1. From the Department of Radiology and Diagnostic Imaging, University of Alberta, 2B2.41 WMC, 8440-112 St NW, Edmonton, AB, Canada T6G 2B7 (M.P.W., D.P., P.K., G.L.); Evidence-based Practice Center, Mayo Clinic, Rochester, Minn (M.H.M.); and Departments of Radiology and Epidemiology, University of Ottawa/The Ottawa Hospital Research Institute, Ottawa, Canada (M.D.F.M.).