Can quantitative diffusion-weighted MR imaging differentiate between different subtypes of benign and malignant solitary thyroid nodules?

Abstract

Background: Diffusion-weighted MR imaging (DWI) is sensitive to changes in the microstructural organization of tissue that may influence water diffusion. It has been utilized in various forms to evaluate head and neck tumors. The apparent diffusion coefficient (ADC) value is a quantitative parameter for distinguishing malignant from benign thyroid nodule. Determination of different pathologic types of the thyroid nodules is crucial for appropriate therapeutic approach. Our point was to assess the utility of apparent diffusion coefficient values in discriminating different subtypes of benign and malignant solitary thyroid nodules using diffusion MRI with pathological correlation. Results: This prospective study included 73 patients who had thyroid nodules. The size of the investigated lesions ranged from 0.6 to 3 cm. Most nodules were benign (79.45%), and most of these benign nodules were adenomatous nodules. There was a significant difference in ADC values of benign and malignant thyroid nodules (P 0.0001), with the mean ADC value for the benign group (1.7 ± 0.12 × 10-3) higher than that for malignant nodule (0.71 ± 0.15 × 10). The sensitivity, specificity, and accuracy of ADC in differentiating between benign and malignant thyroid nodules were 97.5, 94.4, and 99.2%, respectively. We noticed a significant overlap in the ADC value of pathological subtypes and upon reviewing the pathological results, we found insignificant differences in the ADC values of the various subtypes of malignant and benign nodules, with P value ranging from 0.054 to 0.062 between different pathological subtypes. A significant difference was only noted between non-complicated cysts and solid nodules P 0.0001. In our series, an ADC value of 0.92 × 10-3 mm2/s or less could be used as an indicator of malignancy, with a sensitivity of 97.5%, a specificity of 94.4%, and an accuracy of 99.2%. Conclusion: Diffusion MRI including ADC values are helpful in differentiation between benign and malignant thyroid nodules but not helpful in differentiating between different subtypes of benign and malignant nodules.