1. From the Departments of Radiology (M.Y., K.J.G., A.M., R.L.E.) and Physiology and Biomedical Engineering (A.M.) and the Divisions of Anatomic Pathology (T.M.), Gastroenterology and Hepatology (H.M., D.A.S., R.W., L.Y., V.H.S.), Transplantation Surgery (S.A.M., J.M.G., F.M.E., S.L.N.), and Nephrology and Hypertension (C.J.W., P.C.H.), Mayo Clinic, 200 First St SW, Rochester, MN 55905.