Radioisotope Research Center, Agency of Health, Safety and Environment, Kyoto University, Kyoto, Japan. Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan. Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan. Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan. Research and Development Division, Arkray, Inc., Kyoto, Japan. Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, Kyoto, Japan.