Coronary arteries: Retrospectively ECG-gated multi-detector row CT angiography with selective optimization of the image reconstruction window

PURPOSE: To investigate how the technique of retrospective gating can be used to optimize reconstruction of multi-detector row computed tomographic (CT) images for each of the three major coronary arteries during the cardiac cycle. MATERIALS AND METHODS: Multi-detector row coronary CT angiograms obtained in 50 patients were reconstructed at 20%-80% of the cardiac cycle in increments of 10%. Two blinded independent reviewers assessed the image quality, in terms of artifacts and visibility, obtained with three-dimensional postprocessing for segments 1-3 (right coronary artery), segments 5-8 (left main and left anterior descending coronary arteries), and segments 11 and 12 (left circumflex artery). The following grades were assigned: 1, very poor; 2, poor; 3, fair; 4, good; and 5, excellent. RESULTS: The left anterior descending artery was best visualized in middiastole at 60%-70% of the cardiac cycle, and the left circumflex artery was best visualized at 50%. The optimal reconstruction window for the right coronary artery was significantly different at 40% (P < .05). Although there was good agreement (κ 0.75) between the two reviewers, there was a high degree of variation in the patient population. CONCLUSION: The image reconstruction window for CT angiography of the coronary arteries should be adapted to each coronary artery. The use of one fixed time point in the cardiac cycle for image reconstruction does not provide optimal image quality.