1 From the Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, GRB 273, Boston MA 02114 (F.D., S.I.L.); Department of Radiology, New York University School of Medicine, New York, NY (E.K.); and Department of Radiology and Imaging Sciences, Emory University School of Medicine, Emory University Hospital, Atlanta, Ga (A.V.T.).