Applying Amide Proton Transfer-weighted Imaging To Distinguish Papillary Thyroid Carcinomas And Predominantly Solid Adenomatous Nodules:comparison With Diffusion-weighted Imaging

BackgroundNodular goiters and adenomas are the most common benign thyroid nodules,and papillary thyroid carcinoma is the most common malignant thyroid tumors.Nodular goiters and adenomas are usually treated by clinical observation,especially in the elderly.In contrast,the optimal treatment for papillary thyroid carcinoma is surgical excision.Therefore,the precise preoperative differentiation of nodular goiter or adenoma and papillary thyroid carcinoma is of significant practical relevance.Diffusion-weighted imaging provides a better characterization of tissues because it can reflect the random motion of water molecules,which is disturbed by intracellular macromolecules.Previous studies have evaluated the role of diffusion-weighted imaging in differentiating benign from malignant thyroid nodules.Amide proton transfer-weighted(ATPw)imaging is a novel magnetic resonance imaging(MRI)technique that can detect mobile proteins and peptides that contain abundant amide(-NH)chemical constituents.The APTw values can reflect the concentrations of mobile macromolecules,such as proteins and peptides.Investigators in recent human studies have reported preliminary APT findings in the breast,prostate,cervix,rectum,and lung.APTw values were higher in cancers than in normal tissues or benign tumors,and APTw levels varied between different malignant tumors groups or different histological grades.ObjectiveTo study the feature of APTw imaging in thyroid.We want to explore the diagnostic performance of amide proton transfer-weighted(APTw)imaging and diffusion-weighted imaging in differentiating papillary thyroid carcinoma from predominantly solid adenomatous nodule.Materials and MethodsThis study included 24 cases of solitary papillary thyroid carcinoma,and 20 cases of solid adenomatous nodules.Normal thyroid tissues were examined in 12 healthy subjects.The healthy subjects,8 cases of adenomatous nodule with cystic degeneration,and 12 cases of thyroid goiter,were only considered in the descriptive analysis,not included in our statistical analysis.The mean APTw value and the apparent diffusion coefficients(ADCs)of papillary thyroid carcinoma and solid adenomatous nodule were compared via a Mann-Whitney U test and receiver operating characteristic(ROC)-curve analyses.ResultsThe adenomatous nodule(3.27±1.30%)exhibited significantly higher APTw value(p<0.05)than that of the papillary thyroid carcinoma(1.80 ± 0.65%).The optimal cut-off value of the mean APTw value in differentiating papillary thyroid carcinoma from adenomatous nodule was 3.15%,with a sensitivity of 60%and a specificity of 100%.The mean ADC of papillary thyroid carcinoma(1.24 ± 0.24 ×10-3 mm2/s)was significantly lower than that of adenomatous nodule(1.98± 0.38 ×10-3 mm2/s).The optimal cut-off value of the mean ADC was 1.35 × 10-3 mm2/s,with a sensitivity of 100%and a specificity of 75%.Based on the ROC-curve analysis of APT and ADC,the ADC showed a higher area under the curve(AUC)than that of APT(AUCAPT=0.835,AUCADC=0.950).ConclusionAPTw imaging may be useful for the differentiation of papillary thyroid carcinoma from predominantly solid adenomatous nodule.DWI had higher accuracy and sensitivity but lower specificity than APTw imaging.From our present results,we hypothesize that plentiful blood supply may be the main reason why the APTw value of the typical adenomatous nodule is higher than that of papillary thyroid carcinoma.