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

Twenty-five patients with malignant astrocytoma, either postoperatively (15 cases) or with recurrent tumour versus gliosis (10 cases) were included in this study. Tl-201 single photon emission computed tomography (SPECT) was performed with the calculation of early and delayed uptake values and retention index. A high mean value of early and delayed uptake correlated with a low retention index in patients with high-grade astrocytoma in both postoperative residual and recurrent groups, versus a lower mean value of early and delayed uptake with a high retention 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. There 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 sensitivity in detection of tumour viability by Tl-201 SPECT of 100% versus 80% using computed tomographic scanning and in the differentiation between recurrent tumour and postradiation gliosis.