Assessment of glioma viability by estimating Tl-201 SPET tumour uptake volume

The aim of this study was to develop a quantitative method to assess viable tumour based on postoperative Tl-201 Single photon emission tomography (SP ET). We studied 15 patients with histologically defined highly malignant gl iomas in the post-operative phase before initiation of adjuvant treatment. A Tl-201 index was calculated in two ways: maximal counts versus mean count s within a region of interest (ROI). The tumour uptake volume (TUV) within the lesion was calculated from the number of voxels that had Tl-201 uptake above a threshold calculated from the uptake on the contralateral side. The threshold was set at three levels: A = 1.4 times the mean Tl-201 uptake in a three-dimensional reference ROI + 96.7% confidence interval (the TUV was corrected by subtraction of the volume in the reference ROI that had uptak e above the threshold with compensation for unequal ROI sizes); B=1.4 times the mean reference ROI + 99% confidence interval; and C = maximum Tl-201 u ptake in the reference ROI. The SPET results were compared with the tumour volumes calculated from CT scans. Thirteen rumours showed high post-operati ve Tl-201 uptake. The Tl-201 index was not significantly correlated with hi stological grade within the group of highly malignant gliomas. Tl-201 SPET tumour uptake volume method B was highly significantly correlated with CT e stimated tumour volume. In conclusion, the measurement of postoperative Tl- 201 SPET tumour uptake volume demonstrates metabolically active glioma tiss ue and is an alternative method for the monitoring of glioma treatment resp onse. ((C) 1999 Lippincott Williams & Wilkins).