1. From the Departments of Radiology (S.H., H.H., T.N., Y.O., T.F.) and Cardiovascular Medicine (T.A., J.U., A.T., T.O.), National Cerebral and Cardiovascular Center, 6-1 Kishibeshinmachi, Suita, Osaka 564-8565, Japan; and Department of Diagnostic Radiology, Tohoku University Hospital, Sendai, Japan (S.H., H.O.).