The purpose of this research study is to evaluate adult children of parents with and without Alzheimer's disease which represent an ideal population for investigating the biological changes that precede the clinical onset of AD. The investigators will be imaging the brain to detect the presence of amyloid deposits (plaques in the brain). Amyloid is a protein that may be related to dementia of Alzheimer's disease (DAT).

This study will use a radioactive tracer called [11C]-Pittsburgh Compound B (11C]PIB), which is a tracer that binds to beta amyloid protein in the brain. This compound is considered investigational, which means that it has not been approved by the United States Food and Drug Administration (FDA).

Inclusion Criteria:

• Male or female, any race;
• Age ≥ 18 years;
• Active participants currently enrolled in the Knight Alzheimer's Disease Research Center (ADRC) at Washington University.

Exclusion Criteria:

• Hypersensitivity to [11C] PIB or any of its excipients;
• Contraindications to PET, CT or MRI (e.g. electronic medical devices, inability to lie still for extended periods) that make it unsafe for the individual to participate;
• Severe claustrophobia;
• Women who are pregnant or breast-feeding will be excluded from PIB PET participation;
• Has any condition that, in the opinion of the Sponsor-Investigator or designee could increase risk to the subject, limit the subject's ability to tolerate the research procedures, or interfere with collection of the data;
• Currently participating in any clinical trial which involves an active study medication or placebo within the past 30 days before scanning and up to 2-weeks past the imaging visit.
• Current or recent (within 12 months prior to screening) participation in research studies involving radioactive agents such that the total research-related radiation dose to the participant in any given year would exceed the limits set forth in the U.S. Code of Federal Regulations (CFR) Title 21 Section 361.1. https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=361.1

Active participants currently enrolled in the Knight Alzheimer's Disease Research Center (ADRC) at Washington University.