Abstract: Objective: To explore the feasibility of contrast medium's best injection combined with low tube voltage in aortic CTA.Methods: Divided 80 patients who will be done aortic CTA examination into A, B two groups(n=40) by different contrast medium concentrations and tube voltages, while group A is divided into group A1, group A2(n=20) by different contrast medium concentrations and injection rate.Group A1: Injecting 302 mg I/mL Iohexol as contract medium, injection rate 4 mL/s, tube voltages 100 kV;group A2: Injecting 300 mg I/mL Iohexol as contract medium, injection rate 3.5 mL/s, tube voltages 100 kV;group B: Injecting 350 mg I/mL Iohexol as contract medium, injection rate 3.5 mL/s, tube vantage 120 kV;Other scanning parameters: Injection contrast dose, reconstruction mode, automatic tube current regulation technologies are consistent.Two independent sample tests are used(Mann-Whitney U test for non-normal distribution) to compare the clinic data, radiation dose of CT, subjective and objective evaluation of image quality in the two groups.Results: There was no significant difference in age, gender, body mass index(BMI) between group A and group B(P>0.05);there was also no statistical significance in the subjective and objective evaluation of image quality(P>0.05).The CNR of group B was better than group A, which met the diagnostic requirements, the CT values of the aortic trunk and branches were all>300 HU.There was statistically significant differences between group A and group B in radiation dose and iodine content(P<0.01).Effective radiation dose(ED) of group A was 17.73%lower than that of group B, and iodine content was 14.29%lower.Conclusion: injection of 300 mgI/mL Iohexol solution and injection rate of 3.5 mL/s combined with low tube voltage(100 kV) obtained satisfactory image quality in aortic CTA examination, providing accurate diagnostic basis for clinical practice, which not only reduced the radiation dose, but also reduced the iodine content.