X031

Diffusion-weighted Magnetic Resonance Imaging (DWI MRI) provides a quantitative measure of disease activity and can be used as an adjunct to clinical assessment in Graves’ Orbitopathy (GO)

Claire Feeney, Farzana Rahman, Ravi Lingam, Vickie Lee, Central Middlesex Hospital, London Northwest Healthcare NHS Trust

Early diagnosis and treatment of Graves’ orbitopathy (GO) are essential to prevent physical and psychological burdens of advanced disease. MRI diffusion weighted imaging (DWI MRI) is an emerging modality to assist with timely diagnosis. We investigated the value of DWI MRI in early diagnosis and monitoring and its relationship with the clinical activity score (CAS) in a multidisciplinary thyroid eye clinic at Central Middlesex Hospital.

Methods: Ninety-one patients were referred to the clinic between 2011 and 2016. Forty-seven had clinical indices of orbital involvement and underwent MRI DWI imaging. Of these, 20 patients had at least one further scan during the course of the disease. The apparent diffusion coefficient (ADC) was calculated for the most affected muscle on each DWI scan and correlated with CAS.

Results: Thirteen patients received intravenous methylpredisolone, 5/20 completed orbital radiotherapy and 3/20 had an orbital decompression during monitoring. The most active muscle at presentation was the right inferior rectus (n=7, 35%).

Mean CAS at presentation was 2.3/7, followed by CAS 1.2, 0.8 and 0.0 at scan 2, 3 & 4 respectively. Mean ADC value fell over the disease course during treatment from 1120.5 to 766.5. A positive correlation was found between initial CAS and ADC (r=0.45, p=0.04). All patients who did not subsequently develop significant disease had ADC values <1000 (mean 674.7) at baseline.

Conclusions: We present a positive correlation between orbital DWI MRI and CAS in GO. DWI MRI may offer predictive benefit in GO. High ADC values identified prior to other clinical disease parameters may help target patients at high risk of developing severe GO. DWI may also serve as a valuable adjunct in early diagnosis and monitoring with potential to identify low risk groups whereby low CAS at baseline combined with DWI <1000 may predict a relatively quiet disease course.