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 (RI) of (18)F-FDG PET (RI-SUV) significantly improved the accuracy of thoracic lesion diagnosis. Furthermore, (18)F-FDG PET delayed imaging measuring RI-SUV metastasis was useful for diagnosing nodal involvement and it improved the specificity of mediastinal staging. CONCLUSION: No significant difference was found between (18)F-FDG PET single-time-point imaging and (201)Tl SPECT for the differentiation of malignant and benign thoracic lesions. The RI calculated by (18)F-FDG PET delayed imaging provided more accurate diagnoses of lung cancer.