1. From the Department of Neurosurgery (Z.M., L.J., H.W., Y.B., L.J., J.Z., F.L.), Center for interventional diagnosis and treatment (S.L., F.Z.), Departments of Neurology (J.W.), Vascular Ultrasonography (Y.H.) and Radiology (Y.L.), Xuanwu Hospital, Capital Medical University, Beijing, China; and Institute of Biomedical engineering, Capital Medical University, Beijing, China (X.L.).