Objective To study the feasibility of abdominal aortic CT angiography with low dose contrast medium.Methods The patients who took the examinations were divided into three groups.In 34 patients of group A,the injection flow rate was 4 ml/s,and the contrast medium volume was 90 ml and 20 ml of saline was applied.The contrast medium dose and injection flow rate of the other 64 patients were determined according to the formula,injection tlow rate = patients' body mass × ratio of contrast medium dose to the body mass / (5 + exposure time).In B and C group with 32 cases each,the ratio of contrast medium dose to body mass were 0.8 to 0.9 and 0.6 to 0.7 ml/kg.The depiction and the measured intraarterial concentration of contrast medium of the abdominal aorta and the renal arteries as well as their branches were compared and evaluated on the source images and MIP images generated among three groups respectively.CT values of the abdominal aorta and its branches in each group were analyzed using singlefactor analysis of variance,while renal artery and its branches were analyzed using x2 test score.Results The abdominal aorta,the celiac trunk,the splenic artery,the superior mesenteric artery,the renal arteries and their branches were all well shown in three groups.The CT value within the abdominal aorta were (363 ±28),(362 ±28) and (334 ± 14) HU for the three groups respectively,the CT values within the celiac were (368 ±28),(367 ±28) and (338 ± 15)HU,the CT value within the renal artery were (365 ±27),(364 ± 29) and (336 ± 15) HU respectively,the CT value within the splenic artery were (373 ±28),(372 ± 28) and (343 ± 15) HU respectively,and the CT value within the superior mesenteric artery were ( 374 ± 28 ),( 372 ± 28 ) and ( 344 ± 16 ) HU respectively.There were significant differences among the three groups ( P = 0.000).There were significant differences between A group and C group,B group and C group ( P ＜ 0.01 ),while no significant difference existed between A group and B group( P ＞0.05 ).The amount of contrast agent for each patient in group A was 90 ml,while the amount of contrast agent in group B and C was (51 ± 9) and (40 ± 9) ml respectively.There were significant differences of the contrast medium volume among the three groups ( F = 537.091,P = 0.000).Results of pairwise comparisons were statistically significant(P =0.000).Image quality of renal artery in group A was rated as excellent,good,and generally for 26,7 and 1 cases,24,7 and 1 for group B,and 22,8 and 2 for group C.There were no significant differences in image quality of the renal arteries among the three groups ( x2 = 0.561,P = 0.755 ).Conclusion The individualization of injection method in abdominal aortic CT angiography can minimize the amount of contrast agent but to meet the clinical requirements.