PET: a biological imaging technique.

Like in vivo autoradiography, PET provides a means to image and measure rates of biological processes throughout the distributed and interrelated systems of the entire living brain. In addition, both techniques can track and image the functional interactions of the brain with other systems throughout the entire body. Technological advances are yielding higher image spatial resolution and "Electronic generators" for automated synthesis of positron labeled compounds. The expanding number of labeled compounds (greater than 500) is providing a growing number of biological assays (i.e., substrate metabolism, pre and post synaptic processes, enzyme activity, interaction of medical and illicit drugs with biological systems of the brain, immune system, membrane processes). Studies of normal cerebral function focus on mapping evoked responses of various components of motor, visual, somatosensory, memory and cognitive functions. Cerebral development, neuronal plasticity, and compensatory reorganization to lesions or surgery are active areas of investigation. Various types of assays have been used to identify specific biological alterations, map progression and determine therapeutic responses in a wide variety of neuropsychiatric disorders and drug abuse.