1. From the Department of Radiology (T.J.A., E.B., P.G.K.) and Department of Biostatistics and Bioinformatics (R.L., S.L.), Duke University Medical Center, Box 3808, Box 3850 Durham, NC 27710; Department of Radiology, University of Pittsburgh Medical Center, St. Margaret Hospital, Pittsburgh, Pa (S.V.); and Department of Radiology, University of North Carolina–Chapel Hill, Chapel Hill, NC (P.P.).