The cognition of aMCI is between normal aging and dementia, which is thought the transitional stage of dementia. Patients with aMCI have heavy risk to convert to AD, so in this study, the investigators focus on the construction of the diagnosis system for early AD based on multi-modality MRI characteristics of aMCI patients. Every patient underwent β-Amyloid PET, fluorodeoxyglucose-PET(FDG-PET), structural MRI, diffusion tensor imaging and functional MRI. Then investigators further study the patients who convert to AD and explore their MRI and metabolism characteristics on baseline, in order to construct the predictable classifier from aMCI to AD. The investigators want to achieve the early diagnosis of AD and help clinicians interfere with the progress of this disease.
