Early dynamic 201Tl SPECT in the evaluation of brain tumours

OBJECTIVETo estimate the usefulness of early dynamic Tl single photon emission computed tomography (SPECT) studies in distinguishing the histological malignancy of brain tumours. METHODSDynamic Tl SPECT was performed for 3 min per scan for 15 min immediately after the administration of TlCl in 110 patients with brain tumours (111 lesions). The data obtained each 3 min were used for dynamic SPECT, and the five sets of data obtained were added to acquire static SPECT data. For static SPECT, the static thallium index (STI) was calculated as the ratio of Tl uptake in the tumour to that of the contralateral normal brain. The ratio of the Tl uptake for each 3 min was defined as the dynamic thallium index (DTI). The dynamic thallium rate (DTR), as a per cent, was calculated as DTR=(DTI for every 3 min)/STI H 100. The five values were approximated as a linear function and the slope (%/min) was calculated. RESULTSIn static SPECT, there was no significant difference between the STI of malignant tumours (glioblastoma and anaplastic astrocytoma) and that of benign tumours (low-grade glioma, meningioma, pituitary adenoma, neurinoma and haemangioblastoma) (3.7±1.5, 5.0±3.5, respectively). On dynamic SPECT, DTI increased markedly over 15 min for malignant tumours. In contrast, the DTI of benign tumours increased slightly, steadily or decreased. The slope of the linear functions calculated from the DTRs was much higher in the malignant tumour group than in the benign tumour group (P