1. Hitachi Medical Co. chaired Department of Diagnostic and Interventional Imagiology, Department of Nuclear Medicine and Diagnostic Imaging, and Department of Radiology, Kyoto University, Kyoto 606-8507, Japan, Department of Radiology, Otsu Municipal Hospital, Otsu 520-0804, Japan, and Chemistry Section, Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892