Objective To evaluate the arrival peak time (APT) of contrast medium to abdominal aorta at different dosages with 64-detector CT scanner.Methods Sixty cases with normal cardiac function were divided randomly into three groups(group A,B,C).The injection rate of group A,B,C was 4.5 ml/s,3.5 ml/s,4.5 ml/s respectively.A small test bolus and the enhancement dosage bolus were at the same injection rate.After the injection of contrast medium was done,20 ml saline chaser was followed in group A and B but group C.20 patients with cardiac dysfunction as group D received the same injection protocol as group A.The concentration of contrast medium was 370 mgI/ml and cine-modal was used in contrast-enhanced scanning.The time-density curve of abdominal aorta at the level of porta hepatic and APT were measured at the different group and the different dosage.Results APT of contrast medium of the small test bolus in group A,B,and C ranged from 19 s to 24 s with mean time(20?2) s,(19?3) s and(22?3) s respectively.In group D,APT ranged from 24 s to 42 s with mean time(28?14) s.APT of enhancement dosage ranged from 20 s to 26 s among group A, B,C with mean(22?3) s,(21?2) s and(24?2) s respectively.In group D,APT ranged from 26 s to 44 s,with mean time(32?14) s.The difference of APT between test bolus and enhancement dosage was 2~7 s among group A,B and C,and was 3~12 s in group D.Conclusion The APT of abdominal aorta at the level of porta hepatis between test bolus and enhancement dosage in the patients with normal cardiac function or with cardiac dysfunction is different.