A Direct Comparative Study of Tau Tracer in Patients With Alzheimer's Disease

Patients with AD in prodromal stage, mild or moderate degree, who have stable medical condition and meet the inclusion criteria, do not meet any exclusion criteria, will be eligible for inclusion in this study. \[18F\] florbetapir PET imaging will be used to evaluate amyloid deposition during the screening period. If \[18F\] florbetapir imaging confirmed amyloid deposition based on positive visual reading and SUVR \> 1.1, the patient was considered to be amyloid deposition positive.After the subjects enter the group, the comprehensive collection of clinical information, the assessment of cognitive related scale and the collection and detection of biological samples are carried out. Qualified subjects will complete PET imaging scan of Tau imaging agent in Xuanwu Hospital, and each subject will receive three of the following five imaging agents: PI-2620, APN1607, AV1451, RO948 or GTP1. All subjects will sign the tracer related informed consent before PET tracer injection. Imaging will be carried out as detailed in the technical operation manual. PET center staff will closely observe and evaluate adverse events of subjects throughout the process, and allow them to leave the hospital after confirming medical stability. After 48 hours of scanning, the staff will follow up the subjects by telephone to confirm the health status of the subjects and record the information related to adverse events. The imaging time interval between the two tracers should be at least 4 days but less than 4 weeks. All PET scans of each subject were completed within 3 months.