Quantitative Analysis of Orbital Soft Tissues Using Three-Dimensional Fast Spin Echo With 2-Point Dixon-Based Fat Suppression Sequence: Its Association With Methylprednisolone Pulse Therapy Treatment Efficacy in Thyroid-Associated Ophthalmopathy

Background Three-dimensional fast spin echo with 2-point Dixon-based fat suppression (3D-FSE-Dixon) sequence may assess volume and water fraction (WF) of orbit. Purpose To explore the association between 3D-FSE-Dixon based parameters and methylprednisolone pulse therapy (MPPT) efficacy in active moderate-to-severe thyroid-associated ophthalmopathy (TAO). Study Type Retrospective. Population Fifty-nine TAO patients (29 females, 30 males, 49.1 +/- 10.9 years) were included: 26 (15 females, 11 males, 48.4 +/- 11.1 years) showed improvement and 33 (14 females, 19 males, 49.6 +/- 10.9 years) did not. Field Strength/Sequence3D-FSE-Dixon sequence of orbits at 3 T. Assessment Manual segmentation delineated bony orbit (BO), whole orbit (WO), globe (GO), lacrimal gland (LG), and optic nerve (ON). Multi-dimensional threshold (MDT) identified orbital fat (OF). Extraocular muscles (ETM) were obtained by subtracting other tissues from WO. WF was calculated from water and in-phase images. Treatment efficacy, the clinical outcome, was assessed within 2 weeks after MPPT. Statistical Tests Unpaired t-test and Mann-Whitney U test compared normal and non-normal data, respectively. Paired t-test analyzed parameter changes pre- and post-MPPT. Multivariate logistic regression analysis identified factors independently associated with the efficacy of MPPT. Significance was set at P < 0.05. Results Responsive group showed significantly higher pre-treatment WF (ETM, 0.86 +/- 0.06 vs. 0.82 +/- 0.07; OF, 0.21 +/- 0.04 vs. 0.19 +/- 0.02), with no difference in volume (OF: 21.34 +/- 3.33 vs. 21.36 +/- 3.46, P = 1.00; ETM: 13.48 +/- 2.82 vs. 13.72 +/- 3.45, P = 1.00) or volume ratio (OF/GO: 3.23 +/- 0.50 vs. 3.26 +/- 0.56, P = 1.00; ETM/GO: 2.06 +/- 0.58 vs. 2.12 +/- 0.64, P = 1.00). WF significantly decreased in responsive group (ETM, 0.86 +/- 0.06 vs. 0.79 +/- 0.05; OF, 0.21 +/- 0.04 vs. 0.17 +/- 0.03) but not decreased in unresponsive group (ETM, 0.81 +/- 0.07 vs. 0.81 +/- 0.07, P = 1.00; OF, 0.19 +/- 0.02 vs. 0.190 +/- 0.02, P = 1.00). ETM WF and disease duration can assess MPPT efficacy. Data Conclusion Higher ETM WF demonstrates better MPPT efficacy for TAO. Evidence Level4 Technical Efficacy Stage 4