To investigate the primary brain regions of precursors of Alzheimer's disease and Alzheimer's disease by novel molecular probe [18F]AV45(Aβ) and [18F]AV1451(Tau)PET/CT imaging. And the distribution of positive lesions in the brain area affecting the simple mental state examination and the Montreal Cognitive Assessment Scale in AD patients; It is expected to provide molecular imaging information for further study of the pathogenesis of AD. After clinical transformation, objective and quantitative positive diagnostic criteria for [18F]AV45 and [18F]AV1451PET/CT in the diagnosis of early Alzheimer's disease were established to avoid the defects of relying on the subjective experience of doctors and time-consuming diagnosis.

Inclusion Criteria:

• Meet the MCI diagnostic criteria of Peterson in 2004;
• The clinicaldementiarating Scale (CDR) score was 0.5;
• Prominent memory loss may also be accompanied by impairment of other cognitive domains;
• Insidious onset and slow progression;
• Not at the level of dementia.

AD entry criteria:

• Meet the criteria for diagnosing dementia as described in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-R), Use the diagnostic criteria for AD from the National Institute of Neurology, Speech and Communication Disorders and Stroke - Alzheimer's Disease and Related Disorders (NINCDS-ADRDA) or the National Institute on Aging and Alzheimer's Disease Association (NIA-AA).
• Clinical Dementia Rating Scale score was 1 point.

Exclusion Criteria:

• Patients with a history of stroke and focal neurological signs, and imaging findings consistent with small cerebral vascular disease (Fazekas score ≥2);
• The presence of other neurological disorders that can cause brain dysfunction (e.g., depression, brain tumors, Parkinson's disease, metabolic encephalopathy, encephalitis, multiple sclerosis, epilepsy, brain trauma, Normal facial pressure hydrocephalus);
• The presence of other systemic diseases that can cause cognitive impairment (such as liver insufficiency, renal insufficiency, thyroid dysfunction, severe anemia, folic acid or vitamin B12 deficiency, syphilis, HIV infection, alcohol and drug abuse, etc.);
• There is mental and neurological retardation.
• There are other diseases that are known to cause cognitive impairment.

It is expected to include 100 patients with MCI, 100 patients with AD, and 80 patients in the NC group, A total of 280 patients, all of whom received Aβ and TauPET/CT imaging. There were 180 males and 100 females.