Determining Disease Activity and Glucocorticoid Response in Thyroid-Associated Ophthalmopathy: Preliminary Study Using Dynamic Contrast-Enhanced MRI.

Objective: To assess the role of dynamic contrast-enhanced (DCE)-MRI of the extraocular muscles (EOMs) for determining the activity of thyroid-associated ophthalmopathy (TAO) and treatment response to glucocorticoids (GCs).

Materials and methods: We prospectively enrolled 65 patients with TAO (41 active, 82 eyes; 24 inactive, 48 eyes). Twenty-two active patients completed the GC treatment and follow-up assessment, including 15 patients (30 eyes) and 7 patients (14 eyes), defined as responsive and unresponsive, respectively. Model-free (time to peak [TTP], area under the curve [AUC], and Slope_max) and model-based (K^trans, K_ep, and V_e) parameters of EOMs in embedded simplified histogram analyses were calculated and compared between groups. Multivariable logistic regression analysis was used to identify the independent predictors. The area under the receiver operating characteristic curve (AUROC) was used to evaluate the diagnostic performance.

Results: Active patients exhibited significantly higher TTP at the 10th percentile (-10th), TTP-mean, and TTP at the 90th percentile (-90th); AUC-10th, AUC-mean, AUC-90th, and AUC-max; K^trans-10th and K^trans-mean; and V_e-10th, V_e-mean, V_e-90th, and V_e-max than inactive patients (P < 0.05). Responsive patients exhibited significantly lower TTP-min; higher K^trans-mean and K^trans-max; and higher K_ep-10th, K_ep-mean, and K_ep-max than unresponsive patients (P < 0.05). TTP-mean and V_e-mean were independent variables for determining disease activity (P = 0.017 and 0.022, respectively). A combination of the two parameters could determine active TAO with moderate performance (AUROC = 0.687). TTP-min and K^trans-mean were independent predictors of the response to GCs (P = 0.023 and 0.004, respectively), uniting which could determine the response to GCs with decent performance (AUROC = 0.821).

Conclusion: DCE-MRI-derived model-free and model-based parameters of EOMs can assist in the evaluation of TAO. In particular, TTP-mean and V_e-mean could be useful for determining the activity of TAO, whereas TTP-min and K^trans-mean could be promising biomarkers for determining the response to GCs.