The Value Of DE-CT Enhanced Scan In Differential Diagnosis Of Benign And Malignant Thyroid Nodules

Objectives:1. To investigate the use of dual energy CT (DECT) to differentiate malignant and benign thyroid nodules using iodine map image (IM), normalized iodine concentration (NIC) and spectrum curve slope (SCP) in enhanced scan.2. To improve detection rate of metastatic lymph nodes in thyroid carcinoma by analyzing the parameters of DE-CT. To explore the correlations between malignant of thyroid and metastatic lymphonodus.3. To evaluate effect of non-linear image blending optimal contrast technique with dual-energy CT in thyroid nodules.Methods:1. Two phased DE-CT enhanced scan data (arterial and venous phases) for 180 patients with confirmed pathology results (120 malignant and 60 benign) were retrospectively investigated. Meanwhile every patient satisfied the CT value of internal carotid:300±100Hu at arterial phase and 100±100Hu at venous phase. Nodules with irregular shape, surrounding tissue invasion, uncompleted enhanced ring and small discrete granular calcification were considered to be thyroid carcinoma. Diagnosis sensitivity, specificity and accuracy based on the above morphology features were obtained from the IM images for each nodule and compared with the diagnosis results obtained from conventional CT images. The CT value, normalized iodine concentration (NIC) and SCP were compared between malignant and benign nodules respectively. NIC was defined as the ratio of the nodule IRA value and the supporting artery IRA value.2.120 cases of thyroid cancer cases were confirmed by pathology:(1)54 patients without neck lymph node metastasis, choose the length diameter<1.0cm and have visible door structure of lymph nodes were 44 pieces. (2)66 patients with lymph metastasis, each case only selected with one of the most accurate location and diameter>1.0cm metastatic lymph nodes were 56 pieces. The iodine related attenuation (IRA), CT value and Spectrum Curve(SC) of lymph nodes were measured respectively, calculated NICnod, normalized CT value and SCP value. The differences of NIC, normalized CT value, SCP value between normal and metastatic lymph nodes were compared. Analyzed the correlation of NIC, normalized CT value, SCP value between the thyroid cancer and metastatic lymph nodes.3.94 patients with thyroid nodules underwent contrast-enhanced dual-energy CT neck scan. Images were divided into 4 groups, including 80kV (group A),140kV (group B), linear blending 0.3LB(group C) and non-linear blending NLB(group D). CT value, SNR(signal to noise ratio), CNR(contrast to noise ratio) of arteria carotis, normal thyroid, thyroid nodules and the background noise of image were compared respectively in among 4 groups. The subjective image quality score were compared between C and D.Results:1. The diagnosis sensitivities, specificities and accuracies from IM images of arterial phase based on morphology features of irregular shape, surrounding tissue invasion and uncompleted enhancement ring were significantly better than the diagnosis results based on conventional CT images; while the diagnosis results based on small discrete granular calcification had no significant between IM images(84 malignant,60 benign) and conventional CT images (82 malignant,60 benign). At venous phase, the NIC and normalized CT value for normal, malignant and benign groups (0.99±0.13,0.65±0.21,0.82±0.07, and 1.02±0.14,0.63±0.23,0.84±0.10, respectively) had significant differences (P all<0.05), while those values at arterial phase had no significant differences. When diagnosed malignant tumor, the critical NIC and normalized CT value were 0.76、0.79, the area under ROC curve of AUC value were 0.91,0.92. Combined morphology in IM, NIC, normalized CT value to diagnosis thyroid carcinoma, the sensitivity, specificity, accuracy were 90.00%,93.33%,91.11%.The SCP values for normal, malignant and benign groups (4.71±0.95,3.56±1.05,4.13±1.06, respectively) had significant differences in each group (P all<0.05); at arterial phase, there were no significant difference (P>0.05).2. At artery phase, normal lymph node, metastasis lymph node of NIC (normalized CT value) were 0.13±0.70,0.51±0.18 (0.12±0.46,0.50±0.16); at venous phase were respectively 0.42±0.10,0.68±0.19(0.45±0.11,0.69±0.16); these datas had significant differences (Pall<0.05). NIC and standardized CT values of metastatic lymph nodes were higher than those in the normal group. The SCP values of normal and metastatic lymph nodes at artery (venous) phase were 2.12±0.78 (2.33±0.75),5.52±2.48(3.70±0.96), had significant difference(P<0.01).At venous phase, the correlation coefficient r of NIC, normalized CT and SCP values between thyroid carcinoma and metastasis lymph node were respectively 0.90, 0.88 and 0.90, had large correlation; at arterial phase, the correlation coefficient r were 0.27, 0.22 and 0.44, had poor correlation.3. The background noise of image in group C and D has significant differences (P>0.05), while this data all less than group A and B. CT value of arteria carotis, normal thyroid, thyroid nodules between group A and D have no significant differences (P all>0.05), these datas all more than group B and C. SNR and CNR of arteria carotis, thyroid nodules in group D were higher than in other groups, all have significant differences (P all<0.05). CNR of normal thyroid all have significant difference in each groups, while group D was the highest. The subjective image quality score in group C and D were 3.36±0.51,4.01±0.56, image quality in group D was better than group C(P<0.05).Conclusions:1. Morphology features and quantification values extracted from dual-energy CT data had important value in differentiating thyroid nodules. Dual-energy CT could improve the qualitative diagnosis accuracy of thyroid nodules, have important value to develop therapeutic options.2. At venous phase by DE-CT, the correlations of NIC, normalized CT value and SCP value between thyroid carcinoma and metastatic lymph nodes were large. There is a certain value in differentiating lymph node metastasis of thyroid carcinoma.3. NLB image could improve the image quality of neck, and clear display capsule and internal structure of thyroid nodules, which have value in differentiating malignant from benign thyroid nodules.