Dixon MRI-based quantitative parameters of extraocular muscles, intraorbital fat, and lacrimal glands for staging thyroid-associated ophthalmopathy

Abstract

Objective: To investigate the value of Dixon magnetic resonance imaging (MRI)-based quantitative parameters of extraocular muscles (EOMs), intraorbital fat (IF), and lacrimal glands (LGs) in staging patients with thyroid-associated ophthalmopathy (TAO).

Methods: Two hundred patients with TAO (211 active and 189 inactive eyes) who underwent Dixon MRI for pretreatment evaluation were retrospectively enrolled and divided into training (169 active and 151 inactive eyes) and validation (42 active and 38 inactive eyes) cohorts. The maximum, mean, and minimum values of the signal intensity ratio (SIR), fat fraction (FF), and water fraction (WF) of EOMs, IF, and LGs were measured and compared between the active and inactive groups in the training cohort. Binary logistic regression analysis, receiver operating characteristic curve analysis, and the Delong test were used for further statistical analyses, as appropriate.

Results: Compared with inactive TAOs, active TAOs demonstrated significantly greater EOM-SIR_max, EOM-SIR_mean, EOM-SIR_min, IF-SIR_max, IF-SIR_mean, LG-SIR_max, LG-SIR_mean, EOM-WF_mean, EOM-WF_min, IF-WF_max, IF-WF_mean, and LG-WF_mean and lower EOM-FF_max, EOM-FF_mean, IF-FF_mean, IF-FF_min, and LG-FF_mean values (all p < 0.05). The EOM-SIR_mean, LG-SIR_mean, and LG-FF_mean values were independently associated with active TAO (all p < 0.05). The combination of the EOM-SIR_mean, LG-SIR_mean, and LG-FF_mean values showed better performance than the EOM-SIR_mean value alone in staging TAO in both the training (AUC, 0.820 vs 0.793; p = 0.016) and validation (AUC, 0.751 vs 0.733, p = 0.341) cohorts.

Conclusion: Dixon MRI-based parameters of EOMs, LGs, and IF are useful for differentiating active from inactive TAO. The integration of multiple parameters can further improve staging performance.

Critical relevance statement: In this study, the authors explored the combined value of quantitative parameters of EOMs, IF, and LGs derived from Dixon MRI in staging TAO patients, which can support the establishment of a proper therapeutic plan.

Key points: The quantitative parameters of EOMs, LGs, and IF are useful for staging TAO. The EOM-SIR_mean, LG-SIR_mean, and LG-FF_mean values were found to independently correlate with active TAO. Joint evaluation of orbital tissue improved the ability to assess TAO activity.

Keywords: Dixon magnetic resonance imaging; Extraocular muscle; Intraorbital fat; Lacrimal gland; Thyroid-associated ophthalmopathy.

Fig. 1

Flowchart of patient enrollment and scheme for analysis. TAO, thyroid-associated ophthalmopathy; EUGOGO, European Group on Graves’ Orbitopathy

Fig. 2

Schematic diagrams showing the methods used to measure the quantitative parameters of EOMs, LGs, and IF using Dixon MRI. T2 Dixon water image (a, d, g), QFFI (b, e, h), and QWFI (c, f, i) of a 54-year-old female with active TAO. a–c Quantitative measurements of SIR, FF, and WF in the EOM. a A circular ROI (red, 5–10 mm²) was placed in the ipsilateral temporal muscle. d–f Quantitative IF measurements of the SIR, FF, and WF. g–i Quantitative measurements of the SIR, FF, and WF in the LGs. TAO, thyroid-associated ophthalmopathy; QFFI, quantitative fat fraction image; QWFI, quantitative water fraction image; SIR, signal intensity ratio; FF, fat fraction; WF, water fraction; EOMs, extraocular muscle; IF, intraorbital fat; LG, lacrimal gland

Fig. 3

Representative cases of patients with active and inactive TAO. a–c A 48-year-old man with active TAO and a bilateral CAS of 5. d–f A 50-year-old woman with inactive TAO and a bilateral CAS of 1. The EOM-SIRmean, LG-SIRmean, and LG-FFmean values were 2.865/3.407, 3.661/3.543, and 0.026/0.019, respectively, in the left/right orbit for patients with active TAO (a–c) and 2.330/2.082, 2.183/2.002, and 0.392/0.487, respectively, in the left/right orbit for patients with inactive TAO (d–f)

Fig. 4

Receiver operating characteristic curves of significant parameters for discriminating active from inactive TAO patients in the training (a) and validation (b) cohorts