1. From the Biomedical and Metabolic Imaging Branch, National Institute of Diabetes and Digestive and Kidney Diseases (K.Z.A.E., H.I., J.M., A.H., A.M.G.), Critical Care Medicine Department, National Institutes of Health Clinical Center (J.P.), National Human Genome Research Institute (H.H.), and National Institute of Allergy and Infectious Diseases (C.H.), National Institutes of Health, 10 Center Dr, Bethesda, MD 20892; and Department of Radiology, University of Chicago, Chicago, Ill (A.H.).