Hashimoto thyroiditis: correlation of MR imaging signal intensity with histopathologic findings and thyroid function test results.

Purpose: To assess the clinical usefulness of magnetic resonance (MR) imaging of the thyroid gland in Hashimoto thyroiditis.

Materials And Methods: Signal intensity ratios on spin-echo T1-, proton-density-, and T2-weighted images were measured prospectively in 37 patients with Hashimoto thyroiditis (33 women, four men; mean age, 51 years) and in 10 patients with thyroid lymphoma (six women, four men; mean age, 68 years). Signal intensity ratios were correlated with histopathologic findings and thyroid function test results with stepwise regression analysis. Diagnosis of lymphoma with signal intensity ratios was compared with morphologic diagnosis by using receiver operating characteristic curves.

Results: A proton-density-weighted signal intensity ratio of 1.54 or higher indicated hypothyroidism (R = .445, P = .008; 29% sensitivity [two of seven patients]). A T2-weighted signal intensity ratio of 5.08 or higher suggested advanced glandular destruction (R = .677, P < .001). Diagnosis by each observer was better than diagnosis with signal intensity ratios.

Conclusion: MR imaging results can reflect thyroid function and histopathologic findings in the thyroid gland and help discriminate malignant lymphoma from Hashimoto thyroiditis.