1. From the Division of Vascular and Interventional Radiology, Department of Radiology, University of North Carolina at Chapel Hill, 2016 Old Clinic, CB 7510, Chapel Hill, NC 27599 (H.Y., A.J.I., C.T.B.); Department of Radiology, University of North Carolina School of Medicine, Chapel Hill, NC (L.M.B.B.), Department of Surgery, Massachusetts General Hospital, Boston, Mass (J.S.E.).