Usefulness of Thallium-201 Single Photon Emission Computed Tomography to Quantify the Malignancy Grade of Brain Tumors

Abstract

Preoperative thallium-201 (²⁰¹Tl) single photon emission computed tomography (SPECT) was used to evaluate the histological malignancy in 24 patients with brain tumors. A corrected L/E ratio was calculated based on the ratio of thallium uptake in the tumor on early images versus the tumor in the delayed images (L/E ratio) corrected for thallium uptake in the contralateral cerebral hemisphere. The corrected L/E ratio in benign brain tumors was 0.79 ± 0.23, significantly different to 1.32 ± 0.25 in high grade astrocytomas (p < 0.01) and 1.19 ± 0.05 in metastatic brain tumors (p < 0.01), respectively. The corrected L/E ratio in low grade astrocytomas was 0.64 ± 0.32, significantly lower than that in high grade astrocytomas (p < 0.01) and metastatic brain tumors (p < 0.05). There was one false positive result among 24 patients using a threshold of 1.0 to separate malignant and benign tumors. ²⁰¹Tl SPECT using the corrected L/E ratio is effective for determining the malignant viability of tumors.