BACKGROUND AND OBJECTIVE. There is a need for objective semiquantitative indexes for the evaluation of results of single-photon emission tomography (SPECT) in patients with brain glioma. The aim of this study was to validate the total size index (TSI) and total intensity index (TII) based on technetium-99m-methoxyisobutylisonitrile ((99m)Tc-MIBI) SPECT scans to discriminate the patients with high-grade glioma versus low-grade glioma and to evaluate the changes of viable glioma tissue by the means of TSI and TII after surgery and after radiation treatment. MATERIAL AND METHODS. Thirty-two patients (mean age, 55 years [SD, 18]; 20 men) underwent a (99m)Tc-MIBI-SPECT scan before surgery. Of these patients, 27 underwent a postoperative (99m)Tc-MIBI-SPECT scan and 7 patients with grade IV glioma underwent a third (99m)Tc-MIBI-SPECT scan after radiation treatment. TII that corresponds to the area and intensity of tracer uptake and TSI that corresponds to the area of tracer uptake were calculated before surgery, after surgery, and after radiation treatment. RESULTS. The TII and TSI were found to be valid in discriminating the patients with high-grade versus low-grade glioma with optimal cutoff values of 3.0 and 2.5, respectively. Glioma grade correlated with the preoperative TSI score (r=0.76, P<0.001) and preoperative TII score (r=0.64, P<0.001). There was a significant decrease in the TII and TSI after surgery in patients with grade IV glioma. After radiation treatment, there was a significant increase in the TII in patients with grade IV glioma. CONCLUSIONS. TSI and TII were found to be reliable in discriminating the patients with high-grade versus low-grade glioma and allowed for the semiquantitative evaluation of change in viable glioma tissue after surgery and after radiation treatment in patients with grade IV glioma.