1. From the Department of Radiology, Massachusetts General Hospital, Boston, Mass (M.E.T.); Departments of Interventional Radiology (N.K., G.S.) and Radiology (M.K.), University of North Carolina School of Medicine, 101 Manning Dr, CB 7510, Chapel Hill, NC 27599; and Division of Vascular and Interventional Radiology, University of Alabama at Birmingham, Birmingham, Ala (T.C.).