1. From the Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd, Campus Box 8131, St Louis, MO 63110 (K.M.S.); Department of Radiology, University of Texas Health Science Center San Antonio, San Antonio, Tex (A.K.S.); and Department of Radiology, University of Iowa College of Medicine, Iowa City, Iowa (S.C.K.).