1. From the Department of Radiology (W.M.V., S.P.S., M.C.W., J.G.F.), Department of Surgery (A.L.L.), and School of Medicine (S.T.K.), Mayo Clinic, 200 First St SW, Rochester, MN 55905; and Department of Radiology, Mayo Clinic, Scottsdale, Ariz (C.O.M.).