18F-FDG Accumulation with PET for Differentiation Between Benign and Malignant Lesions in the Thorax

Recent reports have indicated the value and limitations of 18 F-FDG PET and 201 Tl SPECT for determination of malignancy. We prospectively assessed and compared the usefulness of these scintigraphic examinations as well as 18 F-FDG PET delayed imaging for the evaluation of thoracic abnormalities. Methods: Eighty patients with thoracic nodular lesions seen on chest CT images were examined using early and delayed 18 F-FDG PET and 201 Tl-SPECT imaging within 1 wk of each study. The results of 18 F-FDG PET and 201 Tl SPECT were evaluated and compared with the histopathologic diagnosis. Results: Fifty of the lesions were histologically confirmed to be malignant, whereas 30 were benign. On 18 F-FDG PET, all malignant lesions showed higher standardized uptake value (SUV) levels at 3 than at 1 h, and benign lesions revealed the opposite results. Correlations were seen between 18 F-FDG PET imaging and the degree of cell differentiation in malignant tumors. No significant difference in accuracy was found between 18 F-FDG PET single-time-point imaging and 201 Tl SPECT for the differentiation of malignant and benign thoracic lesions. However, the retention index (Rl) of 18 F-FDG PET (Rl-SUVI significantly improved the accuracy of thoracic lesion diagnosis. Furthermore, 18 F-FDG PET delayed imaging measuring Rl-SUV metastasis was useful for diagnosing nodal involvement and it improved the specificity of mediastinal staging. Conclusion: No significant difference was found between 1 8 F-FDG PET single-time-point imaging and 201Tl SPECT for the differentiation of malignant and benign thoracic lesions. The Rl calculated by 18 F-FDG PET delayed imaging provided more accurate diagnoses of lung cancer.