[Estimation of malignancy using SPECT with 201Tl chloride in astrocytic tumors]

This study was designated to estimate the usefulness of SPECT with 201Tl chloride (Tl-SPECT) for the determination of the malignancy in astrocytic tumors. The subjects consisted of 39 astrocytic tumors in supra-tentorial regions. Tl-SPECT undertaken ten minutes to obtain an early image and four hours to obtain a delayed image, after intravenous injection of 74MBq 201Tl chloride (Tl). Tl index (L/N) was defined as the RI count ratio in the tumor lesion (L) to that in the normal parenchyma (N). Histological classification was determined by the WHO grading, and the results showed one case at Grade I, 11 cases at Grade II, 23 cases at Grade III and 4 cases at Grade IV. The proliferating activity was determined by the labeling index using the monoclonal antibody of proliferating cell nuclear antigen (PCNA). In both of the early and delayed images, Tl index was significantly higher (p < 0.01) in high grade astrocytomas compared with low grade tumors. There was a close correlation between the Tl index and the proliferating activity. The relationship between the Tl index and prognosis indicated that the high Tl index was corresponded to the poor prognosis. These results showed that the Tl index is useful to determine the malignancy of astrocytic tumors.