1. From the Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd, Box 8131, St Louis, MO 63110 (H.L.P.O., S.M., V.M.M., S.B.); Department of Radiology, University of Wisconsin, Madison, Wis (M.G.L., P.J.P.); and Department of Radiology, Mayo Clinic, Scottsdale, Ariz (C.O.M.).