Detection of lung lesions and lymph nodes with ²⁰¹t1 spet

The aim of this study was to characterize lung lesions by means of the uptake, retention and washout of ²⁰¹Tl, and to quantify the sensitivity of ²⁰¹Tl 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 ²⁰¹Tl SPET examinations. Uptake, retention and washout parameters were calculated from early and delayed ²⁰¹Tl SPET by drawing regions of interest over the primary lesion and the background of the lung. The findings on ²⁰¹Tl 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 ²⁰¹Tl SPET, and 50%, 80% and 80% respectively for delayed ²⁰¹Tl SPET. ²⁰¹Tl 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 ²⁰¹Tl uptake could be considered non-metastatic lesions.