Objective：To evaluate the application of MRI in the assessment of activity and staging of thyroid-associated ophthalmopathy (TAO). Methods：Eighty-four patients with TAO of double sides (TAO group) were included and assigned into active stage group (n=68) and stable stage group (n=16). Meanwhile, 25 normal people were selected as normal group. MRI orbital scan was performed in each subject to assess the values of exophthalmos，short and long diameters of extraocular muscles. Ratios of short diameter to long diameter of extraocular muscles were calculated. Time of T2 relaxation，T2 signal intensity of extraocular muscles and homonymous temporal muscle were measured to calculate the ratios of T2 signal intensity. Results：Exophthalmos value and ratios of short diameter to long diameter of extraocular muscles of TAO group were significantly higher than those of normal group (P<0.01), while there was no difference between the active and stable groups in these parameters. There were significant differences between active stage group and stable stage group in the time of T2 relaxation and ratios of T2 signal intensity of extraocular muscles (P<0.01). Conclusion: The time of T2 relaxation and ratios of T2 signal intensity of extraocular muscles in MRI are useful parameters to show the clinical activity of TAO and can be considered as the quantitative parameters to assess the activity and staging of TAO.
