Abstract: Objective:To investigate the of dual-phase enhanced scanning technology in pulmonary angiography(PA) and bronchial angiography(BA).Methods:One hundred and twenty scanned by chest enhanced 64-slice spiral CT from the Second Affiliated Hospital of Suzhou University were selected.The fixed delay method and bolus tracking(BT) method were employed.The patients treated with fixed delay method were divided into the group A(injected with 80mL contrast agent,delay scanning for 14 s in PA phase and delay scanning for 20s in BA phase),groupB(injected with 80mL contrast agent,delay scanning for 14s in PA phase and delay scanning for 22s in BA phase),and group C(injected with 70mL contrast agent,delay scanning for 12s in PA phase and delay scanning for 22s in BA phase).Among the patients treated with Bolus Tracking(BT),the same slice was tracked and scanned after 3s of 70mL contrast agent injecting.The crotch of the pulmonary artery trunk was the interest region,the scan was launched after the CT value achieved 100Hu threshold.The target vascular enhancement value was evaluated,and the difference of which was compared.Results:Among the patients treated with fixed delay method,the reinforced difference values of PA/DA in PA phase and BA phase in group C were(243±111)Hu and(248±73)Hu,respectively,and the difference of the density in group C was significantly higher than that in group A and group B.In PA phase,the difference value of PA/DA in group C was higher than that in group A and group B(P<0.05 and P<0.01),the CT values of superior vena cava(SVC) in group B and group C were higher than that in group A(P<0.05 and P<0.01),the CT values of ascending aorta(AA) and descending aorta(DA) in group C were significantly lower than those in group A and group B(P<0.05 to P<0.01),and the CT value of left atrium(LV) was lower than that in group A and group B(P<0.05).In BA phase,the differences of the CT values of SVC,PA,LV and AA between group A and group B were statistically significant(P<0.05),the CT values of SVC,LV and AA in group C were significantly lower than those in group A and group B(P<0.05 to P<0.01),the differences of the CT values of SVC,LV and AA between groups A and B were not statistically signficant(P>0.05),and the contrast agent in group C decreased.Among the patients treated with bolus tracking(BT) method,the reinforced difference values of PA/DA in PA phase and BA phase in group C were (241±97)Hu and (234±60)Hu,respectively,and the difference of which between two methods was not statistically significant(P>0.05).Conclusions:The good images of CTPA and CTBA can be acquired using the fixed delay method or bolus tracking method at one check,and the fixed delay method or bolus tracking method is a two-phase imaging technology,which can identify the density difference of PA and BA.The bolus tracking method has advantage over the fixed delay method in individualized examination.