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To pathologically verify the correlation between native TThirty New Zealand white rabbits were randomly divided into the control group (n = 6), diabetes 3 months group (n = 8), diabetes 6 months group (n = 8), and diabetes 9 months group (n = 8). All the rabbits underwent clinical 3.0T magnetic resonance (MR) examinations with pre- and postcontrast modified Look-Locker inversion recovery TTwo rabbits died in each diabetes group, thus each group included six rabbits. ECV calculated from pre- and postcontrast TECV has a very strong correlation with pathological CVF, and can be used to assess the degree of diffuse myocardial fibrosis better than the postcontrast T

Purpose: To investigate whether a statistical analysis of myocardial blood-oxygen-level-dependent (mBOLD) signal intensities can lead to the identification and quantification of the ischemic area supplied by the culprit artery. Materials and Methods: Cardiac BOLD images were acquired in a canine model (n = 9) with controllable LCX stenosis at rest and during adenosine infusion on a 1.5T clinical scanner. Statistical distributions of myocardial pixel-intensities derived from BOLD images were used to compute an area metric (ischemic extent, IE). True myocardial perfusion was estimated from microsphere analysis. IE was compared against a standard metric (segment-intensity-response, SIR). Additional animals (n = 3) were used to investigate the feasibility of the approach for identifying ischemic territories due to LAD stenosis from mBOLD images. Results: Regression analyses showed that IE and myocardial flow ratio between rest and adenosine infusion (MFR) were exponentially related (R2 > 0.70, P < 0.001, for end-systole and end-diastole), while SIR and MFR were linearly related to end-systole (R2 = 0.51, P < 0.04) and unrelated to end-diastole (R2 ≈ 0, P = 0.91). Receiver-operating-characteristic analysis that IE was superior to SIR for detecting critical stenosis (MFR ≤2) in end-systole and end-diastole. Feasibility studies on LAD narrowing demonstrated that the proposed approach could also identify oxygenation changes in the LAD territories. Conclusion: The proposed evaluation of cardiac BOLD magnetic resonance imaging (MRI) offers marked improvement in sensitivity and specificity for detecting critical coronary stenosis at 1.5T compared to the mean segmental intensity approach. Patient studies are now warranted to determine its clinical utility. J. Magn. Reson. Imaging 2012;35:1338–1348. © 2012 Wiley Periodicals Inc.

Purpose: To assess the hypothesis that steady-state free procession (SSFP) allows for imaging of the coronary wall under the conditions of fast heart rate in heart transplantation (HTx) patients. Materials and Methods: With the approval of our Institutional Review Board, 28 HTx patients were scanned with a 1.5T scanner. Cross-sectional black-blood images of the proximal portions of the left main artery, left anterior descending artery, and right coronary artery were acquired with both a 2D, double inversion recovery (DIR) prepared turbo (fast) spin echo (TSE) sequence and a 2D DIR SSFP sequence. Image quality (scored 0–3), vessel wall area, thickness, signal-to-noise ratio (SNR, vessel wall), and contrast-to-noise ratio (CNR, wall-lumen) were compared between TSE and SSFP. Results: The overall image quality of SSFP was higher than TSE (1.23 ± 0.95 vs. 0.88 ± 0.69, P < 0.001). SSFP had a higher coronary wall SNR (20.1 ± 8.5 vs. 14.9 ± 4.8, P < 0.001) and wall-lumen CNR (8.2 ± 4.6 vs. 6.8 ± 3.7, P = 0.005) than TSE. Conclusion: Black-blood SSFP coronary wall MRI provides higher image quality, SNR, and CNR than traditional TSE does in HTx recipients. It has the potential to become an alternative means to noninvasive imaging of cardiac allografts. J. Magn. Reson. Imaging 2012;35:1210-1215. © 2012 Wiley Periodicals, Inc.

Purpose: To develop a 3D flow-independent peripheral vessel wall imaging method using T2-prepared phase-sensitive inversion-recovery (T2PSIR) steady-state free precession (SSFP). Materials and Methods: A 3D T2-prepared and nonselective inversion-recovery SSFP sequence was designed to achieve flow-independent blood suppression for vessel wall imaging based on T1 and T2 properties of the vessel wall and blood. To maximize image contrast and reduce its dependence on the inversion time (TI), phase-sensitive reconstruction was used to restore the true signal difference between vessel wall and blood. The feasibility of this technique for peripheral artery wall imaging was tested in 13 healthy subjects. Image signal-to-noise ratio (SNR), wall/lumen contrast-to-noise ratio (CNR), and scan efficiency were compared between this technique and conventional 2D double inversion recovery – turbo spin echo (DIR-TSE) in eight subjects. Results: 3D T2PSIR SSFP provided more efficient data acquisition (32 slices and 64 mm in 4 minutes, 7.5 seconds per slice) than 2D DIR-TSE (2–3 minutes per slice). SNR of the vessel wall and CNR between vessel wall and lumen were significantly increased as compared to those of DIR-TSE (P < 0.001). Vessel wall and lumen areas of the two techniques are strongly correlated (intraclass correlation coefficients: 0.975 and 0.937, respectively; P < 0.001 for both). The lumen area of T2PSIR SSFP is slightly larger than that of DIR-TSE (P = 0.008). The difference in vessel wall area between the two techniques is not statistically significant. Conclusion: T2PSIR SSFP is a promising technique for peripheral vessel wall imaging. It provides excellent blood signal suppression and vessel wall/lumen contrast. It can cover a 3D volume efficiently and is flow- and TI-independent. J. Magn. Reson. Imaging 2010;32:399–408. © 2010 Wiley-Liss, Inc.

Purpose—To investigate the accuracy of a dual-projection respiratory self-gating (DP-RSG) technique in dynamic heart position measurement and its feasibility for free-breathing whole-heart coronary MR angiography (MRA). Materials and Methods—A DP-RSG method is proposed to enable accurate direct measurement of heart position by acquiring two whole-heart projections. On 14 volunteers, we quantitatively evaluated the efficacy of DP-RSG by comparison with diaphragmatic navigator (NAV) and single-projection-based respiratory self-gating (SP-RSG) methods. For DP-RSG, we also compared center-of-mass and two profile-matching algorithms in deriving heart motion. Coronary imaging was conducted on 8 volunteers based on retrospective gating to preliminarily validate the effectiveness of DP-RSG for whole-heart coronary MRA. Comparison of vessel delineation was performed between images reconstructed using different gating methods. Results—The quantitative evaluation shows that DP-RSG more accurately tracks heart motion than NAV with all gating window (GW) values and SP-RSG approaches with GW ≥2.5mm and profile-matching algorithms are more reliable for motion derivation than center-of-mass calculations with GW ≥1.0mm. Whole-heart coronary MRA studies demonstrate the feasibility of using DP-RSG to improve overall delineation of the coronary arteries. Conclusion—DP-RSG is a promising approach to better resolve respiratory motion for wholeheart coronary MRA compared to conventional NAV and SP-RSG.

Purpose To examine the dependence of steady-state free-precession (SSFP) -based myocardial blood-oxygen-level-dependent (BOLD) contrast on field strength using theoretical and experimental models. Materials and Methods Numerical simulations using a two-pool exchange model and a surgically prepared dog model were used to assess the SSFP-based myocardial BOLD signal changes at 1.5T and 3.0T. Experimental studies were performed in eight canines with pharmacological vasodilation under various levels of left circumflex coronary artery stenosis. Experimentally obtained BOLD signal changes were correlated against microsphere-based true flow changes. Results Theoretical results showed that, at 3.0T, relative to 1.5T, a threefold increase in oxygen sensitivity can be expected. Experimental studies in canines showed near similar results—a 2.5 ± 0.2-fold increase in BOLD sensitivity at 3.0T relative to 1.5T (P < 0.05). Based on the scatter gram of BOLD data and microsphere data, it was found that the minimum regional flow difference that can be detected with SSFP-based myocardial BOLD imaging at 1.5T and 3.0T were 2.9 and 1.6, respectively (P < 0.05). Conclusion This study demonstrated that SSFP-based myocardial BOLD sensitivity is substantially greater at 3.0T compared with 1.5T. The findings here suggest that SSFP-based myocardial BOLD imaging at 3.0T may have the necessary sensitivity to detect the clinically required minimum flow difference of 2.0. J. Magn. Reson. Imaging 2008;27:1037–1045. © 2008 Wiley-Liss, Inc.

Purpose To assess a swallowing-compensated, three-dimensional (3D) diffusion-prepared segmented steady-state free precession (3D Nav-D-SSFP) technique for carotid wall MRI with 0.6-mm isotropic spatial resolution, and its utility for semiautomated carotid wall morphometry. Materials and Methods The carotid arteries of seven healthy volunteers (N = 14) were imaged with 3D Nav-D-SSFP and black-blood T2-weighted (T2w) two-dimensional (2D) fast spin-echo (FSE). Carotid wall-lumen contrast-to-noise ratio (CNR) was measured with both sequences. Measurement of carotid wall area (WA) and lumen area (LA) made in a semiautomated manner off of the 3D Nav-D-SSFP images were compared to those made manually. Results Adjusted for voxel volume and number of slices, a near six-fold improvement in CNR per unit time was achieved with 3D Nav-D-SSFP relative to 2D T2w FSE (P < 0.001). Manual and semiautomated measurements of carotid WA and LA on the 3D Nav-D-SSFP images were highly correlated (intraclass correlation coefficient (ICC) = 0.961 and 0.996, respectively; P < 0.001). Conclusion 3D Nav-D-SSFP is a time-efficient, swallowing-compensated, black-blood technique that lends itself for semiautomated measurements of carotid WA and LA that are in good agreement with manual measurements. J. Magn. Reson. Imaging 2007. © 2007 Wiley-Liss, Inc.

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.

MAGNETIC RESONANCE IMAGING (MRI) HAS been proposed as a potential alternative to x-ray fluoroscopy for performing coronary artery interventions (1). MRI-guided procedures have several advantages over x-ray fluoroscopy: the patient and medical staff are not exposed to ionizing radiation, nephrotoxic contrast agent is not used, it is possible to obtain functional as well as anatomical information, and MRI is able to obtain two-and three-dimensional data sets in any arbitrary image orientation. However, MRI-guided interventions are still limited by the achievable spatial resolution, temporal resolution, and vessel signal of the MR image. Selective catheter-directed coronary angiography is an essential component of x-ray fluoroscopy-guided coronary procedures. MR angiography (MRA) of the coronary arteries with catheter-directed gadolinium (Gd)-based contrast injections have been shown to be feasible in animals (2). Previous studies have used a two-dimensional thick-slice projection technique with a gradient-recalled echo (GRE) sequence (2,3) or steady-state free precession (SSFP) (4) for data acquisition because imaging time is limited following intracoronary injection of contrast media. Rapid perfusion of contrast agent into the myocardium may obscure the coronary arteries during a prolonged imaging time. However, coronary artery delineation can be poor in two-dimensional projection imaging when the slice thickness is large, even when magnetization preparation or image subtraction is used to reduce background tissue signal because background tissue occupies a much larger volume of a given voxel than the artery of interest. An alternative approach is to use three-dimensional imaging for catheter-directed coronary MRA, which reduces voxel size and the partial-volume effect. However, three-dimensional imaging requires a much longer imaging time. Contrast agent begins enhancing myocardial signal in as little as 4 seconds following intracoronary injection (4), which can dramatically reduce coronary artery myocardium contrast-to-noise ratio (CNR) if the scan time is too long. This in turn limits the data acquisition window available for coronary artery MRA. A compromise would be to use three-dimensional imaging with a small number of thick partitions to minimize imaging time while maintaining the CNR advantage over two-dimensional imaging. In this study, we used two partitions for three-dimensional magnetization-prepared SSFP coronary artery MRA after intra-arterial (IA) contrast injection. We tested the hypothesis that this sequence improves coronary artery CNR in swine compared to two-dimensional projection imaging sequence with the same coverage and in-plane spatial resolution.

Purpose To assess the feasibility of three-dimensional breathhold coronary magnetic resonance angiography (MRA) at 3.0T using the steady-state free precession (SSFP) sequence, and quantify the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) gains of coronary MRA from 1.5T to 3.0T using whole-body and phased-array cardiac coils as the signal receiver. Materials and Methods Eight healthy volunteers were scanned on 1.5T and 3.0T whole-body systems using the SSFP sequence. Numerical simulations were performed for the SSFP sequence to optimize the flip angle and predict signal enhancement from 1.5T to 3.0T. Coronary artery images were acquired with the whole-body coil in transmit-receive mode or transmit-only with phased-array cardiac coil receivers. Results In vivo studies of the same volunteer group at both field strengths showed increases of 87% in SNR and 83% in CNR from 1.5T to 3.0T using a whole-body coil as the signal receiver. The corresponding increases using phased-array receivers were 53% in SNR and 92% in CNR. However, image quality at 3.0T was more variable than 1.5T, with increased susceptibility artifacts and local brightening as the result of increased B0 and B1 inhomogeneities. Conclusion Coronary MRA at 3.0T using a three-dimensional breathhold SSFP sequence is feasible. Improved SNR at 3.0T warrants the use of coronary MRA with faster acquisition and/or improved spatial resolution. Further investigations are required to improve the consistency of image quality and signal uniformity at 3.0T. J. Magn. Reson. Imaging 2005;22:206–212. © 2005 Wiley-Liss, Inc.

Purpose To minimize contrast agent dosage for intra-arterial (IA) contrast-enhanced magnetic resonance angiography (CE-MRA) by examining the effects of encoding order (elliptical vs. sequential) and injection duration (100% to 30% of the acquisition time). Materials and Methods Catheter-based IA gadolinium (Gd) injections were performed in an arterial flow phantom. Blood flow rates, injection rates, and injection durations were systematically varied. Signal-to-noise (SNR) measurements were obtained in the aorta, renal artery, and common iliac artery. Results No significant SNR losses were observed for any of the vessels with 75% injection duration, or for the aorta and iliac artery with 50% injection duration. Excellent images of all vessels were obtained at 50% injection duration. There was no significant SNR difference between encoding schemes. Conclusion Contrast agent dosage can be substantially reduced without loss of SNR by limiting injection to part of the imaging acquisition time. J. Magn. Reson. Imaging 2002;15:55–61. © 2002 Wiley-Liss, Inc.

Initial evaluation of a new blood pool agent, B-22956/1, for pulmonary imaging was performed in five domestic pigs with artificial embolism. Pre-embolism 3D pulmonary perfusion images were first acquired by injecting an extravascular agent, gadoteridol. The pulmonary arteries of the pigs were then occluded by the artificial emboli. Post-embolism perfusion scans were subsequently performed by injecting B-22956/1. Additional post-embolism high-spatial-resolution angiograms were also acquired. Parenchyma perfusion deficits were well depicted in the post-embolism perfusion maps. The post-embolism angiography clearly revealed the location and extent of the filling defects in the pulmonary vessels. Signal intensities of perfusion maps on the normal parenchyma were significantly improved (30%) by using B-22956/1, in comparison with perfusion images using gadoteridol (P < 0.01). Many pulmonary angiograms with approximately equal contrast could be obtained even at 22 minutes after the injection of B-22956/1. Our initial results indicate that blood pool agent B-22956/1 may provide opportunities for whole-lung-coverage perfusion mapping and additional high-resolution target angiograms after a single injection. J. Magn. Reson. Imaging 2001;14:425–432. © 2001 Wiley-Liss, Inc.

The purpose of the work was to evaluate the effectiveness of extracellular contrast media in improving MR coronary angiography using breath-hold segmented echo-planar imaging (SEPI). Two protocols were designed to optimize the inversion recovery-prepared contrast-enhanced SEPI method. In 15 healthy volunteers, significant improvements in signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, and length of visualization were observed post-contrast. The method with two targeted scans to cover the left and right arteries, respectively, following separate 20-mL contrast injections, was found to yield thinner slices and longer right coronary artery (RCA) visualization than a single scan following a 40-mL contrast injection without compromising SNR and CNR. In conclusion, extracellular contrast media substantially improves the delineation of coronary arteries with SEPI. J. Magn. Reson. Imaging 2001;13:676-681.

The in vivo relationship between blood T2* and oxygen saturation was investigated. A wide range of blood oxygen saturation levels was created in pigs by altering the ventilation rate. Blood T2* was measured in vivo in the abdominal aorta and the inferior vena cava, corresponding to each oxygen saturation level. Our results indicate that it is possible to measure blood T2* in vivo reliably with an MR technique we previously proposed. Blood T2* correlates closely with oxygen saturation levels over a wide range, and the relationship between blood T2* measured in vivo and oxygen saturation can be approximated by a linear function.

The accurate assessment of carotid artery disease is an important challenge for magnetic resonance (MR) angiography. Studies indicate that the detection and grading of stenosis and the evaluation of plaque morphology are all important steps in the clinical assessment of atherosclerosis. The prevalence of significant carotid artery stenosis in the elderly population and even in patients with symptoms of carotid artery disease is low; clinical risk seems to correlate more closely with plaque morphology and surface characterization than with the degree of stenosis. This highlights the importance of MR angiography and ultrasound, which can help characterize plaque morphology in addition to showing the degree of stenosis. The authors review the present understanding of plaque formation, comparisons of plaque imaging with conventional angiography, ultrasound, and MR angiography, and recent progress in MR angiography techniques. Several studies, including the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial, are discussed regarding the current objectives of carotid artery imaging. The sensitivity and specificity of plaque detection and morphologic evaluation continue to improve.