Detection of lung lesions and lymph nodes with 201Tl SPET

The aim of this study was to characterize lung lesions by means of the uptake, retention and washout of Tl-201, and to quantify the sensitivity of Tl-201 SPET (single photon emission tomography) in detecting mediastinal and hilar lymph nodes. A total of 68 patients with lung lesions (tumours and inflammation) underwent both helical computed tomography (CT) and Tl-201 SPET examinations. Uptake, retention and washout parameters were calculated from early and delayed Tl-201 SPET by drawing regions of interest over the primary lesion and the background of the lung. The findings on Tl-201 SPET were compared with those on CT and surgical findings. A significant difference in the retention index (RI) was observed between primary malignant and benign lesions. In detecting lymph nodes, the sensitivity, specificity and negative predictive value were 83%, 60% and 90% respectively for early Tl-201 SPET, and 50%, 80% and 80% respectively for delayed Tl-201 SPET. Tl-201 SPET with semi-quantitative analysis, especially RI, helps to differentiate between malignant and benign lung lesions. Lymph nodes larger than 1 cm on CT but not showing Tl-201 uptake could be considered non-metastatic lesions. ((C) 1998 Lippincott-Raven Publishers).