1 From the Division of Vascular and Interventional Radiology (K.W.) and Division of Neuroradiology (J.B.), Department of Radiology, Montefiore Medical Center, 111 E 210th St, Bronx, NY 10467; Division of Vascular and Interventional Radiology, Russell H. Morgan Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Md (T.G.); and Department of Radiology, University of Alabama at Birmingham, Birmingham, Ala (C.A.W.).