Amyloid PET Imaging in the Baltimore Longitudinal Study of Aging

* INCLUSION/EXCLUSION CRITERIA: * Participants are men and women 55 years and older drawn from the BLSA sample and thus, represent the gender/ethnic characteristics of this study group. Enrollment is defined as the initial imaging session of the planned longitudinal study. * Inclusion criteria: BLSA participants who do not meet exclusion criteria and have had or agreed to have an MRI under the BLSA study. * Participants who lack capacity to consent will not be enrolled in the study. If the participant loses capacity to consent over the course of follow-up they will be removed them from the study. Competency to consent is assessed as part of the BLSA visit and we will not include people who are not competent to provide consent. EXCLUSION CRITERIA: * Preexisting central nervous system diseases * Weight over 300 lbs. * Active metastatic cancer (except basal cell cancer) * Implanted electronic hearing devices * Breast Cancer with radiation treatment * Lymphoma * Pacemaker * Brain tumor * Shrapnel * Schizophrenia * Bipolar disorder * Epilepsy * Language barrier that makes it difficult to understand participant. * Aneurisms greater than 3mm * Aneurysm clips * Parkinson s disease/PD medications * Huntington s disease * Severe Endocrinopathy- treated thyroid conditions ok; treated, controlled diabetes ok. (exclude HbA1c over 8 which is poorly controlled diabetes) * Diagnosis of dementia or mild cognitive impairment * Younger than 55 years of age * Pregnancy * Ineligible for MRI * History of stroke or documented TIAs requiring hospitalization * Known brain vascular malformations or adenomas * History of significant radiation exposure * Those with a Blessed score of 4 or more with the BLSA will be reviewed at a research diagnostic case conference to rule out dementia diagnoses prior to enrollment.