Magnetic Resonance evaluation of disease activity in Graves' ophthalmopathy: T2-time and signal intensity of extraocular muscles.

Background: It is accepted that T2-weighted imaging can demonstrate the extent of an inflammatory process in Graves' ophthalmopathy (GO). This aim of this study was a comparative evaluation of the most commonly used indicators of extraocular muscle pathophysiology, i.e. signal intensity (SI) and T2-time (T2-t) in correlation with muscle volume (MV), and to determine the need to make the above indicators objective with regards to clinical practice. Material/Methods: MRI examinations in a 1.5 T scanner of 40 orbits formed the study group. Quantitative assessment of the muscles was carried out using a numerical segmentation imaging technique (NSI). SI and T2-t were measured for each muscle. A standardization algorithm was applied based on T2-t and IS from the ipsilateral white matter of the frontal lobes. Results: The correlation between T2-t and MV for the medial rectus and inferior rectus muscles (IRM) was at a comparatively high level (R: 0.49 and 0.47), with a value as high as R=0.58 for the superior rectus muscle. Correlation between SI and volume for these muscles was found to be at R-levels of 0.37, 0.48, and 0.46. Correction of the T2-t and SI values with use of a standardization algorithm in most cases did not change the above correlations, except for IRM. Conclusions: The parameter with the higher correlation to the symptoms of GO is T2 The value of SI as an indicator of disease intensity in GO that can be used without the use of multiple echo sequences was confirmed. It is necessary to make the above parameters objective relative to white matter when calculating IS for the inferior rectus muscle.

Keywords: Disease Progression, Adult, Graves Ophthalmopathy - physiopathology, Magnetic Resonance Imaging, Oculomotor Muscles - physiopathology, Statistics as Topic