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 v olume flow in the left anterior descending artery (LAD) and the right coron ary artery (RCA) and to assess the effect of through-plane and in-plane myo cardial motion. Method: In eight healthy volunteers, MR phase-difference velocity quantific ation was applied with prospective ECG triggering, pixel size of 1.16 x 0.9 8 mm(2) (LAD) or 1.25 x 0.98 mm(2) (RCA), velocity sensitivity of 40 cm/s, and data acquisition time window of 64 ms for LAD (3 k, 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 0.3 7 +/- 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. D iastolic 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 val ues in diasrole). Conclusion: It is confirmed noninvasively with MR that the LAD shows a pred ominantly diastolic flow, whereas the RCA shows about equal flow values in systole and diastole. Through-plane motion correction is required for asses sing 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.