SPECT imaging in psychiatry: introduction and overview.

Positron emission tomography (PET) and single photon emission computed tomography (SPECT) use advanced computer image construction techniques to illustrate regional cerebral function, metabolism, and chemistry. Although the resolution of PET is higher than that of SPECT, and the technical development of SPECT has lagged behind that of PET, SPECT has recently enjoyed increasingly widespread use, particularly because its costs and technology are within the reach of all clinical nuclear medicine facilities. SPECT imaging agents have greater half-lives than those used with PET, thereby permitting longer and more detailed neurochemistry study than is possible with PET. The research value of both methods has unique potential compared with computed tomography (CT) and magnetic resonance imaging (MRI), which traditionally have provided a static image of the brain's structure or anatomy.