Evaluation Of Lung Cancer Histologic Classification And Lymph Nodes Metastases:Initial Experience With Spectral CT Imaging

Section I Evaluation of histologic classification of lung cancer: initial experience with spectral CT imagingObjective:To detect the usefulness of gemstone spectral CT in histologic classification of lung cancer.Methods:71patients with primary lung cancer confirmed by histopathology were retrospectively analyzed. They all got contrast-enhanced gemstone spectral imaging scanning before therapy. Among the71cases of lung cancer,27cases were squamous cell carcinoma,34cases were adenocarcinoma, and the other10cases were small cell lung cancer. The iodine concentrations (IC) on the iodine-based material-decomposition images, the CT values at different mono kilo electron volt (keV) and the spectral attenuation curve were measured in the lesions respectively. The slopes of the curve and the normalized iodine concentration (NIC) value against the aorta were calculated. Data among different histological types of lung cancer were analyzed comparatively by analysis of variance. The ROC curve of these spectral parameters were calculated and the diagnostic value were assessed.Results:There were no significant differences between the squamous cell carcinoma and adenocarcinoma in the CT values, the slopes, IC value and NIC value (P=1.000). The NIC showed significant differences between small cell lung cancer (SCLC) and squamous cell carcinoma (0.25±0.10&0.34±0.10, P=0.034) or adenocarcinoma (0.25±0.10&0.32±0.11,P=0.045). The best cut-off point of NIC in diagnosing SCLC was0.2508. The sensitivity, specificity, positive predictive value and negative predictive value and accuracy was86%,70%.95%,50%and78%respectively.Conclusion:Squamous cell carcinoma and adenocarcinoma can not be differentiated by gemstone spectral CT. NIC has a certain value in differential diagnosis of SCLC and NSCLC. Section II The value of spectral CT in evaluation of lymph nodes metastasis of lung cancerObjective:To detect the usefulness of gemstone spectral CT in diagnosis of lymph node metastasis of lung cancer.Methods:40mediastinal lymph nodes from27cases of non-small cell lung cancer were involvement in this part. These lymph nodes had pathologic diagnosis with metastases and with no metastases in20cases respectively. The CT values of mono keV, the slopes of the spectral attenuation curve and the NIC of the lymph nodes and the primary lesions were evaluated respectively. The parameters among the primary lesions、the lymph nodes with metastases and with no metastases were analyzed comparatively with SPSS19.0. The ROC curve of the spectral parameters of lymph nodes were calculated. The best cut-off value in the differential diagnosis of mediastinal lymph nodes metastases were obtained. To establish a logistic regression model for diagnosis of lymph node metastases and to assess the diagnostic value of the model.Results:The spectral parameters had no statistical differences between lymph nodes metastases in squamous cell carcinoma and in adenocarcinoma (P>0.05). A good correlation had been showed between metastatic lymph nodes and primary lesions in the IC value, NIC value, iodine-water concentration ratio and the slope (r≥0.50, P <0.05). These parameters had no correlation between non metastatic lymph node and primary lesions. There were significant differences between metastases group and non metastases group in the IC values, NIC values and the slopes. The ROC analysis showed that these spectral parameters had a good accuracy in the diagnosis of lymph nodes metastasis. The sensitivity, specificity and accuracy of IC values in diagnosing mediastinal lymph nodes metastases were80%.65%and73%, of the NIC values were75%,75%and75%,of the slope(40-70keV) were85%,65%and75%,of the slope (40-90keV) were75%,65%and70%, respectively. Compared with the short diameter, the spectral parameters had a higher sensitivity but a lower specificity. The slope (40-70keV) and the short diameter entered the logistic regression model. Z test showed that the AUC of the combined index (0.885) was higher than the AUC of short diameter (P=0.036). The sensitivity, specificity, PPV, NPV and accuracy of combined index was75%,95%,94%,79%and85%.Conclusion:The spectral parameter had a high sensitivity but low specificity in diagnosis of lymph node metastases. The spectral parameter combined with the short diameter can improve the accuracy of diagnosis. Spectral CT had a certain value in diagnosis of mediastinal lymph node metastases.