Application Value Of Dual-energy Spectral CT In The Preoperative Diagnosis Of Cervical Lymph Nodes Metastasis Of Papillary Thyroid Cancer

ObjectiveTo quantitatively assess the diagnostic value of dual-energy computed tomography?CT?imaging for cervical lymph nodes metastasis in patients with papillary thyroid cancer?PTC?.MethodsThis study was approved by the ethics committee and all patients provided written informed consent.Fifty-five consecutive patients with suspected of thyroid cancer were prospectively enrolled and underwent enhanced dual-energy spectral CT scan from August 2016 to May 2017.The quantitative dual-energy CT imaging and qualitative conventional CT scanning data were analyzed and compared by different groups of radiologists.A region of interest was drawn in the cervical lymph nodes with a maximal short axial diameter of greater than or equal to 5 mm.The normalized iodine concentration ratio?NIC?and the slope of the spectral Hounsfield unit curve(?_HU)during both arterial and venous phases were measured respectively from iodine overlay images and spectral curves.Two-sample t test was performed to compare quantitative parameters at dual-energy CT between the histopathologically proven benign and metastatic lymph nodes.Receiver operating characteristic curves were generated for sensitivity and specificity analyses as well as evaluating the diagnostic value of dual-energy CT imaging and conventional CT features.ResultA total of 212 nodes were detected,including 88 benign and 124 metastatic lymph nodes which were successfully matched and labeled during surgery.?1?The conventional CT features including node size,degree and pattern of enhancement,necrosis,as well as extra-nodal extension can be used for detection of metastatic lymph nodes of PTC.The best qualitative parameter for detection of lymph nodes metastasis was strong enhancement in lymph nodes,with sensitivity,specificity and accuracy were 79.0%,63.6%and 72.6%,respectively.By using the other conventional CT features for detection of lymph nodes metastasis,sensitivity,specificity and accuracy were 4%-45.2%,71.6%-100%and 43.9%-57.1%,respectively.?2?Both arterial and venous phase NIC and?_HUU were significantly higher in metastatic than in benign lymph nodes?P<0.001?.?3?The area under curve?AUC?of arterial phase NIC and?_HUU were significantly higher than those of venous phases?P<0.001?.?4?Arterial phase NIC,arterial phase?_HUU and venous phase?_HUU had great value of diagnosis for cervical lymph nodes metastasis in the patients with papillary thyroid Cancer.With optimal threshold arterial phase NIC?25.8%?,arterial phase?_HU?1.139?and venous phase?_HU?1.362?,the sensitivity were 90.3%vs 87.9%vs 82.3%and specificity were 96.6%vs 98.9%vs 95.5%and AUC were 0.986vs 0.976 vs 0.913,respectively.Venous phase NIC had the moderate value,with optimal threshold of 50.9%,the sensitivity,specificity,AUC of venous phase NIC were 87.1%,79.5%,0.897,respectively.ConclusionCompared with qualitative conventional CT features,quantitative parameters associated with NIC and?_HUU at dual-energy CT showed higher accuracy and better diagnostic performance for cervical lymph nodes metastasis in patients with papillary thyroid cancer.