Value of magnetic resonance imaging combined with multiple-detector CT in diagnosis of extrathyroid invasion in papillary thyroid carcinoma

Objective To evaluate the diagnostic value of magnetic resonance imaging （MRI） combined with multiple-detector CT （MDCT） for extrathyroid invasion （ETE） of papillary thyroid carcinoma （PTC）. Methods 80 patients with PTC who underwent surgical resection were recruited and divided into the non-ETE group （n = 46） and ETE group （n = 34） according to the pathological diagnosis. All patients underwent routine MRI examination, dynamic contrast-enhanced scanning and diffusion-weighted imaging （DWI） sequence scanning before operation. Apparent diffusion coefficient （ADC）, distribution diffusion coefficient （DDC） and stretch factor （α） were obtained. Results The ADC, DDC and α values in the ETE group were significantly lower than those in the non-ETE group （all P<0.05）. The PS/ES value in the ETE group was significantly lower than that in the non-ETE group （P<0.05）. ROC curve analysis showed that the areas under the ROC curve （AUCs） of ADC, DDC and α for predicting ETE in PTC patients were 0.855, 0.895 and 0.759, respectively. The AUC of the three combined for predicting ETE in PTC patients was 0.951. The sensitivity was 85.00%, and the specificity was 92.50%. The AUCs of PS/ES and △CT values for predicting ETE in PTC patients were 0.683 and 0.840, and 0.901 for the two combined. The sensitivity was 80.00%, and the specificity was 85.00%. The AUC of MRI combined with MDCT for predicting ETE in PTC patients was 0.982, which was higher than that detected by MDCT index combined with each individual index. Conclusions The ADC, DDC and α values measured by preoperative MRI, and PS/ES and △CT values measured by MDCT can be used as reference indexes for evaluating ETE in PTC patients. The diagnostic value of MRI combined with MDCT is the highest.