[The contribution of single-photon emission-computed tomography in cerebral function diagnosis]

Single photon emission computed tomography (SPECT) makes it possible to visualize physiological and chemical processes in the cerebrum. In this technique, single photon emitting nuclides such as 99m technetium and 123 iodine, which are tagged to other compounds, or 133xenon, are used for the study of several clinical conditions. After injection of the radiopharmaceutic agent the radioactivity is measured by a rotating gamma-camera from numerous directions. Based on the measured values, its distribution within the brain can be computed and transformed in tomographic slices. We present our experience with the method in clinical practice using preferentially N-isopropyl-(123I)-p-iodoamphetamine (123I-IMP) and 99mTc hydroxymethyl-propylene-amine-oxime (99mTc-HMPAO). These substances are distributed in accordance with regional cerebral blood flow (rCBF). Hitherto, the application of the method has concentrated on the study of cerebrovascular disease and epilepsy. SPECT has contributed to a better understanding of the pathophysiological processes and their dynamics after ischemic infarction. The method also provides essential insights in epileptics. In partial epilepsy, a focus of reduced or enhanced tracer activity can be ascertained, dependent on the timing of the examination, in the interictal and ictal stage respectively. Even in the early course of senile dementia of Alzheimer type, zones of diminished neuronal activity in temporo-parietal and frontal cortex are demarcated. Preliminary results in psychiatric diseases and parkinsonism need further confirmation. In this connection future interest will focus especially upon the use of receptor ligands.