Comparison of dual-energy CT-derived iodine content and iodine overlay of normal, inflammatory and metastatic squamous cell carcinoma cervical lymph nodes

Objectives To evaluate whether dual-energy computed tomography (DECT)-derived iodine content and iodine overlay could differentiate between normal, inflammatory and metastatic squamous cell carcinoma (SCC) cervical lymph nodes. Methods This study was approved by the institutional review board. Sixteen patients with normal lymph nodes, 20 patients with enlarged nodes draining deep cervical inflammations and 23 patients with pathologically proved metastatic SCC nodes who underwent contrast enhanced DECT were retrospectively identified. Iodine content and overlay of 36 normal, 43 inflammatory and 52 metastatic lymph nodes were calculated using circular regions of interest and compared among the three groups. A receiver operating characteristic (ROC) curve was used to determine the sensitivity and specificity of iodine content and overlay for diagnosis of metastatic nodes. Results Iodine content (mg/ml) was significantly lower for metastatic lymph nodes (2.34+/-0.45) than for normal (2.86+/-0.37) and inflammatory (3.53+/-0.56) lymph nodes, P < 0.0001. Iodine overlay (HU) was also significantly lower for metastatic lymph nodes (47+/-11.6) than normal (57.4+/-8.2) and inflammatory nodes (69.3+/-11.5), P < 0.0001. The areas under the ROC curve for iodine content and iodine overlay were 0.923 and 0.896. Conclusions DECT-derived iodine content and overlay differ significantly among normal, inflammatory and metastatic SCC cervical lymph nodes. Key points Derived iodine content can be calculated from contrast-enhanced dual-energy CT. Derived iodine content and iodine overlay could help characterise cervical lymph nodes. Iodine parameters were significantly lower in metastatic lymph nodes than normal/inflammatory lymph nodes. Iodine content appears more sensitive than iodine overlay for lymph node characterisation.