ObjectiveTo explore the clinical value of low-dose contrast agnet in CT angiography (CTA) for head and neck by SOMATOM Definition Flash CT.MethodsSixty consecutive patients with head and neck vessel diseases examined by CTA in the head and neck were chosen from West China Hospital of Sichuan University from March to July 2015, and then were randomly divided into two groups (the experimental group: n=30, 30 mL contrast medium; the control group: n=30, 50 mL contrast medium). Imaging post processing techniques included curved plannar reconstruction, volume rendering, and maximal intensity projection. CT values of the different level of carotid arteries (aortic arch, carotid bifuracation, and M1 segment of middle cerebral artery) were measured. The artifact of the remaining contract in the jugular vein and overall quality of the image were observed by two senior doctors using double blind method.ResultsAll the patients in the two groups completed CTA for head and neck successfully. The image qualities of the two groups satisfid clinical diagnostic requirements, and there was no difference in the image qualities between the two groups (P>0.05). The evaluation of venous pollution in the experimental group was lighter than that in the control group (P<0.05). The CT values of aortic arch, carotid bifuracation, and M1 segment of middle cerebral artery in the experimental group [(341.3±89.5), (391.0±103.7), (305.0±62.0) HU] were slightly lower than those in the control group [(437.3±83.7), (532.5±113.3), (396.6±93.1) HU], which were statistically significant (P<0.05).ConclusionLow-dose contrast in CTA for head and neck by SOMATOM Definition Flash CT can satisfy the clinical diagnostic requirements, and reduce the dose of contrast agent and venous pollution, with a good clinical value.