Use of 201Thallium brain SPECT, image registration, and semi-quantitative analysis in the follow-up of brain tumors.

OBJECTIVE

To assess the use of 201Thallium SPECT and of Thallium (Tl) uptake indices in the detection and follow-up of cerebral tumors.

MATERIAL AND METHODS

Two-hundred eighty 201Tl, 135 99mTc-HMPAO scintigraphies and 280 MRI studies were acquired in 135 patients with cerebral tumors. Three types of Tl uptake indices were calculated by establishing the ratio of the lesion activity to an homologous ROI (I1), the contralateral hemisphere (I2), and the contralateral scalp (I3). Intermodal coregistration between Tl-SPECT and MRI when used, was performed using Pietrzyk visual interactive method.

RESULTS

Tl uptake indices showed mean values of 2.0 +/- 0.5 (I1); 1.77 +/- 0.57 (I2) and 1.11 +/- 0.40 (I3) in positive scans, and of 1.05 +/- 0.22 (I1), 0.88 +/- 0.22 (I2) and 0.50 +/- 0.15 (I3) in negative scans, respectively. A linear combination of the two less correlated indices lead to a more powerful discrimination between positive and negative studies. Longitudinal follow-up studies in the same patients showed good concordance between the index values and the course of the disease.

CONCLUSION

The use of Tl uptake indices improves the accuracy of Tl-SPECT in the follow-up of brain tumors.