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Like X-Ray contrast angiography, MR coronary angiograms show the vessel lumens rather than the vessels themselves. Consequently, outward remodeling of the vessel wall, which occurs in subclinical coronary disease before luminal narrowing, cannot be seen. The current gold standard for assessing the coronary vessel wall is intravascular ultrasound, and more recently, optical coherence tomography, both of which are invasive and use ionizing radiation. A noninvasive, low-risk technique for assessing the vessel wall would be beneficial to cardiologists interested in the early detection of preclinical disease and for the safe monitoring of the progression or regression of disease in longitudinal studies. In this review article, the current state of the art in MR coronary vessel wall imaging is discussed, together with validation studies and recent developments.

Regional myocardial function can be measured by several MR techniques including tissue tagging, phase velocity mapping, and more recently, displacement encoding with stimulated echoes (DENSE) and strain encoding (SENC). Each of these techniques was developed separately and has undergone significant change since its original implementation. As a result, in the current literature, the common features and the differences between the techniques and what they measure are often unclear and confusing. This review article delivers an extensively referenced introductory text which clarifies the current methodology from the starting point of the Bloch equations. By doing this in a consistent way for each method, the similarities and differences between them are highlighted. In addition, their capabilities and limitations are discussed, together with their relative advantages and disadvantages. While the focus is on sequence design and development, the principal parameters measured by each technique are also summarized, together with brief results, with the reader being directed to the extensive literature on data processing and clinical applications for more detail.

Purpose: To demonstrate coronary artery wall thickening with age in a small healthy cohort using a highly efficient, reliable, and reproducible high-resolution MR technique. Materials and Methods: A 3D cross-sectional MR vessel wall images (0.7 × 0.7 × 3 mm resolution) with retrospective beat-to-beat respiratory motion correction (B2B-RMC) were obtained in the proximal right coronary artery of 21 healthy subjects (age, 22–62 years) with no known cardiovascular disease. Lumen and outer wall (lumen + vessel wall) areas were measured in one central slice from each subject and average wall thickness and wall area/outer wall area ratio (W/OW) calculated. Results: Imaging was successful in 18 (86%) subjects with average respiratory efficiency 99.3 ± 1.7%. Coronary vessel wall thickness and W/OW significantly correlate with subject age, increasing by 0.088 mm and 0.031 per decade respectively (R = 0.53, P = 0.024 and R = 0.48, P = 0.046). No relationship was found between lumen area and vessel wall thickness (P = NS), but outer wall area increased significantly with vessel wall thickness at 19 mm2 per mm (P = 0.046). This is consistent with outward vessel wall remodeling. Conclusion: Despite the small size of our healthy cohort, using high-resolution MR imaging and B2B-RMC, we have demonstrated increasing coronary vessel wall thickness and W/OW with age. The results obtained are consistent with outward vessel wall remodeling. J. Magn. Reson. Imaging 2011;. © 2011 Wiley-Liss, Inc.

Purpose To demonstrate the feasibility of retrospective beat-to-beat correction of respiratory motion, without the need for a respiratory motion model. Materials and Methods A high-resolution three-dimensional (3D) spiral black-blood scan of the right coronary artery (RCA) of six healthy volunteers was acquired over 160 cardiac cycles without respiratory gating. One spiral interleaf was acquired per cardiac cycle, prior to each of which a complete low-resolution fat-selective 3D spiral dataset was acquired. The respiratory motion (3D translation) on each cardiac cycle was determined by cross-correlating a region of interest (ROI) in the fat around the artery in the low-resolution datasets with that on a reference end-expiratory dataset. The measured translations were used to correct the raw data of the high-resolution spiral interleaves. Results Beat-to-beat correction provided consistently good results, with the image quality being better than that obtained with a fixed superior–inferior tracking factor of 0.6 and better than (N = 5) or equal to (N = 1) that achieved using a subject-specific retrospective 3D translation motion model. Conclusion Non-model-based correction of respiratory motion using 3D spiral fat-selective imaging is feasible, and in this small group of volunteers produced better-quality images than a subject-specific retrospective 3D translation motion model. J. Magn. Reson. Imaging 2007;26:624–629. © 2007 Wiley-Liss, Inc.

Purpose To improve dark-blood and short tau inversion recovery (STIR) prepared turbo spin-echo (TSE) imaging of the heart, particularly in the basal short-axis plane where cardiac misregistration between the preparation and imaging phases is high. Materials and Methods In the first approach (tracked), the basal short-axis plane was labeled and tracked over the cardiac cycle. The slice-selective 180° dark-blood and STIR preparation pulses were then independently positioned on the appropriately timed labeled images. In the second approach (offset), the preparation pulses were output in the same orientation as the imaging plane, but with a user-defined slice offset that was derived from the labeled data. Both approaches were compared with the standard untracked dark-blood STIR TSE sequence (7-mm slice thickness) in 10 healthy volunteers. Results For typical preparation slice thicknesses, tracked and offset TSE images were superior to the untracked images (both P < 0.01). For the more mobile right ventricle (RV), the image quality of the tracked images was superior to that of the offset images (P < 0.05). Conclusion Tracking the through-plane motion of the heart between preparation and imaging phases improves the quality of thin-slice basal short-axis TSE images, particularly for the more mobile RV. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc.

Purpose To compare a volume-selective three-dimensional turbo spin echo (TSE) technique with ultrasound (US) for assessing carotid artery wall structure and function. Materials and Methods A three-dimensional volume-selective TSE technique was used to image the carotid artery in 10 healthy subjects and five hypertensive subjects (each of whom were scanned three times while they received different hypertension treatments). Lumen and wall area were measured on MR images. Two-dimensional US measurements of the intima-media thickness (IMT) and lumen diameter were taken in three orientations through a single cross section. The lumen area change over the cardiac cycle was used to determine distension. For validation, a Bland-Altman analysis was used to compare the vessel wall and lumen areas measured by three-dimensional MRI volumes with those obtained by US scans. Results Agreement between the two methods was found. The mean difference in distension between US and MRI was 1.2% (±5.1%). For the wall area measurements, good agreement was shown, but there was a systematic difference due to the visualization of the adventitia by MRI. Both techniques offer an easy way to objectively measure lumen indices. MRI can provide the complete circumference over the length of a vessel, while US is flexible and relatively inexpensive. The application of US is limited, however, when subjects are poorly echogenic. A difference between hypertensive and healthy subjects was found. Conclusion There was a good agreement between MRI and the clinically established two-dimensional US method. The MRI method has the advantage of providing increased vessel coverage, which permits one to assess localized abnormalities without assuming vessel uniformity. J. Magn. Reson. Imaging 2005;21:282–289. © 2005 Wiley-Liss, Inc.

Purpose To develop a method of correcting both right and left coronary artery flow velocities for the through-plane motion of the vessel, in order to allow details in the temporal flow profiles to be viewed. Materials and Methods The methods developed use selective excitation and velocity mapping of the epicardial fat surrounding the artery, either in a separate acquisition (temporal resolution = 22 msec) or interleaved with the water-excitation acquisition (temporal resolution = 44 msec) used to determine coronary blood flow velocities. The two methods were compared in 10 right and 13 left coronary arteries in healthy volunteers. Results For the right coronary arteries, correction for through-plane motion significantly reduces the mean systolic flow velocity (75.3 mm/second vs. 90.0 mm/second, P < 0.01), while the mean diastolic flow velocity is unchanged (96.8 mm/second vs. 94.5 mm/second, P = ns). The resulting profiles are biphasic, with approximately equal flow in systole and diastole. For the left arteries, correction for through-plane motion reduces the mean systolic flow velocity (25.0 mm/second vs. 72.8 mm/second, P < 0.001), resulting in the expected diastolic predominant flow profiles. For the right arteries, there were no significant differences in the mean systolic and mean diastolic velocities after correction with the separate fat-excitation acquisition, and after correction the poorer temporal resolution combined water excitation/fat excitation acquisition. However, for the left coronary arteries, the combined water excitation/fat excitation acquisition resulted in a slight reduction in the mean diastolic velocity (121.5 mm/second vs. 130.9 mm/second, P < 0.05). Conclusion Selective excitation of the surrounding epicardial fat enables through-plane correction of both left and right coronary flow velocities, enabling the temporal details of flow velocity to be viewed.With a combined WE/FE acquisition, this can be performed without extending the study duration; however, the reduced temporal resolution and temporal mismatch of the excitations results in a blunting of rapidly changing flow profiles. As such, it may be less suitable for the left coronary artery, which has a greater range of through-plane motion than the right, and correction using separate WE and FE acquisitions, or the adjacent myocardium, may be preferable. J. Magn. Reson. Imaging 2004;20:953–960. © 2004 Wiley-Liss, Inc.

Purpose To develop a breath-hold segmented sequence which generates similar patterns of signal loss to a non–breath-hold, relatively long echo time, conventional gradient echo sequence for the qualitative assessment of valvular heart disease. Materials and Methods Both velocity-sensitized and acceleration-sensitized segmented sequences were developed. The sensitivities were empirically adjusted to give similar degrees of signal loss to a conventional sequence. These sequences were compared with a conventional sequence in eight patients with flow disturbances and in four healthy subjects. Results There was no significant difference in the extent of signal loss observed when using the breath-hold velocity- and acceleration-sensitized sequences developed and the conventional sequence (1862 mm2, 1831 mm2, and 1782 mm2, respectively; P = ns). However, the image quality obtained was significantly better with the breath-hold sequences (both P < 0.01). Furthermore, the image quality achieved with the acceleration-sensitized sequence was significantly better than that achieved with the velocity-sensitized sequence (P < 0.01) where artifacts from beat-to-beat variations in blood-flow velocities were a frequent problem. Conclusion Signal loss in complex flow is best demonstrated using the breath-hold acceleration-sensitized sequence where the signal from both stationary and constant velocity material is rephased at the echo time.

Purpose To use a volume-selective 3D turbo spin echo (TSE) technique to image the carotid artery wall and measure distensibility. Materials and Methods A high-resolution volume-selective 3D TSE sequence has been developed. Volume selection is accomplished by orthogonal gradients for the 90° and 180° excitations and allows a 3D volume of vessel wall to be imaged in a relatively short time. The technique has been developed to allow imaging at any defined phase of the cardiac cycle so that the vascular function and distensibility can be studied. Results Scan efficiency is increased by the reduced phase encode field of view (FOV) (ky steps) by the use of selective volume excitation. Significantly more slices (kz phase encode steps) for vessel coverage can be acquired with the same scan time as that of the conventional sequence while maintaining signal-to-noise ratio (SNR) levels. The practical value of the technique was demonstrated on 10 normal subjects with high-resolution vessel distensibility measurements of the carotid arteries. Conclusion A volume-selective TSE method has been used for carotid artery wall imaging and measurement of distensibility in normal subjects. Larger coverage of the vessel, and therefore more information for clinical diagnostics, was achieved with the same overall scan time with an SNR comparable to that of 2D full FOV images. J. Magn. Reson. Imaging 2003;17:572–580. © 2003 Wiley-Liss, Inc.

To examine magnetic resonance coronary artery imaging after NC100150-Injection.Breath-hold and navigator-gated images were acquired in five patients.Breath-hold image quality, coronary artery-fat SDNR, and coronary artery SNR improved. Respiratory artifacts due to reduced liver signal intensity degraded navigator-gated image quality.NC100150-Injection improves breath-hold coronary artery imaging. Navigator-gated acquisitions should use techniques that are insensitive to T2* effects.

We evaluated free-breathing, prospective navigator-gated, three-dimensional (3D) magnetic resonance coronary angiography (MRCA) with hybrid ordered phase-encoding (HOPE), in the detection of proximal coronary artery stenosis. The coronary arteries were imaged in 46 patients undergoing cardiac catheterization. The mean scan time was 48 minutes. The mean arterial length (mm) visualized was left main stem (LMS) 11.7 (SD 4.5), left anterior descending (LAD) 30.1 (SD 11.1), circumflex (LCx) 15.5 (SD 8.6), and right (RCA) 56.2 (SD 20.8). Twenty-three patients had coronary artery disease with 47 significant stenoses on cardiac catheterization. All LMS were normal on both catheterization and MRCA. MRCA sensitivity was highest for the LAD (89% CI 65%-99%) and RCA (76% CI 50%-93%), but lower for the LCx (50% CI 21%-79%). Specificity ranged from 72%-100%. Improvements in image quality, length of vessel seen, and specific imaging of the LCx are required for MRCA to become an alternative to cardiac catheterization.

Temporal changes in respiration could influence navigator-echo (NE)-gated MR coronary angiography (MRCA), but systematic investigation of the effects of such variations and how to limit them has not been performed. We addressed these issues by studying the influence of time in the magnet on diaphragm position and respiratory patterns using NE diaphragm monitoring in volunteers and a phantom model. NE diaphragm monitoring was performed at .5 T in 10 subjects over a total period of 35 minutes. The end-expiratory position was sustained for longer (1.1 vs .4 seconds, P < .001) and with greater position stability (SD 1.9 vs 5.9 mm, P = .01) than the end-inspiratory position. Drift of the end-expiratory position occurred over time, causing a fall in scan efficiency (44-28%, P = .01). Up-drift of the end-expiratory position was most common. Loss of scan efficiency was worse with up-drift because of loss of the end-expiratory pause from the NE window (up-drift 10% mm-1, down-drift 7% mm-1, both P = .03). Scan efficiency also was reduced during sleep (to a nadir of 0%), secondary to loss of the end-expiratory pause, periodic breathing with oscillating end-expiratory position, and periods of apnea. The phantom model used actual diaphragm traces to evaluate the artifact resulting from diaphragm motion during acquisition. Artifact was considerably reduced by NE adaptive motion correction compared with NE gating alone (ghosting ratio 2.0 vs 2.8, P < .01). Artifact also was significantly reduced with up-drift if scan efficiency was maintained above 35% (P = .05). For optimal NE-gated MRCA, the following features are important: the NE window should be placed around the end-expiratory position; subjects should not sleep; scan efficiency should be monitored and the NE window should be repositioned if scan efficiency falls below 35%; and adaptive motion correction should be used.