Florbetazine[18F]

1) Evaluate the safety of 18F fluorobenazine injection in AD patients, MCI patients and healthy subjects. 2) Detect the pharmacokinetics of 18F fluorobenazine injection in healthy subjects. 3) Detect the biodistribution of 18F fluorobenazine injection in healthy subjects and estimate the internal radiation absorbed dose. 4) Detect the metabolic stability of 18F fluorobenazine injection in healthy subjects. 5) Evaluate the standard uptake value 6 (SUVR) of 18F fluorobenazine injection in the brain (cerebrum and cerebellum) of AD patients and MCI patients. 7) Evaluate and compare the brain uptake pattern of 18F fluorobenazine injection in AD patients and MCI patients. 8) Evaluate the reproducibility of in vivo imaging of 18F fluorobenazine injection in AD patients and MCI patients. 9) Evaluate the effect of 18F fluorobenazine injection dosage on image quality in AD patients and MCI patients.