Local cerebral blood flow measurements by xenon enhanced computer assisted tomography

Local cerebral blood flow (LCBF) was quantitated by a method of xenon enhanced computer assisted tomography (Xe-CT) and its methodological problems were assessed. The materials consisted of 7 healthy controls and 9 patients with cerebral infarctions. The optimal concentration of xenon gas was found to be approximately 50% derived from data on xenon enhanced rate, signal to noise ratio and known anesthetic effects of xenon gas. A method of inhalation technique of short duration was designed for making it less traumatic. Scan interval was set every 1 minute in early phase of inhalation following by every 5 minutes thereafter. The scan data were treated by exponential curve fittings as modified from the autoradiography method. The results disclosed that measurements of LCBF in basal ganglia and thalamus were reasonably accurate by 6 minutes inhalation. By this method a mean value of LCBF of basal ganglia in healthy controls was 85.7 + 19.3 ml/100g/min correlating well to a mean value of 94.8 + 17.4 ml/100g/min as derived from actual saturation curves. The calculation of LCBF was considered most reliable from the aspects of effciency of scanner and of radiation dose when xenon built-up curves were selected for calculations of in vivo autoradiography. (author)