PROCEDURES: Informed consent, collection of demographic information and medical history, administration of mental status exam, physical examination, vital signs, 12-lead ECGs, routine blood tests to assess major organ functions, complete blood counts and clinical chemistries for safety, dosing with [F-18]W372, PET imaging scans of brain (in sixteen subjects), whole body PET imaging and urine collections for dosimetry evaluation (in four subjects only), observation and interviews following imaging to collect adverse events.