Diagnostic Value of Dual-Energy CT Iodine for Characterization of Papillary Thyroid Micro Carcinoma and Better Prediction of Metastatic Cervical Lymph Nodes

The preoperative assessment of cervical lymph node metastasis (LNM) is considered a challenging clinical problem in papillary thyroid microcarcinoma (PTMC) patients. Ultrasonic examination is significant for the cervical LNM in PTMC patients, but there are difficulties and limitations in observing lymph nodes in the cervical central region.

To investigate the diagnostic value of dual-energy CT iodine for characterization of PTMC and better prediction of metastatic cervical lymph nodes of PTMC.

Ninety-five patients with PTMC who underwent dual energy (DE) CT examinations were retrospectively enrolled in the study. The iodine image morphological features of primary tumor were analyzed in the arterial phase and quantitative DECT parameters of the primary tumor were recorded in the arterial and venous phase. Chi-square test and independent-sample t test were performed to compare the differences of morphological features and quantitative parameters of tumors between LNM and non-LNM groups. Receiver operating characteristic curves were generated to assess the diagnostic performance of each DECT parameter and their combinations.

Six primary tumor morphological features of the LNM group demonstrated significant differences compared with the non-LNM group (all p < 0.05). Normalized iodine concentration (NIC) and normalized CT value in the LNM group were significantly higher than those of the non-LNM group in both arterial and venous phase, respectively (all p < 0.001). The area under the curve (AUC) was improved from 0.814 to 0.843 after adding maximum diameter compared with incomplete thyroid capsule alone. In addition, the combination of NICs in arterial and venous phases had higher AUC than other quantitative parameters.

Morphological features and quantitative parameters of DECT are valuable for predicting cervical LNM in patients with PTMC.