Objective To explore the clinical application of 80 kVp tube voltage combined with low dose and low concentration contrast agent in CT imaging of renal artery (CTA) in elderly patients.Methods 160 elderly patients undergoing CT angiography of renal artery or abdominal aorta in our hospital from August 2016 to June 2017 were randomized to control group (routine-dose CT with 120 kVp at 120 mAs,contrast agent of 70 ml,n=40) and double low group (X ray tube voltage at 80 kVp and contrast agent of 50 ml),which was re-divided to double low-150 mAs group,double low-180 mAs group,and double low-210 mAs group (n=40,each).The CT value of bilateral renal arteries,their branches,and abdominal aorta at the same height of renal artery,signal to noise ratio (SNR),contrast to noise ratio (CNR),the effective radiation dose,and the incidence of adverse reaction were measured after sinogram-affirmed iterative reconstruction (SAFIRE).And the image quality was evaluated and rated on a scale from 1 to 5 by two independent qualified radiologists.Results The vascular enhancement was significantly higher in the three double low groups than in the control group (all P＜0.05).Noise level was higher in the three double low groups than in the control group (all P＜0.05).SNR and CNR showed no significant difference between the double low-210 mAs group and the control group (P＞0.05),while statistical differences were found in SNR and CNR in the control group versus double low-150 mAs and double low-180 mAs groups (all P＜0.05).As compared with the control group,effective radiation dose was decreased in the three double low groups by 63.3％ (150 mAs),56.2％ (180 mAs),48.8％ (210 mAs),respectively.All image scores in four groups were over 3 points.Mild adverse effects were observed in four cases from the control group,and no adverse effect occurred in the other three groups.Conclusions 80 kVp tube voltage combined with low dose and low concentration contrast agent can appropriately increase tube current.Combined with SAFIRE,it can not only help maintain image quality,but also decrease the damage of organs by reducing the doses of radiation and contrast agent.