MR imaging of the thyroid: correlation between apparent diffusion coefficient and thyroid gland scintigraphy.

PURPOSE: To evaluate the usefulness of echo-planar MR imaging for assessing the thyroid function and confirm the clinical use of MR imaging for thyroid diseases.

MATERIALS AND METHODS: Thirty-four patients with a variety of thyroid disorders (24 Graves disease; five subacute thyroiditis; five Hashimoto thyroiditis) were examined using T1-, T2-, and diffusion-weighted magnetic resonance (MR) imaging and thyroid scintigraphy with Tc-99m pertechnetate.

RESULTS: The ADC values obtained from the diffusion-weighted images of the patients with Graves disease were significantly higher than those of patients with subacute hyroiditis and Hashimoto thyroiditis, though no difference among those disorders was observed on T1- and T2-weighted images. Based on the ADC value, anisotropy was not observed in the thyroid gland. An ADC value of 1.82 x 10(-3) mm(2)/second or higher indicated the presence of Graves disease (sensitivity 75%, specificity 80%).

CONCLUSION: Diffusion-weighted MR images may be of value for the diagnosis of thyroid diseases and could be clinically important in the evaluation of thyroid function.