1. From the Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd, St Louis, MO 63110 (K.M.M., C.A.R., M.Z.R., K.L.S., D.D.P., S.B.); Department of Radiology, University of California–San Francisco, San Francisco, Calif (T.S.H.); and Department of Radiology, Centro Rossi, Buenos Aires, Argentina (S.E.R.).