This study is to evaluate the efficacy and safety of [18F]-APN-1607 Injection in PET imaging for detecting AD-related cognitive impairment.

Inclusion Criteria:

1. Subjects must be able to understand and voluntarily sign a written informed consent form (ICF);
2. Age ≥ 50 years, regardless of gender;
3. Subjects with HV, MCI, and AD should meet the clinical diagnostic criteria
4. Can tolerate brain MRI and PET imaging examinations;
5. For women of potential fertility (not yet menopausal or within 2 years of menopause), effective contraception must be used during the study and for 3 months after the study (effective contraception refers to sterilization, intrauterine hormonal devices, condoms, birth control pills, abstinence, or partner vasectomy, etc.); male participants should agree to use contraception during the study and for 3 months after the study.

Exclusion Criteria:

1. Specific clinical phenotypes of atypical AD as defined in the 2014 IWG-2 criteria
2. Possible presence of frontotemporal degeneration (FTLD), characterized by progressive psych behavioral abnormalities and executive dysfunction，Characterized primarily by impairment and language function, progressive aphasia
3. The core symptoms of Lewy body dementia include fluctuating cognitive changes accompanied by significant attention and arousal abnormalities, recurrent typical visual hallucinations, and spontaneous symptoms of Parkinson's syndrome;
4. Currently suffering from significant mental illness. Subjects with accompanying psychiatric symptoms need to be carefully evaluated by the researchers to determine whether they can complete the imaging process;
5. Brain structural abnormalities confirmed by MRI, such as large strokes (infarct area greater than 4 cm) or intracranial space-occupying lesions;
6. Suffering from claustrophobia or unable to tolerate imaging procedures for other reasons;
7. History of alcohol or drug abuse/dependency;
8. Hypersensitivity to the investigational drug or any of its components;
9. Currently pregnant or breastfeeding;
10. Received non-vaccine investigational treatment for Alzheimer's disease or other dementia within 3 months prior to screening, or received passive immunotherapy (antibody) for the treatment of Alzheimer's disease or other dementia within 6 months prior to screening, or previously received a vaccine for the treatment of Alzheimer's disease or other dementia; or participated in other new drug clinical trials within 30 days prior to enrollment;
11. At present, the researcher suffers from serious diseases, such as infectious diseases, infectious diseases, endocrine or metabolic diseases, as well as serious cardiac function, liver function, lung function, and kidney function damage, and believes that participation in this study will have adverse effects on the subject or the research results
12. Currently suffering from a disease or factor that causes QT interval prolongation, including torsades de pointes, QT prolongation syndrome, hyperkalemia, hypocalcemia, or taking medications that can prolong the QT interval, such as quinidine, amiodarone, or sotalol
13. There are other situations that researchers consider unsuitable for participating in the experiment.