Diagnostic value of sonography, ultrasound-guided fine-needle aspiration cytology, and diffusion-weighted MRI in the characterization of cold thyroid nodules

Introduction: The purpose of this prospective study was to assess the diagnostic value of different modalities for the characterization of cold thyroid nodules.

Methods: In 35 patients with cold nodules, thyroid carcinoma was suspected on scintigraphy. These patients were prospectively investigated with sonography, ultrasound-guided fine-needle aspiration (USgFNA), and quantitative diffusion-weighted imaging magnetic resonance imaging (DWI) (navigated echo-planar imaging; maximum b-value 800s/mm(2)) prior to surgery. The sonographic findings, USgFNA cytology, and the apparent diffusion coefficient (ADC) values of DWI were correlated with the postoperative histology of benign and malignant lesions. Statistical analysis was performed with the Kruskal-Wallis test and the Fisher's exact test. P<.05 denoted statistical significance.

Results: The accuracy of sonography and USgFNA was 64% and 68.8%, respectively. The sensitivity was 86.7% and 80%, respectively. Specificity was only 57.2% and 50%, respectively. The median ADC values for carcinoma and adenoma were 2.73 x 10(-3)mm(2)/s and 1.93 x 10(-3)mm(2)/s, respectively (P<.001). There was no significant difference between the median ADC value for Hashimoto thyroiditis (3.46 x 10(-3)mm(2)/s) and carcinoma. An ADC value of 2.25 x 10(-3)mm(2)/s or higher was proven to be the cut-off value for differentiating between benign and malignant cold thyroid nodules, with an accuracy of 88%, a sensitivity of 85%, and a specificity of 100%.

Conclusions: These results show that quantitative DWI is a more reliable diagnostic method for differentiation between benign and malignant thyroid lesions than sonography or USgFNA. However, further studies including a larger study population are necessary to confirm our study results.