ECG-gated reconstructed multi-detector row CT coronary angiography: Effectof varying trigger delay on image quality

PURPOSE: To evaluate the effectiveness of electrocardiographically (ECG)-ga ted retrospective image reconstruction for multi-detector row computed tomo graphic (CT) coronary angiography in reducing cardiac motion artifacts and to evaluate the influence of heart rate on cardiac image quality. MATERIALS AND METHODS: Sixty-five patients with different heart rates under went coronary CT angiography. Raw helical CT data and ECG tracings were com bined to retrospectively reconstruct at the defined consecutive z position with a temporal resolution of 250 msec per section. The starting points of the reconstruction were chosen between 30% and 80% of the R-R intervals. Th e relationships between heart rate, trigger delay, and image quality were a nalyzed. RESULTS: Optimal image quality was achieved with a 50% trigger delay for th e right coronary artery and 60% for the left circumflex coronary artery. Op timal image quality for the left anterior descending coronary artery was eq ually obtained at 50% and 60% triggering. A significant negative correlatio n was observed between heart rate and image quality (P < .05). The best ima ge quality was achieved when the heart rate was less than 74.5 beats per mi nute. CONCLUSION: To achieve high image quality, the heart rate should be suffici ently slow. Selection of appropriate trigger delays and a decreasing heart rate are effective to reduce cardiac motion artifacts.