3 Tesla Apparent Diffusion Coefficient (ADC) Values of Thyroid Nodules: Prediction of Benignancy and Malignancy

Background: High field strength magnets have the potential to provide good quality diffusion weighted imaging (DWI) sequence images and apparent diffusion coefficient (ADC) maps can give important data for differential diagnosis of thyroid nodules. Objectives: To determine the sensitivity and specificity of ADC values of malignant and benign thyroid nodules at 3 Tesla (T) magnetic resonance imaging (MRI) and to correlate imaging findings with histopathologic results. Patients and Methods: Thirty two patients and 20 healthy volunteers were enrolled in the study. DWI was acquired with b values of 500 and 1000. Mean apparent diffusion coefficient values (ADC(MEAN)) of the nodules and thyroid parenchyma were measured. Nodule ADC(MEAN)/thyroid parenchymal ADC(MEAN) ratio were calculated for each nodule in 25 patients. Results: Thirteen malignant and 63 benign nodules were analysed. The ADC(MEAN) values of malignant nodules were significantly lower than benign nodules in each b value (P < 0.0001). Nodular ADC(MEAN)/thyroid parenchymal ADC(MEAN) ratio was significantly lower in the malignant group at b:500 and b:1000 (P < 0.0001). Considering the selected cut off values (0.98 for b:500 and 0.95 for b:1000) this ratio showed the best performance in differentiation of malignant and benign nodules with a sensitivity of 100% and specificity of 92% -100%. Conclusion: DWI with quantitative ADC measurements is useful in the differentiation of benign and malignant thyroid nodules. The nodule ADC(MEAN)/thyroid parenchyma ADC(MEAN) ratio can be used as an adjunctive parameter in differentiation.