1 From the Department of Radiology, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114-2696 (H.A.); Department of Radiology, University of Washington, Seattle, Wash (P.K.); Department of Radiology, University of Alabama at Birmingham, Birmingham, Ala (M.N.); and Department of Radiology, University of California San Diego, San Diego, Calif (M.H.).