[en] The authors followed up the change in SPECT using ²⁰¹Tl chloride (Tl-SPECT) according to the course of treatment of intracranial gliomas and analyzed the difference in Tl-SPECT between the stable and progressive groups. The subjects were 26 series of supratentorial gliomas subjected to Tl-SPECT before and after the treatment (radiotherapy and chemotherapy). They were put on Tl-SPECT after 10 minutes (early image) and 4 hours (delayed) following intravenous injection of 74 MBq of ²⁰¹Tl. Besides, RI count ratio (L/N) in the tumor lesion (L) to the contralateral parenchyma (N) was measured. The patients were divided into stable and progressive groups judging from the therapeutic efficacy. The change in L/N ratio before and after the treatment was analysed. The stable group showed a significant post-treatment decrease in L/N ratio compared with a significant post-treatment increase for the progressive group. This suggested that Tl-SPECT would change according to the course of treatment and aid in the therapeutic judgement in gliomas. (author)