Thallium-201 SPECT with triple-headed gamma camera for differential diagnosis of small pulmonary nodular lesion 20 mm in diameter or smaller

[Aim] Although thallium-201 ((TI)-T-201) has been used for the diagnosis of lung cancer, its detectability of small pulmonary nodules is not known. Th e aim of this study was to evaluate the ability of Tl-201 SPECT for the dif ferential diagnosis for the pulmonary nodules 20 mm in diameter or smaller. [Methods] (TI)-T-201 SPECT was performed in 31 patients suspected of havin g primary lung cancer. The final diagnosis was established by histology, an d tumor size was 10 to 20 mm in diameter. Twenty of 31 patients had maligna nt tumors, including squamous cell lung cancer (n = 5), adenocarcinoma (n = 14) and small cell lung cancer (n = 1), but in none of them was there medi astinal lymphnode involvement. [Results] Ten bf 20 malignant tumors and 1 o f 11 benign lesions demonstrated significant Tl-201 uptake, so that the pos itive predictive value, negative predictive value, sensitivity and specific ity for the diagnosis of lung cancer were 90.9% (10/11), 50.0% (10/20), 50. 0% (10/20) and 90.9% (10/1 i), respectively. [Conclusion] These data sugges t that sensitivity for detecting lung cancer 20 mm or less in diameter may be insufficient, but even in patients with small pulmonary nodules, a posit ive Tl-201 result is highly predictive of lung cancer.