Repositioning precision of coronary arteries measured on X-ray angiography and its implications for coronary MR angiography

Background To test the hypothesis that intervals with superior beat-to-beat coronary artery repositioning precision exist in the cardiac cycle, to design a coronary MR angiography (MRA) methodology in response, and to ascertain its performance. Methods Coronary repositioning precision in consecutive heartbeats was measured on x-ray coronary angiograms of 17 patients and periods with the highest repositioning precision were identified. In response, the temporal order of coronary MRA pulse sequence elements required modification and the T₂-prep now follows (T₂-post) rather than precedes the imaging part of the sequence. The performance of T₂-post was quantitatively compared (signal-to-noise [SNR], contrast-to-noise [CNR], vessel sharpness) to that of T₂-prep in vivo. Results Coronary repositioning precision is <1 mm at peak systole and in mid diastole. When comparing systolic T₂-post to diastolic T₂-prep, CNR and vessel sharpness remained unchanged (both P=NS) but SNR for muscle and blood increased by 104% and 36% (both P<0.05), respectively. Conclusion Windows with improved coronary repositioning precision exist in the cardiac cycle: one in peak systole and one in mid diastole. Peak-systolic imaging necessitates a re-design of conventional coronary MRA pulse sequences and leads to image quality very similar to that of conventional mid-diastolic data acquisition but improved SNR. J. Magn. Reson. Imaging 2015;41:1251-1258.