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S. C. Barbarino, S. A. Lauer, E. Kim; T2 Weighted Stir Sequence Mri’S Appear to Offer an Objective and Reproducible Means of Measuring Orbital Edema. Invest. Ophthalmol. Vis. Sci. 2009;50(13):320.
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© ARVO (1962-2015); The Authors (2016-present)
The process for measuring water content in orbital structures using T2 weighted STIR sequence MRI will be demonstrated. Measurements taken from the cerebrospinal fluid and vitreous were separately analyzed, using a .024 mm2 region of interest. Fifteen measurements were taken from each structure, comparing side to side, slice to slice, views, images and patients, from six representative T2 STIR MRI’s from patients with thyroid eye disease. Comparisons were made for 99% confidence intervals.
The range of values for cerebrospinal fluid and vitreous was wider than has previously been observed for rectus muscle, temporalis muscle and temporal bone, particularly between patients. For the vitreous values ranged from 329.3 ± 2.2 (mean ± standard deviation) to 600.9 ± 12.2 with 99% confidence intervals spanning a range from 12-67 units. For cerebsrospinal fluid values ranged from 309 ± 1.7 to 514 ± 8.9 with 99% confidence intervals spanning a range from 6-48 units. Comparison between sides and between images were in a fairly narrow range.
The observed variability in the vitreous may represent differing degrees of liquefaction, while variability in the cerebrospinal fluid may represent differing flow rates through the ventricles. T2 weighted STIR sequence MRI’s are readily available and appear to offer an objective and reproducible means of measuring orbital edema. Further study is needed to establish normal values in the non-TED orbit.
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