Computed tomography coronary angiography with 370-millisecond gantry rotation time: evaluation of the best image reconstruction interval

OBJECTIVE: To evaluate the best reconstruction window for noninvasive coronary angiography when using a 16-detector row computed tomography (CT) scanner with a gantry rotation time of 370 milliseconds. METHODS: In a pilot study, 189 coronary artery segments of 21 patients with a mean heart rate of 65 beats per minute (bpm, maximum: 45-94 bpm) were investigated using a 16-detector row CT scanner. Raw data were reconstructed in 10% increments from 40% to 70% of the RR interval. Two experienced observers independently evaluated the image quality of the coronary arteries in a segmental fashion. A 5-point ranking scale was applied, with 1 being very poor (no evaluation possible); 2, poor; 3, moderate; 4, good; and 5, very good. RESULTS: In the mean of all patients, the best reconstruction window was found to be at 60% of the RR interval. In patients with higher heart rates, the best reconstruction window was found to be at an earlier stage of the R wave-to-R wave interval. CONCLUSIONS: Initial results show that good diagnostic image quality could be achieved for all evaluated segments of the coronary tree with image reconstructions at 60% of the R wave-to-R wave interval in patients with heart rates of 70 bpm or less. Using a 16-detector row CT scanner with a gantry rotation time of 370 milliseconds, the need for adapting the reconstruction window to each segment for the best image quality was overcome in those cases. In patients with heart rates faster than 70 bpm, reconstructions at an earlier stage within the cardiac cycle were necessary.