Objective:Comparison of different scanning and injection protocols for bronchial artery CT angiography(CTA). Methods:Eighty cases scheduled for bronchial artery CTA were randomly assigned into four groups according to the injection protocol. Cases in group 1 to group 3 adopted the injection rate of 4, 5 and 6 ml/s respectively, and used automatic threshold preset at 300 HU to trigger the initiation of the scan, with total contrast dose of 1.5 ml/kg body weight. Cases in the group 4 adopted an injection rate of 6 ml/s, triggering threshold of 120 HU, and 1.0 ml/kg body weight of contrast. High density contrast(350 mgI/ml)was used in all cases. The CT values of pulmonary artery, superior vena cava, aortic artery and bronchial artery before and after enhanced scanning were measured in the 4 groups. Numbers of cases with excellent image quality of bronchial artery display were also evaluated. Results:The CT values of pulmonary artery and superior vena cava among four groups hadn’t significant difference(P > 0.05). The CT values of aortic artery in group 4 were higher than other three groups significantly(P < 0.05). The CT values of bronchial artery in group 4 were higher than group 1 and group 2 significantly (P < 0.05). The excellent rate of bronchial artery CTA for group one to group four were: 50%, 55%, 65% and 80%, respectively. Conclusion:This research showed that the injection rate of 6 ml/s, triggering threshold of 120 HU, 1.0 ml/kg body weight of high density contrast dose provide higher contrast,and it’s on optimal protocol for bronchial artery CTA.