1. From the Departments of Surgery (J.W.J.), Radiology (G.K.H., M.W.U., C.U.L.), Quantitative Health Sciences, Division of Clinical Trials and Biostatistics (N.B.L.), Orthopedic Surgery (M.J.Y., A.L.M.), and Physiology and Biomedical Engineering (J.F.G., M.W.U.), Mayo Clinic, 4500 San Pablo Blvd, Jacksonville, FL 32224.