Parameters of dual-energy CT for the differential diagnosis of thyroid nodules and the indirect prediction of lymph node metastasis in thyroid carcinoma: a retrospective diagnostic study

Background: To further investigate the differential diagnosis of thyroid nodules using dual-energy computed tomography (DECT) and explore the relationship between DECT parameters and lymph node metastasis in thyroid carcinoma for clinical practice, especially difficult diagnosis by routine imaging examination. Methods: A total of 150 patients with thyroid nodules who underwent preoperative DECT and Thyroid Imaging Report and Data System (TIRADS) classification were enrolled in this study, including 96 patients with malignant tumors and 54 with benign tumors. The DECT parameters were got form regions of interest (ROI) by an experienced radiologist team and thyroid nodules and lymph node status of all patients were identified by cytology and histopathology. Statistical analyses were performed using Student's t-test, Chisquared test, and receiver operating characteristic (ROC) curves. Results: In the differential diagnosis of benign and malignant thyroid nodules, the optimal iodine concentration (IC) and normalized iodine concentration (NIC) cut-off values were ICa (2.835 mg/mL), NIC1a (0.690), and their corresponding area under the curve (AUC) were 0.940, 0.954 respectively; meantime, the optimal computed tomography (CT) value and slope of the spectral Hounsfield unit curve (1HU) cut-off values were 70 keVa (125.05 HU) and 1HU2a (1.405), and their corresponding AUC were 0.955, 0.941 respectively. For lymph node status (with or without lymph node metastasis), the optimal IC and NIC thresholds were ICa (1.715 mg/mL) and NIC2a (0.155), and their corresponding AUC were 0.717, 0.720 respectively; meanwhile, the optimal CT value and 1HU thresholds were 70 keVv (89.635 HU) and 1HU2v (1.185), and their corresponding AUC were 0.729, 0.641 respectively. Conclusions: Base on our study, we think DECT is useful in differentiating malignant from benign thyroid nodules, which has potential value in the indirect prediction of lymph node metastasis in thyroid carcinoma.