Correlation of dualenergy computed tomography findings with histopathology results in neck lymphadenopathies

The head and neck region is rich in lymph nodes and cervical lymphadenopathy owing to various causes is very common. Imaging is frequently requested to confirm the presence of cervical lymphadenopathy,differentiate lymph nodes from otherneck masses, characterize the nodes asbenign or malignant, and aid in identification ofthe cause. However,imaging of cervical lymph nodes represents a true challenge. The presence of nodal metastases is one of the most important prognostic factors in patients with head and neck carcinoma and requires accurate diagnosis. The sensitivity and specificity of different imaging modalities for diagnosis of cervical lymph node metastases is limited. Dual-energy CT (DECT) scanning is an advanced form of CT scanning in which image acquisition is performed at 2 different energies, enabling generation of additional reconstructions and quantitative analysis not possible with single energy CT.The aim of this study is to evaluate the diagnostic performance of the DEBT method in differentiating malignant and benign cervical lymph nodes in patients with head and neck carcinomas. Material and methods Fifty-two patients with diagnosed head and neck carcinoma who underwent contrast-enhanced DECT of the neck were retrospectively evaluated. Fifty-two metastatic lymph nodes and 28 reactive lymph nodes were revealed in histopathological evaluation. Iodine mapping-derived iodine concentration (mg/mL) and normalized monoenergetic attenuation values were obtained via circular regions of interest within metastatic and reactive cervical lymph nodes. Iodine concentrations and normalized Hounsfield unit (HU) values were compared in malignant and reactive lymph nodes. A receiver operating characteristic (ROC) curve was used to determine the sensitivity and specificity of iodine concentration and normalized HU for diagnosis of metastatic nodes. Results The mean age of patients was 60.6 ± 11.8 years (range 19-87 years).The female / male ratio was 0.3 / 1.The iodine concentration of metastatic lymph nodes (27 squamous cell carcinoma, 19 lymphoma and 6 papillary thyroid carcinoma) was significantly lower than reactive lymph nodes (1.45 vs 1.85 mg/ml, p=0.011). Although there was some difference in normalized HU values between metastatic and reactive lymph nodes, this difference was not significant(117 vs 111 HU, p=0.328). A nodal iodine threshold of ≤1.62 mg/ml showed a sensitivity of 71% and a specificity of 77%, (AUC=0.673, 95%CI 0,54-0,80, p=0.011)without histological distinction. Iodine concentration was lower in lymph nodes with metastasis of squamous cell carcinoma than in reactive lymph nodes (1.33 vs 1.85 mg/ml, p<0.001, and higher in those with papillary thyroid carcinoma metastasis (2.39 vs 1.85 mg/ml, p=0.038). Conclusion DECT-derived quantitative iodine data may improve the diagnostic accuracy of computed tomography for nodal metastasis in patients with head and neck carcinoma. More accurate results can be obtained when evaluated together with the iodine concentration according to the primary tumor type, especially in cases where there is doubt about the size of the morphological evaluation. Key words: Head and neck carcinoma, Cervical lymphadenopathy, Dual energy CT, Iodine mapping