[Isocount scanning in brain tumors-a quantitative investigation of the tracer activity (author's transl)].

In the previous reports, the theoretical background [corrected] and technical details of the Isocount scanning were described. Based on clinical experiences of various brain diseases, the newly developed scanning method was confirmed to be more useful than the conventional scintiscanning. Besides the new scanning method, a new display system was also developed for the sake of more precise analysis of the Isocount scanned data. This display method is called MULTILEVEL ANALYSIS or MULTILEVEL SLICING. In the present investigation, this method was applied to fortysix cases of brain tumors, including forty cases of supratentorial tumors and six cases of infratentorial tumors, positive rates being 95% and 67% respectively. Furthermore, as a measure of the quantitative investigation of the radioactive tracer uptake of the target area, the maximum uptake rate of the target area (RTmax.=Tmax./NTmean), and the deviation index (DI=DT/DNT) were introduced; Tmax., NTmean, DT and DNT are respectively defined as a maximum uptake of the target area, a mean uptake of the non-target area, a deviation rate of the target area and a deviation rate of the non-target area. They can be obtained from analysing the television figures of MULTILEVEL ANALYSIS. By this method, thirty-four cases of supratentorial tumors were studied. In cases of glioma (12 scans), meningioma (9 scans), and metastatic tumor (7 scans), the mean values of RTmax. were 1.26, 1.37, and 1.24 and the mean values of DI were 0.81, 0.68 and 0.60 respectively. In gliomas, the RTmax. and the DI were correlated with the degree of malignancy of the tumors. This quantitative analysis could be considered to be useful to foresee the nature of the brain tumor from the scintiscanning findings.