To investigate the quantitative value of the signal intensity ratio of extraocular muscle and ipsilateral white matter measured by MRI for the evaluation of activity in thyroid-associated ophthalmopathy.

A total of 129 patients and 245 eyeballs with thyroid-associated ophthalmopathy were enrolled in this study and this 245 eyeballs were set as thyroid-associated ophthalmopathy group(TAO group). There were 10 patients with newly diagnosed Graves′ disease and in the same period and these 20 eyeballs were set as graves′ disease group(GD group). 32 normal people from annual physical test excluded thyroid and eye diseases and their 64 eyes were selected randomly for the normal control group (NC group). The signal intensity of the extraocular muscle and the ipsilateral white matter on the MRI images were measured, while did exophthalmos and the width of the inner fat of eyeballs(FWs)measurements in the same time.

SIR, FWs, and exophthalmos of TAO group were higher than those of the other 2 groups[SIRs: 1.71(1.40, 2.10)vs 1.26(1.22, 1.34)and 1.23(1.14, 1.32); FWs: 8.04(6.70, 8.71)mm vs 6.16(4.86, 7.08)mm and 6.93(6.41, 7.65)mm, exophthalmos: 20.10(18.56, 22.15)mm vs 15.40(14.87, 16.60)mm and 14.73(13.40, 16.07)mm, all P<0.05]. The reference value of SIR establishing based on SIRs of NC group is less than 1.37. In total 129 TAO patients, 55 patients(with 106 eyeballs)have a clinical activity score(CAS). Then, these eyeballs were grouped to activity and non-activity (grouped by CAS≥3), and the baseline group difference of these 2 groups was not statistically significant. The SIRs and exophthalmos of activity group were higher than the non-activity group[SIRs: 1.70(1.45, 2.33)vs 1.41(1.25, 1.75); exophthalmos: (20.38±2.40)mm vs (19.05±3.70)mm, all P<0.05]. But the difference of FWs of these two groups was not statistically significant(P>0.05). The SIRs and CAS had a positive correlation(r=0.580, P=0.000), through the receiver operating characteristic curve(ROC)we get the best diagnostic performance of TAO activity when the SIR≥1.56(sensibility=65.6%, specificity=89.1%, AUC=0.815, P=0.000).

The signal intensity ratio of extraocular muscle and ipsilateral white matter may discriminate the activity of TAO early as a quantitative indicator, reflecting its efficacy, and is worth clinically generalizing. (Chin J Endocrinol Metab, 2018, 34: 106-111)

Thyroid-associated ophthalmopathy; Signal intensity ratio of extraocular muscle to ipsilateral white matter; Activity evaluation; Quantitative indicator