Inclusion Criteria:  Enrolled in the Health and Aging Brain Study HD: Health Disparities project Provided consent to re-contact Willing and capable of undergoing PET scan of the head  Exclusion Criteria:  Inability to provide informed consent by self or by proxy. Pregnant or breast feeding women* History of alcoholism or drug dependency/abuse within the last 2 years before screening Hypersensitivity to the active substance or to any of the following excipients is contraindicated: sodium dihydrogen phosphate, phosphoric acid, sodium ascorbate, ethanol (anhydrous), water for injection Participants may not be in this study if they do not meet the safety criteria to undergo imaging procedures.