Neuroimaging in Healthy Aging and Senile Dementia (HASD_IND)

Who May Qualify: - Male or female, any race - Age \> 18 years - Participation in one of the ongoing projects affiliated with the Knight ADRC at Washington University and referred by the MAP staff and a Washington University physician. - Normal cognition or early-stage symptomatic AD - Willing and able to undergo study procedures. - Capacity to give willing to sign a consent form and follow study procedures Who Should NOT Join This Trial: - Has any condition that, in the Investigator's opinion, could increase risk to the participant, limit the participant's ability to tolerate the research procedures, or interfere with the collection/analysis of the data (e.g., participants with severe chronic back pain might not be able to lie still during the scanning procedures); - Has hypersensitivity to either AV-1451 or 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; - Currently pregnant or breast-feeding. Women must agree to avoid becoming pregnant and must agree to refrain from sexual activity or to use reliable contraceptive methods for 24 hours following administration of Flortaucipir injection; - Must not have participated in any clinical trial involving a study drug or device within the 30-days prior to study enrollment; - Must not participate in another drug or device study prior to the end of this study participation; - 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 Always talk to your doctor about whether this trial is right for you.