Abstract: Objective: To evaluate the clinical value of PET-CT in judging mediastinal lymph nodes metastasis of lung cancer. Methods: A retrospective review of the CT, PET and PETCT findings of 67 patients was performed. In operations, 319 mediastinal lymph nodes samples were acquired by resection, and 68 metastasis lymph nodes were proved by pathology. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of CT, PET and PET-CT were determined. Results: In detecting mediastinal lymph node metastasis, the accuracy of CT, PET and PETCT scans was 74.6%, 80.9% and 88.7%； the sensitivity of them was 61.8%, 80.9% and 86.8%；the specificity was 78.1%, 79.4% and 89.2%； the PPV was 43.3%, 53.4% and 68.6%； the NPV was 88.3%, 93.4% and 96.1%. The accuracy of PET-CT scans was significantly better than that of PET or CT scans in determining mediastinal lymph node metastasis(P＜0.01). Conclusion: PET-CT is more accurate than PET or CT.

Key words: Positron emission tomography, X ray computed, Lung neoplasms, Lymph nodes, metastasis