Evaluation of Activity of Graves' Orbitopathy with Multiparameter Orbital Magnetic Resonance Imaging (MRI)

Background: When quantitative magnetic resonance imaging (MRI) is used to assess the activity of Graves' orbitopathy (GO), the examination is generally focused on a specific orbital tissue, especially the extraocular muscles (EOMs). However, GO usually involves the entire intraorbital soft tissue. The aim of this study was to use multiparameter MRI on multiple orbital tissues to distinguish the active and inactive GO.

Methods: From May 2021 to March 2022, consecutive patients with GO were prospectively enrolled at Peking University People's Hospital (Beijing, China) and divided into those with active disease and those with inactive disease based on a clinical activity score. Patients then underwent MRI, including sequences of conventional imaging, T1 mapping, T2 mapping, and mDIXON Quant. Width, T2 signal intensity ratio (SIR), T1 values, T2 values, and fat fraction of EOMs, as well as water fraction (WF) of orbital fat (OF), were measured. Parameters were compared between the 2 groups, and a combined diagnostic model was constructed using logistic regression analysis. Receiver operating characteristic analysis was used to test the diagnostic performance of the model.

Results: Sixty-eight patients with GO (27 with active GO, 41 with inactive GO) were included in the study. The active GO group had higher values of EOM thickness, T2 SIR, and T2 values, as well as higher WF of OF. The diagnostic model, which included EOM T2 value and WF of OF, demonstrated a good ability to distinguish between active and inactive GO (area under the curve, 0.878; 95% CI: 0.776-0.945; sensitivity, 88.89%; specificity, 75.61%).

Conclusions: A combined model incorporating the T2 value of EOMs and the WF of OF was able to identify cases of active GO, potentially offering an effective and noninvasive method to assess pathological changes in this disease.