Investigation of Inflammation in Alzheimer's Disease and Related Dementias (ADRD) Using [11C]-CS1P1

Inclusion Criteria: * Male or female, any race; * Age ≥ 50 years; * Capable of providing written informed consent OR having a legally authorized representative (LAR) to provide informed consent for volunteering to undergo research procedure; * Additional inclusion for ADRD group: clinical diagnosis of mild cognitive impairment or early dementia due to ADRD, OR biomarker diagnosis of Alzheimer's disease, with or without symptoms. Exclusion Criteria: * Hypersensitivity to \[11C\]-CS1P1 or any of its excipients; * Contraindications to PET, CT, or MRI (e.g. certain incompatible electronic medical devices, inability to lie still for extended periods) that make it potentially unsafe for the individual to participate; * Severe claustrophobia; * Women who are currently pregnant or breast-feeding; * Currently undergoing radiation therapy; * Any condition that, in the opinion of the Sponsor-Investigator or designee could increase risk to the participant, limit the participant's ability to tolerate the research procedures or interfere with collection of the data (e.g., renal or liver failure, advanced cancer); * Participants who in the last 6 months experienced any of the following cardiovascular conditions or findings in the screening electrocardiogram (ECG): clinically significant cardiac arrhythmias including high grade heart block (type 2 or greater), unstable angina, or decompensated heart failure requiring hospitalization or Class III/IV heart failure; * Moderate to Severe anemia with Hemoglobin \< than 9.9 in both males and females. * 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