Objective:To explore the imaging characteristics and clinical value of CT angiography (CTA) of the aorta in active arteritis.Methods:A retrospective analysis was conducted on the clinical data and laboratory examination results of 77 patients with Takayasu arteritis (TAK) admitted to the Rheumatology and Immunology Department of People′s Hospital of Xinjiang Uygur Autonomous Region from January 2015 to October 2022. They were divided into two groups: 62 cases in the TAK active group and 15 cases in the TAK inactive group. Among them, 17 patients were followed up, 13 cases became inactive, and 4 cases remained active. A total of 94 aortic CTA imaging results were divided into 2 groups, with 66 cases in the TAK active group and 28 cases in the TAK inactive group.All patients underwent plain chest and abdominal CT scans, aortic CTA, and post-processing examinations, with 12 active TAK patients undergoing delayed aortic enhancement scans. The t-test, Mann Whitney U test, χ2 Testing, Fisher′s exact probability method and Pearson/Spearman correlation analysis were used for data analysis. The imaging features of the two groups were measured and compared, the correlation between imaging features and laboratory results, Kerr score were investigated. The diagnositic efficacy of imaging features were explored and imaging features before and after treatment were analyzed. Results:In the TAK active and inactive groups, course of disease[14 (1, 29) months vs 33(8, 69)months, Z=2.70, P=0.007], Physical malaise or weight loss[32.3%(20/62) vs 20.0%(3/15), χ2=4.08, P=0.043], increased ESR [98.4% (61/62) vs 13.3% (2/15)], χ2=64.69, P<0.001], CRP level[69.4% (43/62) vs 6.7%(1/15), χ2=29.94, P<0.001] were statistically significant. The vascular wall thickness of the two groups was significantly different [(4.2±1.4)mm vs (2.4±0.8)mm, t=7.81, P<0.001], CT mean value of the garterial wall [(81±8) Hu vs (70±13)Hu, t=2.82, P=0.011], CT max value of the arterial wall [(106±12)Hu vs (96±12)Hu, t=2.38, P=0.024], relative CT value 1 of the arterial wall (0.20±0.08 vs 0.14±0.04, t=2.56, P=0.016), relative CT value 2 of the arterial wall (1.23±0.18 vs 1.06±0.17, t=2.63, P=0.013), CT mean value of periaortic adipose tissue [(-31±12)Hu vs (-58±20)Hu, t=4.80, P<0.001)], CT max value of periaortic adipose tissue [-35(-45,-25)Hu vs -87(-95, -42)Hu, Z=4.27, P<0.001], CT mean value of adipose tissue around branches[-28(-33, -14)Hu vs -76(-83, -31)Hu, Z=3.37, P=0.001], CT max value of adipose tissue around branches[-7(-13,-1)Hu vs -59(-72, -14)Hu, Z=3.74, P<0.001], relative CT values of adipose tissue around the aorta (0.26 ± 0.09 vs 0.51 ± 0.19, t=4.47, P<0.001)], relative CT values of adipose tissue around branches (0.17 ± 0.09 vs 0.28 ± 0.18, t=2.35, P=0.025) were significant different. The wall thickness value, relative CT value of periaortic adipose tissue, and CT mean value of periaortic adipose tissue had high diagnostic efficacy, with cut-off values of 3.25 mm, 0.455, and -55 Hu, respectively. The AUCs were 0.911, 0.887, and 0.863, respectively. The Youden index was 0.687, 0.730, and 0.715, respectively. The sensitivity and specificity were 0.758 and 0.929, 0.909 and 0.821, 0.894 and 0.821, respectively. After treatment, 11 active TAK patients became inactive, with reduced wall thickening, enhancement, and density of perivascular adipose tissue. Thirteen patients with active TAK underwent delayed aortic enhancement scanning, and it was found that the low-density loop sign of the aortic intima was more clearly displayed during this period, and the enhancement amplitude of the vascular wall tended to be uniform. Conclusion:Aortic CTA is an effective method for qualitative evaluation of TAK activity.