1. From the Department of Imaging Physics (M.C.J., C.A.W., D.D.C.), Department of Diagnostic Radiology, Sections of Neuroradiology (D.S.), Abdominal Imaging (E.P.T.), and Thoracic Imaging (M.C.G.), and Department of Biostatistics (J.S.), The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030.