All patients underwent 16-MSCT coronary angiography ( Sensation 16 ; Siemens , Germany ) with collimation 16 x 0.75 mm and rotation time 375 ms. The attenuation in Hounsfield units ( HU ) achieved after each CM was determined at regions of interest ( ROIs ) placed at the origin of coronary arteries and on the ascending aorta , descending aorta , and pulmonary artery .
