Abstract： Objective To evaluate the multi-phase imaging ability of dual source CT coronary angiography and the effects of whole-phase interval reconstruction and the four dimensional(4D)mode of"Inspace"software on the imaging quality of dual source CT coronary angiography.Methods Fifty patients performed coronary CT angiography(CTA),and the images were reconstructed from 10% to 100% of the R-R interval(the reconstruction interval was 10%).The imaging quality scores of the three main coronary arteries were assessed by two experienced radiologists using the 4D mode of"Inspace"software On workstation.Results The average scores of imaging quality in the RCA.LAD and LCX at all 10 reconstruction phases were 1.71,2.57 and 2.03 respectively. The scores of imaging quality in the three main coronary arteries were all over 2.0 when the reconstruction phase were at 30%,40%and 70%of the cardiac circle.The imaging quality scores in the three main coronary arteries reached 3 at least one phase both in systole(10%-40%)and in diastole(50%-100%)in 41 cases(82%).The imaging quality scores in the left anterior descending artery reached 2 at all phases in 25 cases(50%),and reached 3 in 5 cases(10%).Conclusion Dual source CT coronary angiography can achieve good image quality in mid-late systole(30%-40%)or mid-diastole(70%).