1. From the Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce St, 1 Silverstein Place, Philadelphia, PA 19104 (S.P.Z., E.F.C.); and Departments of Surgery (B.L.S.), Pathology (D.L.W.), and Radiology (S.D.H.), University of Vermont, University of Vermont Cancer Center, Burlington, Vt.