1. From the Departments of Radiology (M.H.L., R.Z., J.W.G., P.M.G., P.J.P.) and Medical Physics (J.W.G.), University of Wisconsin School of Medicine and Public Health, 600 Highland Ave, Madison, WI 53792; and Imaging Biomarkers and Computer-Aided Diagnosis Laboratory, Radiology and Imaging Sciences, National Institutes of Health Clinical Center, Bethesda, Md (R.M.S.).