Abstract:

Objective　To explore the anatomical variation and classification of Willis ring in the southern Guizhou province, and to provide a control for the cerebrovascular diseases of ethnic minorities in Qiannan area.　Methods　In this study, retrospective study was carried out continuously in the Qiannan People's Hospital from December 2011 to February 2017. CT and MRI were normal and CTA was used to check the 513 of the Buyi or Miao adults in Qiannan. The data were examined by Siemens signo workstations, row VR, MIP and MPR，multi-modal and multi-angle observation of the Willis ring development were used for classification and type analysis.　Results　According to the development of arterial arteries, 513 cases of normal cerebral artery Willis ring were divided into four types, typeⅠ3.7% (19 cases), typeⅡ0.1% (5 cases), and type Ⅲ 65.5% (336 cases), according to the development situation of the posterior circulation is divided into 5 subtypes: IIIa 18.9% (97 cases), IIIb 32.2% (165 cases), IIIc 2.5% (13 cases), Ⅲd 4.5% (23 cases), Ⅲe 7.4%(38 cases) and  Type IV 29.8% (153 cases); according to the development situation before and after the circulation of type IV combination will be divided into 5 subtypes: IVa 21% (108 cases), IVb 1.2% (6 cases), IVc, 1.6% (8 cases), IVd, 1.9% (10 cases), and  IVe, 4.1% (21 cases).　Conclusion　CTA is a noninvasive and effective method for evaluation of the basilar artery type. It is possible to evaluate the basilar artery ring in the Qiannan area by CTA. It can provide normal control for other diseases related to cerebrovascular type. The symmetrical type Willis ring display rate is low, whereas type Ⅲ is the main type followed by type Ⅳ.

Key words: CT angiography（CTA）, 　Cerebral vascular types, 　 Ethnic regions, 　Willis ring