a high degree of reliability. J. Magn. Reson. Imaging 2010; 31: 502-509. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose To evaluate the feasibility of a multi-station three dimensional (3D) T1-weighted turbo spin echo (TSE) dark-blood Sampling Perfection with Application optimized Contrasts using different flip angle Evolution sequence (T1w-SPACE), to assess aorta, iliac, and superficial femoral (SFA) arteries (inflow vessels) by comparing it with a multi-station contrast enhanced MR angiography (CE-MRA) with identical resolution. Materials and Methods A total of 6 volunteers and 14 peripheral arterial disease (PAD) patients were included in the study. Abdominal and thigh T1w-SPACE and lower leg time-resolved MRA (TR-MRA) with low dose contrast were followed by 3-station CE-MRA. Quantitative measurements of lumen area at 17 locations from T1w-SPACE and CE-MRA were obtained. Additionally, vessel wall areas at the same locations were obtained from the T1w-SPACE images. Results Quantitative comparison of lumen areas with T1w-SPACE and CE-MRA revealed strong correlation between the two techniques and strong inter-observer agreement for each of the two imaging methods (r > 0.9; P < 0.001). Localized vessel wall area measurements obtained in PAD patients were significantly greater compared with those obtained in normal volunteers (mean difference 43.75 ± 12.46 mm2; P < 0.001). Stenosis severity obtained from T1w-SPACE localized measurements showed significant arterial area stenosis in PAD patients. Conclusion T1w-SPACE imaging of inflow vessels is feasible, and in addition to CE-MRA has the ability to assess atherosclerotic plaque and vascular remodeling. J. Magn. Reson. Imaging 2009;30:785-793. © 2009 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose To compare two multislice turbo spin-echo (TSE) carotid artery wall imaging techniques at 1.5 T and 3.0 T, and to investigate the feasibility of higher spatial resolution carotid artery wall imaging at 3.0 T. Materials and Methods Multislice proton density-weighted (PDW), T2-weighted (T2W), and T1-weighted (T1W) inflow/outflow saturation band (IOSB) and rapid extended coverage double inversion-recovery (REX-DIR) TSE carotid artery wall imaging was performed on six healthy volunteers at 1.5 T and 3.0 T using time-, coverage-, and spatial resolution-matched (0.47 × 0.47 × 3 mm3) imaging protocols. To investigate whether improved signal-to-noise ratio (SNR) at 3.0 T could allow for improved spatial resolution, higher spatial resolution imaging (0.31 × 0.31 × 3 mm3) was performed at 3.0 T. Carotid artery wall SNR, carotid lumen SNR, and wall-lumen contrast-to-noise ratio (CNR) were measured. Results Signal gain at 3.0 T relative to 1.5 T was observed for carotid artery wall SNR (223%) and wall-lumen CNR (255%) in all acquisitions ( P < 0.025). IOSB and REX-DIR images were found to have different levels of SNR and CNR ( P < 0.05) with IOSB values observed to be larger. Normalized to a common imaging time, the higher spatial resolution imaging at 3.0 T and the lower spatial resolution imaging at 1.5 T provided similar levels of wall-lumen CNR ( P = NS). Conclusion Multislice carotid wall imaging at 3.0 T with IOSB and REX-DIR benefits from improved SNR and CNR relative to 1.5 T, and allows for higher spatial resolution carotid artery wall imaging. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose: To develop and test a delayed-enhancement imaging method for improving the contrast between myocardial infarction (MI) and blood pool.Materials and Methods: The T(2) of blood is significantly longer than that of acute or chronic MI. The proposed multi-contrast delayed-enhancement (MCODE) imaging method produces a series of images with both T(1) and T(2) weightings, which provides both excellent contrast between normal and infarcted myocardium, and between blood and MI.Results: The subendocardial border between MI and blood pool was easily discriminated in the T(2)-weighted image. The measured MI-to-blood contrast-to-noise ratio (CNR) was better in the T(2)-weighted image than in the T(1)-weighted image (22.5+/-8.7 vs. 2.9+/-3.1, mean+/-SD, N=11, P<0.001, for True FISP, and 19.4+/-10.8 vs. 3.9+/-2.3, N=11, P<0.001, for Turbo FLASH).Conclusion: The MCODE method provides a significant improvement in the ability to easily discriminate subendocardial MI by providing a T(2)-weighted image with high contrast between blood and MI. MCODE should improve both the detection and accurate sizing of MI. [ABSTRACT FROM AUTHOR]

Purpose To develop and test a delayed-enhancement imaging method for improving the contrast between myocardial infarction (MI) and blood pool. Materials and Methods The T2 of blood is significantly longer than that of acute or chronic MI. The proposed multicontrast delayed-enhancement (MCODE) imaging method produces a series of images with both T1 and T2 weightings, which provides both excellent contrast between normal and infarcted myocardium, and between blood and MI. Results The subendocardial border between MI and blood pool was easily discriminated in the T2-weighted image. The measured MI-to-blood contrast-to-noise ratio (CNR) was better in the T2-weighted image than in the T1-weighted image (22.5 ± 8.7 vs. 2.9 ± 3.1, mean ± SD, N = 11, P < 0.001, for TrueFISP, and 19.4 ± 10.8 vs. 3.9 ± 2.3, N = 11, P < 0.001, for TurboFLASH). Conclusion The MCODE method provides a significant improvement in the ability to easily discriminate subendocardial MI by providing a T2-weighted image with high contrast between blood and MI. MCODE should improve both the detection and accurate sizing of MI. J. Magn. Reson. Imaging 2005. Published by Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose To evaluate the consistency and inversion time (TI) independence of phase-sensitive reconstruction (PSIR) delayed-enhancement (DE) MRI in a clinical setting. Materials and Methods Mid-ventricular short-axis DE images were acquired in 25 patients using three TIs: 1) optimized to null viable myocardium, 2) 50 msec less than optimal TI, and 3) 50 msec greater than optimal TI. At each TI, images were acquired with PSIR and without magIR. In each image, percent scar was computed as the ratio of nonviable to total pixels in the left ventricle (LV). Results In the magIR images, percent scar was 23% ± 15% (optimal), 11% ± 11% (short), and 22% ± 15% (long). In PSIR images, percent scar was 25% ± 15% (optimal), 22% ± 15% (short), and 22% ± 14% (long). Percent scar was significantly underestimated in magIR images with short TI, but no statistically significant difference in percent scar was observed at the optimal or long TIs. Conclusion DE-MRI is a robust imaging technique for clinical use. PSIR provided consistent image quality independently of TI, at least over the range of TIs evaluated in this study. However, neither image quality nor scar appearance in the PSIR images was significantly different from that in the magIR images when TI was at or above the null point of viable myocardium. J. Magn. Reson. Imaging 2005;21:650-655. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Following administration of Gd-DTPA, infarcted myocardium exhibits delayed enhancement and can be imaged using an inversion-recovery sequence. A conventional segmented acquisition requires a number of breath-holds to image the heart. Single-shot phase-sensitive inversion-recovery (PSIR) true-FISP may be combined with parallel imaging using SENSE to achieve high spatial resolution. SNR may be improved by averaging multiple motion-corrected images acquired during free breathing. PSIR techniques have demonstrated a number of benefits including consistent contrast and appearance over a relatively wide range of inversion recovery times (TI), improved contrast-to-noise ratio, and consistent size of the enhanced region. Comparison between images acquired using segmented breath-held turbo-FLASH and averaged, motion-corrected, free-breathing true-FISP show excellent agreement of measured CNR and infarct size. In this study, motion correction was implemented using image registration postprocessing rather than navigator correction of individual frames. Navigator techniques may be incorporated as well. Magn Reson Med 53:194-200, 2005. Published 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]