Dual-Energy Spectral CT For Evaluating Rectal Cancers With And Without Vascular Invasion

Objective:To investigatethe the potential value of dual-energy CT?DECT?in differentiating vascular invasion rectal cancers from non-vascular invasion rectal cancers using CT scan and dynamic enhancement of iodine concentration and effective atomic number.Material and Methods:78 consecutive untreated patients?47 men,30 women;age range,30-81 years;mean age,63 years?during January 2011 to December 2018 were enrolled and underwent DECT before surgical pathology in our hospital.There were 19 cases in T₃ and 59 cases in T₄.According to whether there is vascular invasion,it is divided into vascular invasione group and non-vascular invasion group.Pathological results showed that there were 39 vascular invasion rectal cancer and 39 non-vascular invasion rectal cancer.ALL patients with rectal adenocarcinoma underwent unenhanced and enhanced CT scan by discover CT750 HD,all images were processed by gemstone spectral imagingmode,and the monoenergetic images in both arterial phases,venous phases and delay phases were obtained.The spectral images were analyzed with GSI Viewer.Dual-energy spectral CT included the level of bilateral anterior superior iliac spine to the level of the lower edge of the pubic symphysis.Selecting three regions of interest at rectal lesion of the average values were recorded.The mean value of iodine?water?concentration?iodine?water?concentration,IC?and effective atomic number?Zeffective atomic number,eff-Z?were measured.Statistical analysis was performed using SPSS 17.0 statistical analysis software.Data were analyzed statistically by the independent-samples t test and were correlated with pathological findings.The receiver operating characteristics?ROC?analysis was also carried to evaluate the efficacy of these parameters for differentiating rectal cancers with or without vascular invasion included sensitivity,specificity,positive predictive value,negative predictive value,accuracy rate and optimal threshold.This study has obtained the standards of the hospital ethics committee.Results:The iodine?water?concentration values of the vascular invasion rectal cancer in the arterial phases were 2.13±0.63mg/ml higher than that of the non-vascular invasion rectal cancer with 1.82±0.58 mg/ml?t=2.241,P=0.028?.The iodine?water?concentration values of the vascular invasion rectal cancer in the venous phases were2.47±0.47mg/ml,significantly higher than that of the non-vascular invasion rectal cancer with 2.17±0.37 mg/ml?t=3.166,P=0.002?.The iodine?water?concentration values of the vascular invasion rectal cancer in the delay phases were 2.20±0.51 mg/ml,which was also higher than that of the non-vascular invasion rectal cancer with1.98±0.37 mg/ml?t=2.202,P=0.031?.The Z effective atomic number values of the vascular invasion rectal cancer were 7.98±0.23 higher than that of the non-vascular invasion rectal cancer with 7.83±0.24?t=2.865,P=0.005?.Based on the ROC curves was 0.650,the optimal cut off value for the IC in the arterial phases was 1.64 mg/ml which yielded a sensitivity of 82.1%and,a specificity of 51.3%,a positive predictive value of 62.7%,a negative predictive value of 70.3%and the accuracy of 65.5%for differentiating rectal cancers with or without vascular invasion.Based on the ROC curves was 0.710,the optimal cut off value for the IC in the venous phases was 2.25mg/ml which yielded a sensitivity of 79.5%and,a specificity of 64.1%,a positive predictive value of 70.5%,a negative predictive value of 75.8%and the accuracy of71.8%for differentiating rectal cancers with or without vascular invasion.Based on the ROC curves was 0.655,the optimal cut off value for the IC in the delay phases was 2.04mg/ml which yielded a sensitivity of 71.8%and,a specificity of 64.1%,a positive predictive value of 68.3%,a negative predictive value of 69.4%and the accuracy of67.9%for differentiating rectal cancers with or without vascular invasion.Based on the ROC curves was 0.685,the optimal cut off value for the Z effective atomic number values was 8.00 mg/ml which yielded a sensitivity of 53.8%and,a specificity of 79.5%,a positive predictive value of 72.4%,a negative predictive value of 63.3%and the accuracy of 65.6%for differentiating rectal cancers with or without vascular invasion.Conclusion:It is feasible to differentiate a vascular invasion rectal cancer from the non-vascular invasion rectal cancer using dual energy CT,especially the iodine concentration measurement in the venous phase.