1. From the Department of Radiology, Mayo Clinic, 4500 San Pablo Rd, Jacksonville, FL 32224 (D.J.D., J.I.L., J.G.C.); Department of Radiology, Mayo Clinic, Scottsdale, Ariz (C.O.M.); Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Mo (D.M.B.); and Department of Radiology, University of Alabama at Birmingham, Birmingham, Ala (D.E.M.).