1. From the Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, WAC 240, Boston, MA 02114 (C.D.L.); Group Health Research Institute, Group Health Cooperative, Seattle, Wash (R.F.A., D.S.M.B.); Department of Surgery, University of Vermont College of Medicine, Burlington, Vt (B.L.S.); Department of Radiology, University of Washington School of Medicine, Seattle, Wash (J.M.L.); Department of Medicine, Epidemiology and Biostatistics, University of California–San...