TL-201 SINGLE-PHOTON EMISSION TOMOGRAPHY IN THE EVALUATION OF RESIDUAL AND RECURRENT ASTROCYTOMA

Twenty-five patients with malignant astrocytoma, either postoperativel y (15 cases) or with recurrent tumour versus gliosis (10 cases) were i ncluded in this study. Tl-201 single photon emission computed tomograp hy (SPECT) was performed with the calculation of early and delayed upt ake values and retention index. A high mean value of early and delayed uptake correlated with a low retention index in patients with high-gr ade astrocytoma in both postoperative residual and recurrent groups, v ersus a lower mean value of early and delayed uptake with a high reten tion index in patients with low-grade tumours. All postoperative cases with high-grade astrocytoma had high Tl-201 uptake >1.5, whereas 66.6 % of cases with low-grade astrocytoma had low Tl-201 uptake <1.5. Ther e was a correlation between retention index of Tl-201 and tumour grade with r = 0.47. Also, recurrent cases showed remarkable differences in early and delayed Tl-201 uptake (P < 0.05) and retention index (P < 0 .001) compared with postradiation gliosis. There was a higher sensitiv ity in detection of tumour viability by Tl-201 SPECT of 100% versus 80 % using computed tomographic scanning and in the differentiation betwe en recurrent tumour and postradiation gliosis.