Flow profiles in the left anterior descending and the right coronary artery assessed by MR velocity quantification: Effects of through-plane and in-plane motion of the heart

Purpose: The purpose of this work was to compare the temporal profiles of volume flow in the left anterior descending artery (LAD) and the right coronary artery (RCA) and to assess the effect of through-plane and in-plane myocardial motion. Method: In eight healthy volunteers, MR phase-difference velocity quantification was applied with prospective ECG triggering, pixel size of 1.16 x 0.98 mm² (LAD) or 1.25 x 0.98 mm² (RCA), velocity sensitivity of 40 cm/s, and data acquisition time window of 64 ms for LAD (3 k(y) lines per heartbeat) and 24 ms for RCA. In-plane motion was measured from the magnitude images. Results: In the LAD, systolic peak and mean flow values were 0.94 ± 0.28 and 0.30 ± 0.22 ml/s, respectively. Diastolic peak and mean flows were 2.42 ± 0.56 and 1.38 ± 0.43 ml/s. The systolic to diastolic ratio was 0.37 ± 0.12 for peak flow and 0.22 ± 0.15 for mean flow. Mean flow through the cardiac cycle was 59.1 ± 15.0 ml/min. In the RCA, systolic peak and mean flow values were 1.96 ± 0.69 and 0.74 ± 0.31 ml/s, respectively. Diastolic peak and mean flows were 1.80 ± 0.53 and 0.83 ± 0.20 ml/s. The systolic to diastolic ratio was 0.97 ± 0.58 for peak flow and 0.85 ± 0.39 for mean flow. Mean flow through the cardiac cycle was 38.4 ± 10.8 ml/min. The in-plane velocity of the coronary artery cross-section was 6.4 ± 1.8 cm/s for the LAD and 14.9 ± 4.0 cm/s for the RCA (given by peak values in diastole). Conclusion: It is confirmed noninvasively with MR that the LAD shows a predominantly diastolic flow, whereas the RCA shows about equal flow values in systole and diastole. Through-plane motion correction is required for assessing the true flow patterns. The in-plane velocities of the coronary artery cross-sections imply a maximum data acquisition time window, estimated at 58 ms for the LAD and at 23 ms for the RCA.