Abstract: Differential Diagnosis of Mediastinal Lymph Node Metastasis in Lung Cancer Patients Using18F-FDG PET/CT with Double Quantitative SUVmax and CT ValueWenchao MA,Wengui XU, Xiang ZHU, Dong DAI, Xiuyu SONG, Lei ZHU, Yanjia ZHUCorrespondence to:Wengui XU, E-mail: wenguixy@tom.comKey Laboratory of Breast Cancer Prevention and Therapy, Tianjin Medical University, Ministry of Education; Key Laboratory of Can-cer Prevention and Therapy, TianjinThe Joint Laboratory of Molecular Imaging in Oncology, Tianjin Medical University Cancer Institute and Hospital and Institute of HighEnergy Physics of Chinese Academy of Sciences; Department of Molecular Imaging and Nuclear Medicine, Tianjin Medical UniversityCancer Institute and Hospital, Tianjin 300060, ChinaThis work was supported by the key project of Tianjin Natural Science Foundation (No.08JCZDJC23700), Research Project of TianjinEducation Commission (No.20080133), and Science Funds of Tianjin Municipal Bureau of Public Health (No.2010KZ80)Abstract Objective: To explore the quantitative differential diagnosis of lung cancer metastasis to mediastinal lymph nodes us-ing 18F-FDG PET/CT. Methods: The preoperative imaging outcomes of PET, CT and PET/CT of 142 patients with lung cancer ( LC )who underwent the examinations between April 2005 and October 2009 were retrospectively reviewed. The 142 LC patients receivedno anticancer therapy before undergoing 18F-FDG PET/CT scans. Surgery or puncture biopsy was performed one month after the exami-nations to obtain the pathological results. Mediastinal node staging was assessed in nine groups based on the N staging of lung cancerby the AJCC in 1997. Surgical and histological findings served as the reference standard. The images of PET, CT and PET/CT werequantitatively analyzed, the differences among SUVmax, the short axis and CT value of mediastinal lymph nodes were compared, andthe ROC curve was drawn according to the SUVmax and CT value of lymph nodes to find the best diagnostic differential point. Indicessuch as sensitivity, specificity, positive and negative predictive values, accuracy of simple PET and CT values, the short axis and PET/CT with double quantitative SUVmax and CT values were calculated. The diagnostic efficiency of these values and analyses was com-pared using the chi-square test. Results: There was statistical significance among SUVmax, the short axis and CT values of mediastinallymph nodes. A value of 2.45 was the best diagnostic differential point for SUVmax, and 38.5 was the best diagnostic differential pointfor CT scan. When SUVmax was ≥ 2.45, the CT value had statistical significance. However, the difference on the short axis did not