Abstract: Objective  To investigate the development and variation of cerebral artery ring (Willis ring) in patients with cerebral vascular disease. Methods  MRA 3DTOP images of 100 patients with cerebral vascular disease were analyzed， and the variation and incidence of each artery were  analyzed and compared with the MRA 3DTOP images of 100 healthy people. Results  There was a large variation in Willis ring between two groups. Willis ring development complete rates of hospitalized patients and healthy checkup people were 13% and 25%， respectively. There was statistically significant difference between two groups (P<0.05). Conclusion  The incompleteness of Willis ring is closely related to the occurrence of cerebrovascular disease.

Key words: brain ischemia, circle of , Willis, magnetic resonance imaging