Localization Strategy And Preliminary Clinical Application Of Coronary Magnetic Resonance Angiography

Part ITITLE: Localization Strategy and Imaging Quality Evaluation for Coronary Magnetic Resonance AngiographyPURPOSE: To investigate a simplified and practical localization strategy for coronary magnetic resonance angiography (CMRA), to evaluate the reliability of the breath-holding three-dimensional FIESTA sequence for direct visualization of main coronary vessels, and to reveal the causes and their controls for CMRA imaging quality.MATERIALS AND METHODS: 96 consecutive subjects accepted CMRA examinations on 1.5T GE MR scanner. The scanning protocol included interactive scouting of standard four-chamber view using real-time FIESTA sequence, cine FIESTA sequences on standard four-chamber view, short- and long- axis views of left ventricle and long-axis view of right ventricle for cardiac morphologic and kinetic evaluations. CMRA were acquired using ECG-gated, 3-dimensinal FIESTA sequence. All scans were completed during end-expiration breath-hold. LM, proximal and middle LAD, proximal and middle RCA as well as proximal LCX were localized on 9 steps in different plotting planes. ECG trigger-delay was accurately set to mid-diastolic "motion freezing" by observing the movement profile of RCA cross-points on four-chamber view individually. A Score-and-Grade image quality evaluation system was established. The respiratory motion, cardiac pulsation and tissue contrast were scored 0-2 and then the imaging quality was graded 0-IV according to the sum of the scores and compared with the conventional 0-IV scale image quality evaluation system. Length of visualized vessels was measured taking the standard coronary arterysegmentation system as reference and the reliability of each step to visualize the target vessels and the total reliability for the main branches visualization on the 9 steps were calculated.RESULTS: 86 subjects completed the examinations and 10 failed for poor breath-hold, hyper-arrhythmia, arrhythmia or probable coronary stenosis. The Score-and-Grade imaging quality evaluation system had a statistically significant correlation to the conventional 0-IV scale system where r=0.96 (t=84.5, P<0.05). It indicated the causes for the imaging quality degrading and was helpful for the improvement. Cardiac pulsation blurring, respiratory motion artifacts were weighted for the imaging degrading by 41.47%, 30.43% and 28.09, respectively. The accurate individual EGG trigger-delay setting could reduce the cardiac pulsation blurring to the minimum and improve the image quality. Totally, 94.82% acquisitions were graded over I and acceptable on the Score-and-Grade imaging evaluation system. When defined the direct visualization of continuous LM, proximal and middle RCA, proximal and middle LAD and proximal LCX as success, the reliabilities of each step to localize the target vessels ranged from 86.90% to 100% and the total reliability for LM, proximal and middle LAD, proximal LCX were 100% and 98.84% for proximal and middle RCA.CONCLUSIONS: The investigated localization strategy was based on the functional planes of the heart and could directly visualize the main coronary vessels including LM, proximal and middle LAD, proximal LCX, proximal and middle RCA. The multiple planar localizations could make complementary for direct visualization, which improve the reliability and compensate the poor inter-planar spatial resolution. The Sore-and-Grade evaluation system could accurately grade the imaging quality for CMRA and indicated the causes for imaging degrading, which is helpful for improvement.