The use of dual phase ²⁰¹Tl SPECT for differentiating pulmonary malignancies from benign lesions

Background: This study examines the usefulness of thallium-201 single photon emission computed tomography (²⁰¹Tl SPECT) in differentiating pulmonary malignancies from benign lesions by using dual phase ²⁰¹Tl scintigraphy. Methods: One hundred and six patients with thoracic lesions and confirmed diagnoses were assessed by ²⁰¹Tl chest SPECT examinations; of these 106 enrolled thoracic lesions, 59 were malignancies and 47 were benign lesions. Dual phase ²⁰¹Tl SPECT was performed with an early image acquired at 10-20 min and a delayed image at 2-3 h after intravenous injection of 2-3 mCi of ²⁰¹Tl. The results of ²⁰¹Tl SPECT images were classified as either malignant or benign lesions by visual interpretation: the lesion was interpreted as positive for malignancy if the uptake of ²⁰¹Tl in the lung lesion in the delayed phase was increased or persistent as compared with that in the early phase image; otherwise, it was considered as a benign lesion. Simultaneously, the traditional method of retention index (RI) was also calculated to help in the differential diagnosis of pulmonary lesions. Then, both methods of dual phase ²⁰¹Tl SPECT, visual reading and traditional RI, were compared to differentiate pulmonary malignancies from benign lesions. Results: Analyzing the image results, we found that dual phase ²⁰¹Tl SPECT could differentiate pulmonary malignancies from benign lesions with a sensitivity of 83%, a specificity of 91% and an accuracy of 87%. Moreover, by using the traditional RI method of ²⁰¹Tl SPECT, it could differentiate pulmonary malignancy from benign lesions with a sensitivity of 79.3%, a specificity of 80.8% and an accuracy of 80%. Conclusions: We conclude that using dual phase ²⁰¹Tl SPECT with visual interpretation is a simpler and potentially more effective method for differentiating pulmonary malignancies from benign lesions, with results compatible with the traditional RI method of ²⁰¹ Tl SPECT.