Using SV2A-PET to character a cohort of patients with early cognitive impairment using the novel synaptic probe 18F-labeled difluoro-analog of UCB-J（also known as 18F-SDM-8）

A community-based population (Han Chinese) in Hefei, China, based on the CANDI cohort；Single-center prospective case-control study；The projected enrollment population is 80; 40 patients with Alzheimer's Disease（AD）, 30 patients with Mild Cognitive Impairment（MCI）; 10 healthy controls. Diagnostic experiments and predictive prognostic experiments with new probes.

Inclusion Criteria:

• AD Group
• All diagnostic criteria for AD patients met the National Institute of Neurological Speech-Language Disorders Stroke Institute and Alzheimer's Disease and Related Disorders Association criteria;
• Comply with the American Psychiatric Association Diagnostic and Statistical Workbook of Mental Disorders, 5th edition (DSMIV);
• All subjects were unconscious and could be accompanied by behavioral and psychiatric abnormalities. Subjects who meet the above criteria are eligible for enrollment.
• Those who understand the process of this clinical trial and sign the informed consent form (in addition, non-AD volunteers will be recruited through verbal dissemination and posting of paper advertisements to serve as the non-AD control group, and the final control group will be screened by the clinician and consist of healthy people of similar age and gender).
• MCI Group
• Concerns about cognitive changes, and concerns about finding changes in comparison with one's prior level may originate from the patient himself or herself, from an informed person, or from an experienced specialist;
• Impairment of one or more cognitive areas, primarily memory, executive function, attention, language, and visuospatial function;
• Maintaining independence in daily living, there can be minor impairment in complex instrumental daily abilities;
• Absence of dementia, mild disease, and no evidence of serious impairment of social or occupational abilities;
• Presence of one of the Aβ class biomarkers and/ neuronal damage class markers detected by imaging, cerebrospinal fluid;
• All subjects and their guardians give informed consent to the study and sign the informed consent form;

Exclusion Criteria:

• With confirmed cerebrovascular disease, the presence of multiple or extensive cerebral infarcts;
• Other types of dementia: Parkinson's disease dementia, vascular dementia, frontotemporal lobe dementia, dementia with Lewy bodies;
• Sudden onset or stroke-like episodes;
• Early onset of focal neurological symptoms, such as hemiparesis, computational deficits, ataxia, or sensory loss;
• Seizures or gait abnormalities early in the onset of the disease;
• Evidence of drug applications that cause significant effects on cognitive function;
• Those who are allergic to alcohol;
• Persons with alcohol allergy; (ix) Persons with left-handedness; (x) Persons with left-handedness;
• Those with claustrophobia or other reasons for not being able to cooperate with the examination;
• Those with serious heart, liver, lung, kidney and other organ diseases, meeting the above conditions were excluded from the group.

This study is a single-center prospective exploratory clinical trial, and given this, it is proposed to initially enroll only 80 evaluable subjects (including 40 patients with ALZHEIMER'S DISEASE, 30 patients with MILD COGNITIVE DISABILITY, and 10 age-sex matched non-ALZHEIMER 'S DISEASE controls), each subject underwent 18F-SDM-8 PET/CT imaging, the ability of the tracer to bind to SV2A in the brain as well as non-specific binding, and correlation analysis with changes in relevant clinical indicators to assess the safety and diagnostic efficacy of the tracer.