Purpose 1.carotid stenosis is a common cause of ischemic stroke. our purpose is to analyze the morphologic and hemodynamic character of extracranial carotid vessel intensively, which can be the rationale for clinical revascularization. 2.surgical treatment for carotid stenosis include carotid endarterectomy (CEA) and carotid artery stenting (CAS). the surgical indication, surgical method and complication are compared primarily. and by the observation of the change in CT perfusion imaing parameters before and after operation, the effects in hemodynamic state inserted by two kind of operation are compared. Data and Method 1.there are 213 cases of internal carotid artery stenosis in beijing xuanwu hospital and beijing tiantan hospital during 2000~2004, using angiography to evaluate collateral flow characters of vessels, and using CT perfusing –Imaging parameter to evaluate hemodynamic character of cerebral perfusion, combined with clinical history. the stenosis degree, collateral flow and CT-perfusion Imaging parameter were analyzed intensively. 2. There are 120 cases of CAS and CEA in beijing xuanwu hospital and beijing tiantan hospital during 2000~2004, the surgical indication and peri-operaional in-advanted incidence are compared individually, and the patients receive CT perfuison imaging examination before and after operaion, CTPI parameter in the region of middle cerebral artery are obtained and compared, the control analysis of TTP in the rigion of interests are finished. Result 1.Willis circle and PCA leptomeningeal anastomosis is the dominant collateral circulation, which can increase with the progress of stenosis degree, when carotid stenosis or occlusion lesion is at one side. The risk of stroke have no direct relations with degree of carotid stenosis. Whereas, in the cases with serious stenosis, if the collateral circulation is abundant,it will have lower risk of stroke. Among all the type of collateral circulation, the combination of anterior communicating artery and posterior communicating artery is best, anterior communicating artery alone is second one, the function of posterior communicating artery is limited. 2. In case of bilateral carotid stenosis or occlusion, the summary of different type collateral circulation is common, Willis circle compensation alone is rare, but in the case of occlusion at one side,and stenosis at the contralateral side,the anterior communicating compensation is common,and the stroke usually occurred at the stenosis side.and if the posterior communicating artery appear, the infarction incidence is lower. 3. There are no difference of regional cerebral hemodynamic between different stensis degree group.due to the vascular reaction itself or collateral compensation.but the TTP is prolonged, which means cerebral-vascular circulation reserve damaged. 4. Two kind of operation for revascularization have little effects on the regional cerebral blood flow.but the TTP is shortened.CAS have fewer complication at the perioperational period,and have wider indication,but the indication for CEA need to be controlled strictly. Conclusion