Thyroid-Associated Orbitopathy: Evaluating Microstructural Changes of Extraocular Muscles and Optic Nerves Using Readout-Segmented Echo-Planar Imaging-Based Diffusion Tensor Imaging

Abstract

Objective: We aimed to investigate the ability of readout-segmented echo-planar imaging (rs-EPI)-based diffusion tensor imaging (DTI) in assessing the microstructural change of extraocular muscles (EOMs) and optic nerves in patients with thyroidassociated orbitopathy (TAO) as well as in evaluating disease activity. Materials and Methods: We enrolled 35 TAO patients and 22 healthy controls (HCs) who underwent pre-treatment rs-EPIbased DTI. Mean, axial, and radial diffusivity (MD, AD, and RD) and fractional anisotropy (FA) of the medial and lateral EOMs and optic nerve for each orbit were calculated and compared between TAO and HC groups and between active and inactive TAO groups. Factors such as age, sex, disease duration, mediation, and smoking history between groups were also compared. Logistic regression analysis was used to evaluate the predictive value of significant variables for disease activity. Results: Disease duration was significantly shorter in active TAOs than in inactive ones (p < 0.001). TAO patients showed significantly lower FA and higher MD, AD, and RD than HCs for both medial and lateral EOMs (p < 0.001), but not the AD value of lateral EOMs (p = 0.619). Active patients had significantly higher FA, MD, and AD than inactive patients for medial EOMs (p < 0.005), whereas only FA differed significantly in the lateral EOMs (p = 0.018). The MD, AD, and RD of optic nerves were significantly lower in TAO patients than HCs (p < 0.05), except for FA (p = 0.129). Multivariate analysis showed that the MD of medial EOMs and disease duration were significant predictors for disease activity. The combination of these two parameters showed optimal diagnostic efficiency for disease activity (area under the curve, 0.855; sensitivity, 68.4%; specificity, 96.9%). Conclusion: rs-EPI-based DTI is promising in assessing microstructural changes of EOMs and optic nerves and can help to indicate the disease activity of TAO, especially through the MD of medial EOMs.

Diffusion Tensor Imaging Technology to Quantitatively Assess Abnormal Changes in Patients With Thyroid-Associated Ophthalmopathy

“…In this study, comparing TAO patients with the HC ones, the FA of the EOMs and LG were significantly lower, while the MD were significantly higher. This result was in agreement with the findings of previous studies (Chen H.H. et al, 2020;Chen et al, 2021).…”

“…The interaction between the extraocular muscles and the lacrimal gland in the development of the disease is not obvious. Several previous researches (Lee et al, 2018;Razek et al, 2019;Chen H.H. et al, 2020;Chen et al, 2021) have examined extraocular muscles and lacrimal gland DTI separately, but these studies did not discuss the relevance of orbital soft tissue in the development of the disease.…”

“…DTI has also been widely applied in patients with optic neuritis, glaucoma, and other eye diseases (Kuchling et al, 2017;Colbert et al, 2021). At present, relatively few studies have performed DTI on TAO patients to assess orbital soft tissue microstructural changes (Han et al, 2016;Chen H.H. et al, 2020;Chen et al, 2021).…”

Usefulness of readout-segmented EPI-based diffusion tensor imaging of lacrimal gland for detection and disease staging in thyroid-associated ophthalmopathy

“…A two-way ICC with random rater assumption was used. ICCs < 0.40 represent poor reproducibility, 0.40-0.60 as moderate, 0.61-0.80 as good, and ≥ 0.81 as excellent [26]. Two-sided P values of < 0.05 were considered significant.…”

“…Similar to extraocular muscles, LG was thought to experience an initially acute inflammation characterized by mononuclear cell infiltration, fibroblast proliferation and interstitial edema, and subsequently chronic inactive plateau featured with interstitial fibrosis, and fatty infiltration [26,27]. Considering that diffusivity value, reflecting the magnitude of water diffusion dominated by interstitial space [28], could increase in edematous tissue and decrease in fibrotic and fatty infiltrated tissue [26,29], it is reasonable that the LG of TAO patient, especially that of the active one would present elevated ADC value.…”