Abstract: Objective: To discuss the influence of different injection rates of contrast medium with 64-slice helical CT on effect of liver arterial phase enhanced scanning.Methods: We retrospectively analyzed 80 patients for abdominal CT enhanced scanning.All patients were divided into two groups,the normal group(A group) and the cirrhosis group(B group),each group had 40 cases.According to the injection rate of contrast medium,each group was divided into 2 groups,the 3.5 mL/s group(group A1,B1) and 2.5 mL/s group(group A2,B2).Using Smartprep tracking technology of contrast medium,when the abdominal aorta CT value reached or exceeded 150 Hu,pressed the scan button and began formal scan.Under different injection rate of contrast medium,the peak enhancement of abdominal aorta and trigger time of arterial phase were measured.Recorded good and excellent rats of normal and cirrhotic group,then compared statistical results.Results: When the injection rate of contrast medium was 3.5 mL/s and 2.5 mL/s,The good and excellent rates of normal group was 96.4% and 91.7% respectively,P>0.05,and that of cirrhosis group was 95.5% and 72.2% respectively,P<0.05.When injection rate of contrast medium was 2.5 mL/s,the mean peak enhancement of abdominal aorta in normal and the liver cirrhosis group were 196.40 Hu ±20 Hu and 186.02 Hu ±18 Hu respectively,P>0.05;arterial phase average trigger time of normal group and cirrhosis group was 22 seconds and 24 seconds respectively,P<0.05.When the injection rate of contrast medium was 3.5 mL/s,the mean peak enhancement of abdominal aorta in normal group and cirrhosis group were 244.90 Hu ±37 Hu and 219.33 Hu ±33 Hu respectively,P<0.05;the average trigger time of arterial phase in normal group and the liver cirrhosis group was 20 seconds and 22 seconds respectively,P<0.05.Conclusion: The injection rate of contrast medium is faster,the arterial phase peak is higher,the triggering time is shorter.In the same injection rate,the mean peak enhancement of abdominal aorta of normal group is higher than that of cirrhosis group,and the average trigger time is shorter than that of cirrhosis group.Liver cirrhosis group needs higher speed on injection than normal group.