Quantitative parameters in iodine overlay image based on dual-source dual-energy computed tomography in differentiating benign and malignant thyroid nodules

Abstract

Objective To investigate the application of quantitative parameters associated with iodine concentration derived from iodine overlay image by dual-source dual-energy computed tomographic (CT) in differentiating benign and malignant thyroid nodules. Methods Seventy-eight patients (total 112 nodules, including 64 benign and 48 malignant nodules) with thyroid nodules who underwent plain scan (PS), arterial phase (AP) and venous phase (VP) enhanced scan by DSCT (80 kVp/Sn140 kVp) were analyzed retrospectively. Iodine overlay images were obtained by the dual energy post-processing software. The mean iodine concentrations in the normal thyroid parenchyma (ICThy), the lesion (ICLes), and the carotid artery(ICCar) of PS, AP and VP were measured from iodine overlay images. The iodine concentration difference (ICD), the iodine concentration difference-to-normal parenchyma ratio (ICDNR) and the normalized iodine concentration ratio (NIC) were calculated. The two-sample t test was performed to compare quantitative parameters between the benign and malignant nodules. ROC curve with quantitative parameters of three phases was used to analyze the diagnostic efficiency of ICD, ICDNR, NIC and ICles. Results During PS, mean ICDNR, ICD and ICLes of malignant nodules were respectively 1.04 ± 0.95, (2.20 ± 1.82) mg/ml, (-0.04±1.65) mg/ml, ICDNR, ICD and ICLes of benign nodules were respectively 0.04 ± 0.41, (0.35 ± 0.97) mg/ml, (2.19 ± 0.55) mg/ml. ICDNR and ICD of malignant nodules were higher than benign nodules (t'=6.63, 6.39, P< 0.05), while ICles of malignant nodules were lower than benign nodules (t=10.13, P< 0.05). During AP, mean ICDNR, ICD, ICLes of malignant nodules were 0.39 ± 0.29, (2.23 ± 1.77) mg/ml, (3.81 ± 1.50) mg/ml, and benign nodules were 0.49 ± 0.22, (2.97 ± 1.91) mg/ml, (3.17± 1.64) mg/ml, respectively. ICDNR, ICD of malignant nodules were lower than benign nodules (t'=2.08, t=2.12; P< 0.05),while ICles of malignant nodules were higher than benign nodules (t=2.12, P< 0.05). During VP, mean NIC of the malignant and benign nodules were 0.45 ± 0.21, 0.58 ± 0.37, respectively. NIC of malignant nodules were lower than benign nodules (t'=2.35, P< 0.05). AUC of ICDNR during PS was 0.892, the sensitivity was 83.3% and the specificity were 90.5%. Conclusion Quantitative parameters associated with iodine concentration by dual-source dual-energy CT may increase the efficiency and accuracy in differentiating benign and malignant thyroid nodules. Key words: Thyroid nodule; Iodine concentration; Tomography, X-ray computed