Abstract: Brain perfusion SPECT is a functional and noninvasive neuroimaging technique that allow the investigation of physiological and physiopathological events in the human brain,including cerebral perfusion and function.Interventional rCBF imaging can also evaluate cerebrovascular reserve.In clinically,rCBF imaging play an important role in the diagnosis and differential diagnosis of dementias,especially vascular and Alzheimer's dementia.If etiology of some types of dementias is determined so that it can be early diagnosed,treated and taken prevention;the partial patients with dementia can get recovery or remission.