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S. Bianchi Marzoli, L. Polit, R. Lanzi, C. Godi, G. Cammarata, M. Manzoni, L. Melzi, A. Falini; Magnetic Resonance Imaging Parameters for Evaluation of Activity and Severity of Thyroid Associated Orbitopathy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3915.
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© ARVO (1962-2015); The Authors (2016-present)
To use conventional and Diffusion Weighted Imaging (DWI) Magnetic Resonance Imaging (MRI) to evaluate extraocular muscles (EOMs) involvement in different stages of Thyroid Associated Orbitopathy (TAO).
56 patients with TAO (48 bilateral, 8 unilateral, mean age 53.7 +12.4 years , 16 M, 40 F) and 17 age-matched controls were studied. The Clinical Activity Score (CAS) was applied to identify active (CAS ≤ 3) and inactive ( CAS> 3) TAO. To define severity of disease a score of impairment was assigned to each EOM (1=normal to 4 =severe). MRI study was performed with conventional and DWI sequences. Signal Intensities Ratios (SIRs) from T2-SPIR, post-Gadolinum T1-SPIR (T1Gd) and Apparent Diffusion Coefficient (ADC) were measured by positioning regions of interest (ROI) in each EOM and values were normalized to ipsilateral deep gray matter. MRI values of TAO were compared with controls, CAS and the degree of EOM impairement using Mann-Whitney and Spearmann Correlation Tests.
Statistically significant differences were found for: 1) T2, T1Gd and ADC SIRs between TAO and controls (p < 0.001); 2) T2 and T1Gd SIRs between active and inactive TAO (p = 0.05 and < 0.001 ); 3) T2 and T1Gd between differently impaired EOMs (p< 0.001); 4) ADC SIRs between TAO normally functioning EOMs and controls (p < 0.001).
EOMs in TAO may have higher MRI T2, T1Gd and ADC signals intensities than in controls.T2, T1Gd and ADC signals intensities may be used to differentiate active from inactive EOMs involvement; T2 and T1Gd signal intensities correlate with severity of EOMs impairment while ADC values may identify the early phases of the disease in EOMs with normal function. These data suggest MRI can be helpful as a non-invasive tool in the clinical evaluation of EOMs involvement in TAO.
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