1. From the Department of Radiology, Harvard Medical School, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114 (C.A.B.); Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Conn (N.S.); Department of Radiology, University of Alabama at Birmingham, Birmingham, Ala (M.N.); and Department of Radiology, Hospital Militar Central, Bogota, Colombia (F.C.).