Inclusion Criteria:

1. Between 18 and 90 years old;
2. No gender limitation;
3. Clinical diagnositic rerults supported the diagnosis of neurodegeneration, and there was no evidence of other neurological diseases;
4. Healthy participants or patients with probable Alzheimer's disease or with dementia due to other causes;
5. Informed consent signed in person by the subject or his legal guardian or caregiver.

Exclusion Criteria:

1. Has allergy to [18F]NIDF or any of its excipients;
2. Incapable of providing written informed consent or lacking a legally authorized representative (LAR) to provide informed consent ;
3. Unwilling or unable to undergo PET scans tracer injections;
4. Any condition that, in the Investigator's opinion, could increase the risk to the participant, limit the participant's ability to tolerate the research procedures, or interfere with the collection/analysis of the data (e.g., renal or liver failure, advanced cancer);
5. Received an experimental drug or device within 1 month (whose efficacy or safety is unclear);
6. Have other serious neurological disorders, or gastrointestinal, cardiovascular, liver, kidney, blood system, tumor, endocrine, respiratory, immune deficiency, and other serious diseases;
7. Women who are currently pregnant or breastfeeding.