Coronary artery motion during the cardiac cycle and optimal ECG triggeringfor coronary artery imaging

RATIONALE AND OBJECTIVES, Our purpose was to investigate the motion charact eristics of the coronary arteries and determine optimal electrocardiographi c (ECG) trigger time during the cardiac cycle to minimize motion artifacts, METHODS, Contrast-enhanced multislice movie studies of electron beam tomogr aphy (EBT) images were performed on 70 subjects, The EBT datasets, which co vered an entire cardiac cycle at 58-ms intervals, were acquired for a short -axis view of the heart with ECG triggering, The pixel values along x and y axes were measured at multiple intervals during the cardiac cycle to estab lish the motion distance and velocity of three major coronary arteries, RESULTS, Coronary artery motion varied greatly throughout the cardiac cycle in three major coronary arteries and increased with the patient's baseline heart rate, The greatest and lowest velocities of coronary arterial moveme nt during the cardiac cycle were determined, Based on the lowest velocity o f right coronary artery movement during the cardiac cycle, the optimal ECG trigger times were located at approximately 35% (31.4%-37.6%) or 70% (68.7% -71.4%) of the R-R interval in patients whose resting heart rate was less t han or equal to 70 beats per minute (bpm); at 50% (47.2%-61.1%) of the R-R interval in the 71- to 100-bpm group; and at 55% (52.8%-59.1%) of the R-R i nterval in the >100-bpm group, Our data demonstrated that the motion charac teristics of the left circumflex artery were quite similar to those of the right coronary artery and that the left anterior descending coronary artery had no significant differences in motion throughout the cardiac cycle. A m inimum scan speed of 35.4 to 75.5 ms per slice is needed to completely dimi nish cardiac motion artifacts (in-plane coronary artery motion with <1-mm d isplacement), CONCLUSIONS. For coronary artery screening, the optimal ECG trigger time sh ould be determined according to the patient's heart rate, thus greatly redu cing motion and motion artifacts during 100-ms acquisitions.