USE OF (201)THALLIUM BRAIN SPECT, IMAGE REGISTRATION, AND SEMIQUANTITATIVE ANALYSIS IN THE FOLLOW-UP OF BRAIN-TUMORS

Objective: To assess the use of (201)Thallium SPECT and of Thallium (T 1) uptake indices in the detection and follow-up of cerebral tumors. M aterial and methods: Two-hundred eighty (201)T1, 135 Tc-99m-HMPAO scin tigraphies and 280 MRI studies were acquired in 135 patients with cere bral tumors. Three types of T1 uptake indices were calculated by estab lishing the ratio of the lesion activity to an homologous ROI (I-1), t he contralateral hemisphere (I-2), and the contralateral scalp (I-3) I ntermodal coregistration between TI-SPECT and MRI when used, was perfo rmed using Pietrzyk visual interactive method. Results: T1 uptake indi ces showed mean values of 2.0 +/- 0.5 (I-1); 1.77 +/- 0.57 (I-2) and 1 .11 +/- 0.40 (I-3) ill positive scans, and of 1.05 +/- 0.22 (I-1), 0.8 8 +/- 0.22 (I-2) and 0.50 +/- 0.15 (I-3) in negative scans, respective ly. A linear combination of the two less correlated indices lead to a more powerful discrimination between positive and negative studies. Lo ngitudinal follow-up studies in the same patients showed good concorda nce between the index values and the course of the disease. Conclusion : The use of T1 uptake indices improves the accuracy of TI-SPECT in th e follow-up of brain tumors.