[3-dimensional scintigraphy of the brain: single photon emission computerized tomography]

Both IMP and HMPAO are lipophilic substances with high blood brain barrier permeability and sufficiently long constant retention in the brain parenchyma to enable SPECT to be carried out with a computer controlled Gamma camera. Both tracers are almost completely cleared from the blood during a single passage through the brain. Hence, the regional distribution of activity in the brain is proportional to the regional cerebral blood flow. Computerized acquisition and data processing result in 16 mm thick tomograms at a spatial resolution of 12 mm, which enable clinicians to detect and characterize the pathogenesis and the development of cerebral disorders in terms of altered function. At present, SPECT can be used in daily clinical routine (final SPECT images are available 30 min after the investigation) in cerebrovascular diseases and, because of the coupling of metabolism to cerebral blood flow, in disturbances of cerebral blood flow due to pathological changes of brain metabolism, i.e. in epilepsy and in degenerative disorders. The forthcoming application of physiologically highly specific tracers (e.g. receptor ligands) as a means of studying the distribution of receptors and drugs in the brain will further enlarge the eventual role of SPECT in clinical management.