Abstract: Objective The reconstructive intervals providing best image quality for non-invasive coronary angiography with 64-slice computed tomography(CT) were evaluated.Methods Contrast enhanced,retrospectively electrocardiography(ECG)-gated 64-slice CTcoronary angiography was performed in 64 patients.Depending on the average heart rate during scanning,patients were grouped as <65 bpm(n=36),65～79 bpm(n=18) and ≥80 bpm(n=10).Two blinded and independent readers assessed the image quality of each coronary segment with a diameter ≥1.5 mm using the following scores: 5,no motion artifacts;4,minor artifacts;3,moderate artifacts;2,severe artifacts;and 1,not evaluative.Results Best image quality was obtained in all coronary segments at 60% or 65% for groupⅠandⅡ.In group Ⅲ.The left main artery,the left anterior descending artery and the left circumflex artery were clearly visualized at 60% of R-Rphases,while the right coronary artery was seen at 40% of R-Rphases.Conclusion When heart rate is <80bpm,64-slice CTcoronary angiography provides best image quality in mid-diastole,diagnostic image quality of all coronary segments can be obtained at reconstruction interval of 60% or 65%.When heart rate is ≥80 bpm,the right and left coronary artery should be reconstructed respectively to improve the image quality of coronary.

Key words: 64-slice CT, coronary angiography, reconstruction interval