Tl-201 SPET in the differential diagnosis of brain tumours

The aims of this study were to assess the utility of Tl-201 Single photon e mission tomography (SPET) in the differential diagnosis of brain tumours an d to elucidate the relationship between Tl-201 tumour uptake and degree of contrast-enhancement on magnetic resonance imaging (MRI). Early (15 min) an d delayed (3 h) Tl-201 SPET imaging and T-1-weighted MRI were performed bef ore and after Gd-DTPA enhancement in 101 (41 malignant and 60 benign) untre ated brain tumours. The Tl-201 uptake ratio (tumour-to-normal brain count r atio) for both the early and delayed SPET studies and the retention index ( the ratio of delayed to early Tl-201 uptake) were calculated. Malignant tum ours were separated from benign tumours with 87% accuracy based on the assu mption that tumours with a Tl-201 retention index <0.7 or no abnormal uptak e are benign. Meningiomas and pituitary adenomas were differentiated from o ther benign tumours by their characteristic pattern on SPET. The degree of contrast-enhancement of the tumour on MRI was concordant with the early Tl- 201 uptake ratio for most histological types. However, schwannomas and cave rnous haemangiomas showed a low Tl-201 uptake ratio in spite of a high degr ee of contrast-enhancement on MRI. In conclusion, Tl-201 SPET provides addi tional information that helps in the differential diagnosis of brain tumour s. ((C) 1999 Lippincott Williams & Wilkins).