Comparison of two-phase (201)Tl SPECT with chest CT to differentiate thoracic malignancies from benign lesions

This study was conducted to compare the performance of (201)Tl single photon emission computed tomography ((201)Tl SPECT) with chest computed tomography (CT) in differentiating thoracic malignancies from benign lesions.

One hundred and seventy patients with confirmed diagnostic thoracic lesions found in chest radiographs were prospectively examined by (201)Tl SPECT. The performance of (201)Tl SPECT in differentiating thoracic malignancies from benign lesions was evaluated in 161 patients with a measurable retention index (RI), using the region-of-interest method. Chest CT scans were retrospectively collected from 165 patients and were interpreted by two independent observers.

The areas under the receiver operating characteristics curves were 0.85 using the RI value to differentiate thoracic malignancies from benign lesions. The sensitivity, specificity, and accuracy were 71.9%, 83.1%, and 76.4%, respectively, with a cutoff level for the RI set at 20%. Similarly, the sensitivity, specificity and accuracy of chest CT scans to differentiate malignancies from benign lesions were 78.2%, 69.7% and 74.9%, respectively. Focusing on patients with concordant results in both (201)Tl SPECT and chest CT scans, we can differentiate thoracic malignancies from benign lesions with a sensitivity of 89.1%, a specificity of 90%, and an accuracy of 89.4%.

Both (201)Tl SPECT and chest CT scans are useful imaging tools in differentiating thoracic malignancies from benign lesions, with an accuracy of around 75%. By combining these two image modalities, the accuracy improves to 89.4%, which may circumvent the need for invasive procedures for certain equivocal cases, using either single image alone.