Cardiac motion of coronary arteries: Variability in the rest period and implications for coronary MR angiography

PURPOSE: To measure the duration of the rest period in the cardiac cycle, a parameter vital to data acquisition in coronary magnetic resonance (MR) angiography. MATERIALS AND METHODS: Motion of coronary arteries was measured in 13 patients by using breath-hold, biplane, conventional angiography, with frontal and :: lateral projections of the left and right coronary arteries acquired at 30 frames per second. The time courses of the coordinates of bifurcations of proximal parts of the coronary arteries were measured, from which the rest period (motion < 1 mm in orthogonal axes), velocity, displacement range, motion correlation, and reproducibility from heartbeat to heartbeat were estimated. RESULTS: Both the motion pattern and the amplitude varied substantially from patient to patient. The rest period varied from 66 to 333 msec (mean, 161 msec) for the left coronary artery and from 66 to 200 msec (mean, 120 msec) for the right coronary artery. CONCLUSION: The rest period for coronary arteries in the cardiac cycle varies substantially from patient to patient, which may cause quality to be inconsistent in current coronary MR angiography. A cardiac motion image prior to coronary data acquisition (preimage) may be used to estimate the optimal duration and timing in the cardiac cycle for coronary MR angiography.