Clinical application of 201Tl SPECT imaging of brain tumors

This study investigated the clinical usefulness of evaluating the histologic grade of brain tumors by Tl-201 SPECT brain imaging. Methods: Early and delayed SPECT brain images were obtained about 10 min and 3 h, respectively, after intravenous injection of 111MBq (3 mCi) Tl-201 in 9 healthy subjects (control subjects), 3 patients with brain hematomas, and 41 patients with brain tumors. Semiquantitative data were obtained for early and delayed Tl-201 uptake indices and Tl-201 retained index in all patients and healthy subjects. Results: In 9 healthy subjects, there was little radioactivity in brain substance. In all patients with brain hematomas or tumors, a high tracer uptake was visible in lesions on early images, but the radioactivity in lesions varied with the histologic nature of the lesion on delayed images. The radioactivity decreased remarkably in brain hematomas (average retained index, 0.61 +/- 0.04). The radioactivity was stable or decreased slightly in benign or low-grade tumors (average retained index, 0.96 +/- 0.24). The radioactivity was increased in high-grade or metastatic tumors (average retained index, 1.26 +/- 0.28). Conclusion: This study indicates that Tl-201 brain SPECT early and delayed imaging is very useful in brain tumor localization, in distinguishing low-grade from high-grade brain tumors, in predicting histologic grades of brain tumors, and in detecting residual or recurrence of brain tumors postoperatively. Tl-201 brain SPECT may also offer the most accurate assessment of response to therapy.