18 F-FDG-PET/MRI in patients with Graves’ orbitopathy.

Abstract

Purpose Currently, therapeutic management of patients with Graves’ orbitopathy (GO) relies on clinical assessments and MRI. However, monitoring of inflammation remains difficult since external inflammatory signs do not necessarily represent the orbital disease activity. Therefore, we aimed to evaluate the diagnostic value of 18F-FDG-PET/MRI to assess the inflammation of GO patients. Methods Enrolled patients with new onset of GO underwent ophthalmological examinations to evaluate the activity (CAS) and severity of GO (NOSPECS), as well as an 18F-FDG-PET/MRI (Siemens Biograph mMR) with dual time point imaging (immediately post-injection and 60 min p.i.). A subset of PET parameters including maximum standardized uptake value (SUVmax), metabolic target volume (MTV), and total lesion glycolysis (TLG) were obtained separately per eye and per extraocular eye muscle (EOM). EOM thickness was measured on the co-registered MRI. Results Of 14 enrolled patients, three showed mild, seven moderate-to-severe, and four sight-threatening GO. Patients with severe GO showed statistically significant higher TLG than patients with mild GO (p = 0.02) and higher MTV than patients with mild (p = 0.03) and moderate (p = 0.04) GO. Correlation between NOSPECS on one hand and MTV and TLG on the other was significant (R2 = 0.49–0.61). Conclusion TLG and MTV derived from FDG-PET appear to be good discriminators for severe vs. mild-to-moderate GO and show a significant correlation with NOSPECS. As expected, PET parameters of individual eye muscles were not correlated with associated eye motility, since fibrosis, and not inflammation, is mainly responsible for restricted motility. In conclusion, 18F-FDG-PET/MRI can be used for assessment of GO inflammation.

Imaging of the medial rectus muscle predicts the development of optic neuropathy in thyroid eye disease

“…Heterogeneity has not only been reported for clinical and radiological findings in EO, but also different imaging modalities including MRI and PET (alone or in combination with MRI or CT) have been used to study various morphological and functional parameters. In a recently published work, Weber et al reported PET-MRI to be suited for the assessment of EO inflammation and to be a good discriminator for severe vs. mild-to-moderate EO 25 . A variety of other parameters have been analyzed in EO in numerous other studies.…”

Predictive markers for anti-inflammatory treatment response in thyroid eye disease

“…In conclusion, while cost and patient accessibility pose current challenges ( 81 ), ongoing efforts to enhance SPECT’s availability, coupled with its evolving performance, underscore its potential in predicting responses to anti-inflammatory treatments in patients with TED. In comparison, research progress of PET is still restricted to disease diagnosis and monitoring, which might be mainly due to lack of sample size in PET examination ( 82 , 83 ). Nevertheless, recent research has revealed the potential of Zirconium-89-rituximab PET/CT as a predictive marker for rituximab treatment response in TED ( 84 , 85 ), which might provide insights for future research into further exploring the potency of PET in predicting anti-inflammatory treatment response.…”

Current imaging methods for assessing Graves` orbitopathy activity with particular emphasis on FDG-PET

“…PET/MRI is currently not recommended for clinical use but it can serve as an academic tool to explain the pathophysiology of GO. Technical progress towards shorter protocols and new tracers that are less sensitive to confounding might enable the diagnosis of GO in PET/ MRI in the future (36).…”