Quantitative Analysis of Inflammation in Orbital Fat of Thyroid-Associated Ophthalmopathy Using MRI Signal Intensity
Tomoaki T. Higashiyama, MD; Maki M. Iwasa, MD; Masahito M. Ohji, MD
Shiga University of Medical Science
Introduction: We quantitatively analyze the inflammation in orbital fat seen in conjunction with thyroid-associated ophthalmopathy (TAO) using short-tau inversion recovery (STIR) sequences of magnetic resonance imaging (MRI).
Methods: The signal intensities of orbital fat and the superior rectus (SR), inferior rectus (IR), lateral rectus (LR), medial rectus (MR), and superior oblique (SO) muscles on STIR images were measured in 70 eyes of 70 treatment-naive TAO patients and 20 eyes of 20 controls. The signal intensity ratio (SIR) of each tissue and brain white matter was calculated.
Results: The mean SIRs of orbital fat were 1.77 ± 0.23 in TAO patients and 1.65 ± 0.16 in controls. The mean SIR in TAO patients was significantly higher than that in controls (P = 0.04). The mean SIRs in TAO patients were 1.99 ± 0.73, 2.23 ± 0.69, 1.86 ± 0.39, 2.10 ± 0.51, and 1.73 ± 0.43 in the SR, IR, LR, MR, and SO muscles, respectively. The SIR of orbital fat showed significant (P < 0.001) positive correlations with those of the extraocular muscles: SR (r = 0.64), IR (r = 0.55), LR (r = 0.58), MR (r = 0.71), SO (r = 0.65).
Discussion: The noninvasive use of STIR sequences of MRI to evaluate the signal intensity of inflammation in orbital fat quantitatively is useful in TAO patients.
Conclusion: The inflammation in orbital fat might develop in conjunction with inflammation in extraocular muscles.
References: Higashiyama T, Nishida Y, Morino K, et al. Use of MRI signal intensity of extraocular muscles to evaluate methylprednisolone pulse therapy in thyroid-associated ophthalmopathy. Jpn J Ophthalmol 2015;59:124-130.