Diagnostic Accuracy of MRI-Based Dixon and T2 Localization Techniques for Imaging Severity and Progression in Thyroid-Associated Ocular Diseases

Abstract

Background: Thyroid-associated ocular diseases (TAOD) are autoimmune conditions that affect orbital structures, leading to significant morbidity, including diplopia, proptosis, and visual impairment. Accurate assessment of disease severity and progression is crucial for effective management and treatment. The clinical activity score (CAS) and European Group on Graves’ Orbitopathy (EUGOGO) criteria are widely used for assessing TAOD severity and progression. However, these methods rely on subjective evaluations and may not fully capture tissue changes, inflammation, or quantitatively measure fat deposition and muscle involvement. This study evaluates the diagnostic accuracy of magnetic resonance imaging (MRI)-based Dixon and T2 techniques to provide more objective and quantitative assessments of orbital pathology in TAOD. Objectives: The present study aimed to assess the diagnostic accuracy of MRI-based Dixon and T2 techniques in determining the severity and progression of thyroid-associated eye diseases. Patients and Methods: In this retrospective cohort study conducted at Affiliated Lishui Hospital of Zhejiang University, data from 78 patients diagnosed with thyroid-associated ophthalmopathy were analyzed. Patients were categorized based on disease activity and progression using clinical scores. The MRI with Dixon and T2 techniques was employed to evaluate orbital structures. To evaluate the diagnostic accuracy of the MRI-based Dixon and T2 techniques, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated using the CAS as the reference standard. A CAS score of ≥ 3 was used to define the active disease stage, while a CAS score of < 3 indicated the inactive stage. Results: Significant differences were observed in the average extraocular muscle (EOM) water signal intensity (active group: 398.96 ± 102.45; inactive group: 326.70 ± 80.46; t = 3.469; P = 0.001) and average EOM T2 value (ms) (active group: 79.45 ± 7.42; inactive group: 75.60 ± 6.80; t = 2.349; P = 0.021). Greater involvement of orbital fat, EOMs, and lacrimal glands was noted in the active phase and progression groups (P < 0.05). The CAS was positively correlated with the average EOM water fraction (r = 0.456; P = 0.024) and average lacrimal gland signal intensity (r = 0.624; P = 0.001). The results demonstrated high sensitivity and specificity for key parameters, including the average EOM water fraction (sensitivity: 85.7%; specificity: 82.4%), average EOM T2 value (sensitivity: 78.6%; specificity: 76.5%), and average lacrimal gland signal intensity (sensitivity: 89.3%; specificity: 88.2%). Conclusion: Dixon and T2 techniques are valuable for assessing the severity and progression of thyroid-associated eye disease. However, larger sample sizes and longer follow-ups are necessary for further validation and for estimating predictive accuracy, sensitivity, and specificity.