Evaluate the Concordance Between PET Imaging of [18F]-APN-1607 Injection and Postmortem Brain Tissue Tau Pathology in Individuals With HV and MCI or AD.

1. To evaluate the diagnostic performance of \[18F\]-APN-1607 injection PET imaging in detecting uptake patterns consistent with AD neuropathological changes as defined by the National Institute on Aging-Alzheimer's Association (NIA-AA) criteria. 2. To assess the association between \[18F\]-APN-1607 injection and Alzheimer's disease (AD)-related tau neurofibrillary pathology (as determined by post-mortem brain tissue histopathology), and detect the uptake pattern corresponding to neurofibrillary tangle (NFT) scores. 3. To evaluate the safety of \[18F\]-APN-1607 injection.

Inclusion Criteria: 1. Able to understand and voluntarily sign a written informed consent form (ICF). 2. Age≥50 years, male or female. 3. Charlson Comorbidity Index (CCI)≥5. 4. Able to tolerate imaging procedures. 5. For MCI or AD subjects: clinically diagnosed as AD-derived cognitive impairment or Alzheimer's dementia. 6. For HV subjects: no known personal or family history of AD-derived dementia. Exclusion Criteria: 1. Confirmed brain structural abnormalities that may affect PET reading, e.g., large stroke (infarct area\>4 cm) or intracranial space-occupying lesion. 2. Currently having clinically significant infectious diseases: HIV, hepatitis, etc. 3. Currently participating in any investigational clinical trial. 4. Previous participation in clinical studies of amyloid or tau-targeting agents. 5. Suspected hepatic encephalopathy. 6. Allergy to the investigational drug or any of its components. 7. Currently pregnant or breastfeeding. 8. Currently having a disease or condition that prolongs the QT interval.