Investigation on the value of spectral CT imaging in diagnosis of benign and malignant thyroid nodules

Objective To explore the value of gemstone spectral imaging (GSI) in the detection and differential diagnosis of benign and malignant thyroid nodules.Methods The spectral CT images in 88 patients with thyroid nodules were analyzed retrospectively.All the patients underwent spectral CT scanning,including 33 patients undergoing biphase enhanced CT imaging.Nodules were divided into benign and malignant ones according to histopathologic results.The iodine concentration,slope of spectral curve,effective atomic number in non-enhanced and enhanced scanning were compared between benign and malignant group by the Wilcoxon rank sum test,respectively.The optimal iodine concentration threshold to predict malignancy was obtained by receiver operating characteristic curve (ROC),sensitivity and specificity were achieved.Results A total of 106 nodules were detected,including 76 benign and 30 malignant nodules.In non-contrast CT imaging,the average iodine concentration,slope of spectral curve,effective atomic number of were 2.35 × 100 μg/ml,0.29 and 7.71 for benign group:-0.51 × 100 μg/ml,-0.06 and 7.52 for malignant group (Z value were-3.072,-3.107 and-3.055,respectively ; P ＜ 0.05).In the arterial phase,the average iodine concentration,slope of spectral curve,effective atomic number of the two group were 27.22 × 100 μg/ml,3.23 and 9.10 for benign group; 18.81 × 100 μg/ml,2.24 and 8.69 for malignant group (Z value were-2.582,-2.582 and-2.564,respectively; P ＜ 0.05).In venous phase,no significant difference was found for each parameter between the two groups (P ＞ 0.05).The optimal iodine concentration to predict malignancy was-0.35 × 100 μg/ml in non-enhanced phase with 56.7％ sensitivity and 73.7％ specificity.The optimal iodine concentration was 22.91 × 100 μg/ml in arterial phase,with 76.2％ sensitivity and 75.0％ specificity.Using iodine concentration to predict malignancy in both noncontrast phase and arterial phase,the sensitivity and specificity were 81.2％ and 73.3％,while the accuracy was 81.6％.Conclusion Gemstone spectral CT imaging can quantitatively evaluate the iodine content of thyroid nodules,having a potential value in differential diagnosis of thyroid nodules. Key words: Thyroid nodule ;  Tomography, X-ray computed ;  Comparative study