Background: Effective suppression of cardiac motion is crucial for MR coronary angiography (MRCA). Thus, we evaluated a new technique for rapid and automatic detection of the cardiac rest period in comparison to the conventional visual assessment of the coronary artery rest periods.
Methods: One hundred and thirty-five consecutive cardiac patients were examined (Philips Intera CV 1.5 T, Best, The Netherlands). Visual assessment of the left and right coronary rest periods was done using a cine-SSFP scan with a transversal slice orientation (retrospective gating, 40 phases/cardiac cycle); the coronary rest period was defined as the duration of the coronary artery being completely within a region of interest placed on the outer edge of the cross-section of the vessel. Common coronary rest period as determined from visual assessment was defined as the intersection of both coronary artery rest periods. For comparison, an automatic technique was applied: using the position of the shim volume to define a correlation kernel, the cross-correlations of consecutive cine images were registered and displayed in a graph. Based on these cross-correlation values, the cardiac rest period was detected. The correlation between the visual and automated analysis was assessed.
Results: A high correlation between the automatically and visually determined starting points for the coronary artery rest periods and the cardiac rest period was found. The automatically assessed cardiac rest period was significantly shorter in comparison to the visually assessed left and right coronary artery rest period (103 +/- 46 ms vs. 158 +/- 72 ms and 117 +/- 52 ms, respectively; p < 0.001). However, the common coronary rest period demonstrated excellent agreement with the cardiac rest period (r = 0.93, p < 0.001) without a significant difference in duration (109 +/- 52 ms vs. 103 +/- 46 ms).
Conclusions: Automated analysis of the cardiac rest period yielded similar results compared to the visual analysis. This rapid assessment of a cardiac acquisition window may be most helpful for MRCA, especially when aiming at 3-dimensional coverage of the whole coronary arterial tree during a single scan.