Quantitative Analysis of Inflammation in Orbital Fat of Thyroid-associated Ophthalmopathy Using MRI Signal Intensity

Application of Quantitative MRI in Thyroid Eye Disease: Imaging Techniques and Clinical Practices

Thyroid eye disease (TED) is a complex autoimmune disorder that impairs various orbital structures, leading to cosmetic damage and vision loss. Magnetic resonance imaging (MRI) is a fundamental diagnostic tool utilized in clinical settings of TED, for its accurate demonstration of orbital lesions and indication of disease conditions. The application of quantitative MRI has brought a new prospect to the management and research of TED, offering more detailed information on morphological and functional changes in the orbit. Therefore, many researchers concentrated on the implementation of different quantitative MRI techniques on TED for the exploration of clinical practices. Despite the abundance of studies utilizing quantitative MRI in TED, there remain considerable barriers and disputes on the best exploitation of this tool. This could possibly be attributed to the complexity of TED and the fast development of MRI techniques. It is necessary that clinical and radiological aspects of quantitative MRI in TED be better integrated into comprehensive insights. Hence, this review traces back 30 years of publications regarding quantitative MRI utilized in TED and elucidates this promising application in the facets of imaging techniques and clinical practices. We believe that a deeper understanding of the application of quantitative MRI in TED will enhance the efficacy of the multidisciplinary management of TED. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 3.

Fat-suppression T2 relaxation time and water fraction predict response to intravenous glucocorticoid therapy for thyroid-associated ophthalmopathy

OBJECTIVE

To investigate the value of fat-suppression (FS) T2 relaxation time (T2RT) derived from FS T2 mapping and water fraction (WF) derived from T2 IDEAL to predict the treatment response to intravenous glucocorticoids (IVGC) in patients with thyroid-associated ophthalmopathy (TAO) based on texture analysis.

MATERIALS AND METHODS

In this study, 89 patients clinically diagnosed with active and moderate-to-severe TAO were enroled (responsive group, 48 patients; unresponsive group, 41 patients). The baseline clinical characteristics and texture features were compared between the two groups. Multivariate analysis was performed to identify the independent predictors of treatment response to IVGC. ROC analysis and the DeLong test were used to assess and compare the predictive performance of different models.

RESULTS

The responsive group exhibited significantly shorter disease duration and higher 90th percentile of FS T2RT and kurtosis of WF in the extraocular muscle (EOM) and 95th percentile of WF in the orbital fat (OF) than the unresponsive group. Model 2 (disease duration + WF; AUC, 0.816) and model 3 (disease duration + FS T2RT + WF; AUC, 0.823) demonstrated superior predictive efficacy compared to model 1 (disease duration + FS T2RT; AUC, 0.756), while there was no significant difference between models 2 and 3.

CONCLUSIONS

The orbital tissues of responders exhibited more oedema and heterogeneity. Furthermore, OF is as valuable as EOM for assessing the therapeutic efficacy of IVGC. Finally, WF derived from T2 IDEAL processed by texture analysis can provide valuable information for predicting the treatment response to IVGC in patients with active and moderate-to-severe TAO.

CLINICAL RELEVANCE STATEMENT

The texture features of FS T2RT and WF are different between responders and non-responders, which can be the predictive tool for treatment response to IVGC.

KEY POINTS

Texture analysis can be used for predicting response to IVGC in TAO patients. TAO patients responsive to IVGC show more oedema and heterogeneity in the orbital tissues. WF from T2 IDEAL is a tool to predict the therapeutic response of TAO.

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

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-SIRmax, EOM-SIRmean, EOM-SIRmin, IF-SIRmax, IF-SIRmean, LG-SIRmax, LG-SIRmean, EOM-WFmean, EOM-WFmin, IF-WFmax, IF-WFmean, and LG-WFmean and lower EOM-FFmax, EOM-FFmean, IF-FFmean, IF-FFmin, and LG-FFmean values (all p < 0.05). The EOM-SIRmean, LG-SIRmean, and LG-FFmean values were independently associated with active TAO (all p < 0.05). The combination of the EOM-SIRmean, LG-SIRmean, and LG-FFmean values showed better performance than the EOM-SIRmean 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-SIRmean, LG-SIRmean, and LG-FFmean values were found to independently correlate with active TAO. Joint evaluation of orbital tissue improved the ability to assess TAO activity.

Qualitative and Quantitative Magnetic Resonance Imaging in Bacterial Orbital Cellulitis

PURPOSE

To summarise the qualitative and quantitative parameters of bacterial orbital cellulitis (OC) on magnetic resonance imaging (MRI) and explore their clinical correlations.

METHODS

Multi-centre retrospective study with inclusion of patients of all ages with OC who underwent MRI. Patients with isolated pre-septal cellulitis, bilateral disease and poor-quality scans were excluded. An enlargement ratio for extraocular muscles (EOMs) was calculated by dividing maximal EOM measurements from the affected side by the contralateral side.

RESULTS

Twenty MRI scans from twenty patients (Mean age: 40.8 ± 24.3 years old, M: F = 15:5) between 2011 and 2022 were analysed. Three (15.0%) cases were paediatric patients (<18 years old). All cases had both pre-septal and orbital fat involvement. The EOM were affected in nineteen cases, with the superior muscle complex (18/19, 94.7%) most commonly affected. Mean enlargement ratio (1.30, Range: 1.04-1.82) was greatest for the medial rectus on axial views on T1 and fat-suppressed contrast-enhanced T1 (FS CE T1). Optic peri-neuritis was present in eleven (55.0%) patients, whilst two (9.5%) cases had optic neuritis. A greater degree of proptosis was observed in patients with optic neuropathy and those who underwent surgical intervention compared to those without (p = .002 and p = .002, respectively).

CONCLUSION

MRI remains an important imaging modality for evaluating complicated OC. However, qualitative features may lack accuracy and is not a reproducible means of analysis. Simple quantitative parameters, such as proptosis and EOM measurements, correlate with high-risk clinical features and may have utility in predicting clinical course.

A Randomized Clinical Trial of Intravenous Methylprednisolone With 2 Protocols in Patients With Graves Orbitopathy

CONTEXT

Intravenous glucocorticoid (IVGC) is an accessible and affordable treatment for Graves orbitopathy (GO); the 4.5-g protocol is well studied, but many details of treatment protocols need to be clarified.

OBJECTIVE

To compare the efficacy and safety of weekly and monthly protocol of IVGC in GO.

METHODS

A prospective, randomized, observer-masked, single-center clinical trial, followed up to week 24, at the third affiliated hospital of Southern Medical University; 58 patients with active and moderate to severe GO, aged 18-60 years old, who had not received relevant treatment were included. The intervention was weekly protocol or monthly protocol of IVGC; both received a cumulative dose of methylprednisolone 4.5 g and had a duration of 12 weeks. The overall effective rate, improvement of quality of life (QOL) and signal intensity ratio (SIR) were measured.

RESULTS

There was no significant difference in the effective rate between the 2 groups at week 12 and week 24 (86.21% vs 72.41%, P = .195; 86.21% vs 82.61%, P = .441), there was no significant difference in the improvement of clinical activity score, exophthalmos, soft tissue involvement, diplopia, and QOL. At week 24, the mean SIR and maximum SIR of the 2 groups were lower than those before treatment, and there were no statistically significant difference between the 2 groups. There was no significant difference in the incidence of adverse events between the 2 groups (31.03% vs 27.59%, P = .773).

CONCLUSION

The efficacy and safety of the 2 protocols are comparable; the monthly protocol could be used as an alternative to the weekly protocol.

Magnetic Resonance Imaging in the Management of Thyroid Eye Disease: A Systematic Review

PURPOSE

MRI may potentially detect active thyroid eye disease prior to elevation of clinical activity score. We aimed to systematically review the existing literature pertaining to MRI thyroid eye disease and to assess the role of MRI in the diagnosis of thyroid eye disease.

METHODS

A Population, Intervention, Comparison, Outcome/Preferred Reporting Items for Systematic Reviews and Meta-Analyses selection criteria was applied to identify studies for inclusion published between the years 2000 and 2023.

RESULTS

Twenty-four articles were identified for inclusion in the systematic review. All included studies utilized MRI as the imaging modality. MRI sequences used included T2-weighted imaging in 87.5%, T1-weighted imaging in 54.2%, diffusion-weighted imaging in 20.8%, and short tau inversion recovery in 16.7%. The most common parameters quantified were signal intensity ratio in 10 studies (41.7%) and T2-relaxation time in 8 studies (33.3%). Signal intensity ratio and T2-relaxation time were shown to correlate with clinical activity score and identify the phase of the disease.

CONCLUSIONS

MRI has untapped potential for further elucidating the highly complex biological processes in thyroid eye disease. As we move away from clinical activity score as a predictor of response to biologic therapy, MRI may prove more important than ever in the risk-benefit analysis around the use of immunomodulators.

Application of Multiparameter Quantitative Magnetic Resonance Imaging in the Evaluation of Graves' Ophthalmopathy

BACKGROUND

Assessment of the activity of Graves' ophthalmopathy (GO) is difficult. Existing methods need improvement.

PURPOSE

Investigate the application of multiparametric magnetic resonance imaging (MRI) in GO.

STUDY TYPE

Retrospective.

POPULATION

A total of 235 GO patients (age: 38.8 ± 13.4 years; 90 male; 96 active patients).

FIELD STRENGTH/SEQUENCE

Short-tau inversion recovery (STIR) fast spin echo, multiecho spin echo T2 mapping and 3D T1-weighted fast field echo sequences at 3.0 T.

ASSESSMENT

Two physicians assessed the mean and maximum signal intensity ratio of extraocular muscles to white matter (SIR), T2 relaxation time (T2RT), extraocular muscle area (EMA), fat fraction (FF), retrobulbar fat volume (RFV), and extraocular muscle volume (EMV). Clinical activity score (CAS) ≧ 3 was in active stage.

STATISTICAL TESTS

The optimal cut-off point of diagnostic efficacy was selected using receiver operating characteristic (ROC) curve analysis and evaluated using area under the curve (AUC), compared using Student's t test, analysis of variance or Kruskal-Wallis H test. The correlation used Pearson correlation analysis. The discriminant equation used a binary logistic regression analysis. P < 0.05 was considered statistically significant.

RESULTS

The SIRmean, SIRmax, T2RTmean, T2RTmax, EMA, and EMV in active GO patients were significantly higher than those in inactive and were positively correlated with CAS (r = 0.276, 0.228, 0.438, 0.388, 0.502, and 0333, respectively). The FFmax of active patients was significantly lower than that of inactive patients and was negatively correlated with CAS (r = -0.44). Logistic regression analysis indicated that T2RTmean was independently associated with GO active periods and had good diagnostic performance (area under ROC curve = 0.736, sensitivity 70.7%, specificity 69.3%). T2RTmean ≧ 74.295 could be a diagnostic cut-off for judging GO activity (sensitivity 55.3%).

CONCLUSION

SIR, T2RT, EMV, and FF can quantitatively assess the activity and severity of GO and can potentially provide a basis for clinical judgment and selection of treatment options.

EVIDENCE LEVEL

4.

TECHNICAL EFFICACY

Stage 2.

Efficacy and Safety of 6-Weekly versus 12-Weekly Intravenous Methylprednisolone in Moderate-to-Severe Active Thyroid-Associated Ophthalmopathy

PURPOSE

To compare the efficacy and safety of 6-weekly and 12-weekly intravenous methylprednisolone (IVMP) regimens in moderate-to-severe, active thyroid-associated orbitopathy (TAO) patients.

BASIC PROCEDURES

Retrospective comparative study of patients who received IVMP between January 2011 and July 2021 at the Thyroid Eye Clinic, the Chinese University of Hong Kong. Outcome measures included the 7-item clinical activity score (CAS), exophthalmos, extraocular muscle motility (EOMy), marginal reflex distance (MRD), best corrected visual acuity (BCVA), intraocular pressure (IOP), the requirement of additional treatment, and complications.

MAIN FINDINGS

A total of 65 (63% (41/65) females) moderate-to-severe, active TAO patients aged 50 ± 13 (25-74) years received 6-weekly (n = 22) or 12-weekly (n = 43) IVMP. Sex, age, smoking status, and Graves' disease status were comparable in the two groups (all p > 0.05). CAS at week 6 (p = 0.0279), 12 (p = 0.00228), and 52 (p = 0.0228) were lower at each time for the 12-weekly group. Exophthalmos improved more at week 6 (p = 0.0453) and 12 (p = 0.0347) in the 12-weekly group. The improvement of diplopia, MRD1, MRD2, and EOMy were comparable between the two groups. More patients in the 6-weekly group (p = 0.00169) required additional treatments including IVMP+/-ORT. Patients in the 6-weekly group who did not require additional treatment had a lower presenting CAS (p = 0.0193) than those who required additional treatment. The total numbers of adverse events were comparable between the two groups.

Research progress and application of artificial intelligence in thyroid associated ophthalmopathy

Thyroid-associated ophthalmopathy (TAO) is a complicated orbitopathy related to dysthyroid, which severely destroys the facial appearance and life quality without medical interference. The diagnosis and management of thyroid-associated ophthalmopathy are extremely intricate, as the number of professional ophthalmologists is limited and inadequate compared with the number of patients. Nowadays, medical applications based on artificial intelligence (AI) algorithms have been developed, which have proved effective in screening many chronic eye diseases. The advanced characteristics of automated artificial intelligence devices, such as rapidity, portability, and multi-platform compatibility, have led to significant progress in the early diagnosis and elaborate evaluation of these diseases in clinic. This study aimed to provide an overview of recent artificial intelligence applications in clinical diagnosis, activity and severity grading, and prediction of therapeutic outcomes in thyroid-associated ophthalmopathy. It also discussed the current challenges and future prospects of the development of artificial intelligence applications in treating thyroid-associated ophthalmopathy.

Graves' Eye Disease: Clinical and Radiological Diagnosis

Graves' disease is an autoimmune disorder in which hyperthyroidism results in various systematic symptoms, with about 30% of patients presenting with Graves' eye disease (GED). The majority of patients with GED develop mild symptoms, including eyelid retraction, exposure of the globe, superior rectus-levator muscle complex inflammation, and fat expansion, leading to exophthalmos. More severe cases can result in extraocular muscle enlargement, restricted ocular movement, eyelid and conjunctival edema, and compression of the optic nerve leading to compressive optic neuropathy (CON). GED severity can be classified using the Clinical Activity Score, European Group on Graves' Orbitopathy scale, NO SPECS Classification system, and VISA system. CT and MRI aid in the diagnosis of GED through the demonstration of orbital pathology. Several recent studies have shown that MRI findings correlate with disease severity and can be used to evaluate CON. Mild cases of GED can be self-limiting, and patients often recover spontaneously within 2-5 years. When medical treatment is required, immunomodulators or radiotherapy can be used to limit immunologic damage. Surgery may be needed to improve patient comfort, preserve the orbit, and prevent vision loss from optic nerve compression or breakdown of the cornea.

MRI in the assessment of thyroid-associated orbitopathy activity

Management of patients with thyroid-associated orbitopathy (also called Graves' disease) is dependent on the assessment of the disease activity. Evaluation of disease activity is based on ophthalmological examination. Magnetic resonance imaging (MRI) is an auxiliary method that may help quantify the activity and is also helpful in obtaining anatomical information concerning muscle thickness, exophthalmos, or optic neuropathy. We present a review of MRI techniques of the orbits with emphasis on the evaluation of disease activity. The most convincing seems to be the group of T2-weighted techniques such as conventional T2 weighting, T2 relaxometry, and T2 mapping. Dynamic contrast-enhanced MRI is another promising method.

TSAb/TRAb ratio as a sensitive screening test for active Graves' orbitopathy

OBJECTIVE

Graves' orbitopathy (GO), an extrathyroidal manifestation of Graves' disease, can seriously threaten the patient's quality of life. Given that immunosuppressive treatment during the early active phase of GO has been found to reduce both disease activity and severity, sensitive screening tests are needed.

METHODS

The present study included 86 patients with GO, in whom serum levels of thyroid-stimulating hormone (TSH), free T3, free T4, thyroid-stimulating antibody, TSH receptor antibody, thyroid peroxidase antibody, thyroglobulin, and thyroglobulin antibody were measured within 2 months before magnetic resonance imaging (MRI)for orbit assessment.

RESULTS

The thyroid-stimulating antibody/TSH receptor antibody ratio was able to distinguish MRI results with a correct classification rate of 81%. When focusing on patients without T3 predominant Graves' diseases, the ratio distinguished MRI results at a rate of 92%. Receiver operating characteristic curve analysis revealed a cutoff antibody ratio of 87, which yielded a sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of 91%, 95%, 18.2, and 0.0957, respectively, for distinguished MRI results.

CONCLUSIONS

The thyroid-stimulating antibody/TSH receptor antibody ratio is a highly sensitive and specific indicator for active GO, especially in patients without T3 predominance, and serves as a good screening test for active GO in primary care settings.

Extraocular muscle enlargement

Extraocular muscle enlargement can occur secondary to a range of orbital and systemic diseases. Although the most common cause of extraocular muscle enlargement is thyroid eye disease, a range of other inflammatory, infective, neoplastic, and vascular conditions can alter the size and shape of the extraocular muscles. Imaging with computed tomography and magnetic resonance imaging plays an essential role in the workup of these conditions. This article provides an image-rich review of the wide range of pathology that can cause enlargement of the extraocular muscles.

Effect of systemic steroid therapy in Graves' orbitopathy on regulatory T cells and Th17/Treg ratio

PURPOSE

Glucocorticoids are a mainstay treatment for Graves' orbitopathy, yet their exact mechanisms of action remain unclear. We aimed to determine whether the therapeutic effects of systemic steroid therapy in Graves' orbitopathy are mediated by changes in regulatory T lymphocytes (Tregs) and T helper 17 lymphocytes (Th17).

METHODS

We assessed Treg and Th17 levels in the peripheral blood of 32 patients with active, moderate-to-severe Graves' orbitopathy who received 12 weekly pulses of methylprednisolone, and determined their association with disease severity, disease activity, and treatment outcomes. The acute orbitopathy phase was confirmed based on clinical evaluation and magnetic resonance imaging, and assessed using the clinical activity score (CAS). The severity of the disease was classified according to ETA/EUGOGO guidelines, and quantified based on the total eye score. Treatment response was determined based on specific criteria (e.g., changes in CAS score, diplopia grade, visual acuity, etc.). Treg and Th17 cells were identified using flow cytometry.

RESULTS

Methylprednisolone treatment improved the activity of the disease and altered the Th17/Treg balance (i.e., the percentage of Tregs decreased while the number of Th17 cells remained unchanged). There was no association between the Treg/Th17 ratio and the activity and severity of the disease or the treatment response.

CONCLUSIONS

Therapeutic effects of steroid therapy in Graves' orbitopathy are not mediated by Treg and Th17 alterations in the peripheral blood. The decrease in peripheral Treg percentage is likely a consequence of the non-specific effects of steroids and does not impact clinical outcome.

Extrathyroidal Manifestations of Thyroid Disease: Graves Eye Disease

Graves disease is an autoimmune disorder caused by the breakdown of immune tolerance to thyroid antigens against the TSH receptor. In approximately 25% of patients, an inflammatory condition, Graves eye disease (GED), affects the orbital soft tissues. About 60% of patients develop mild symptoms including fat expansion and inflammation of the levator muscle complex with resultant proptosis, eyelid retraction, and exposure of the globe. The remaining patients experience enlargement of one or more of the extraocular muscles, leading to conjunctival and eyelid edema and congestion, restricted ocular movement with resultant diplopia, and optic nerve compression leading to compressive optic neuropathy.

Advances in magnetic resonance imaging of orbital disease

Magnetic resonance imaging (MRI) is increasingly used by the orbital surgeon to aid in the diagnosis, surgical planning, and monitoring of orbital disease. MRI provides superior soft tissue detail compared with computed tomography or ultrasound, and advancing techniques enhance its ability to highlight abnormal orbital pathology. Diffusion-weighted imaging is a specialized technique that uses water molecule diffusion patterns in tissue to generate contrast signals and can help distinguish malignant from benign lesions. Steady-state free precession sequences such as Constructive Interference in Steady-State (CISS) and Fast Imaging Employing Steady-state Acquisition (FIESTA) generate highly detailed, 3-dimensional reconstructed images and are particularly useful in distinguishing structures adjacent to cerebral spinal fluid. Magnetic resonance angiography can be used to characterize vascular lesions within the orbit. New developments in magnetic field strength as well as the use of orbital surface coils achieve increasingly improved imaging resolution.

Detection of active and inactive phases of thyroid-associated ophthalmopathy using deep convolutional neural network

Background

This study aimed to establish a deep learning system for detecting the active and inactive phases of thyroid-associated ophthalmopathy (TAO) using magnetic resonance imaging (MRI). This system could provide faster, more accurate, and more objective assessments across populations.

Methods

A total of 160 MRI images of patients with TAO, who visited the Ophthalmology Clinic of the Ninth People’s Hospital, were retrospectively obtained for this study. Of these, 80% were used for training and validation, and 20% were used for testing. The deep learning system, based on deep convolutional neural network, was established to distinguish patients with active phase from those with inactive phase. The accuracy, precision, sensitivity, specificity, F1 score and area under the receiver operating characteristic curve were analyzed. Besides, visualization method was applied to explain the operation of the networks.

Results

Network A inherited from Visual Geometry Group network. The accuracy, specificity and sensitivity were 0.863±0.055, 0.896±0.042 and 0.750±0.136 respectively. Due to the recurring phenomenon of vanishing gradient during the training process of network A, we added parts of Residual Neural Network to build network B. After modification, network B improved the sensitivity (0.821±0.021) while maintaining a good accuracy (0.855±0.018) and a good specificity (0.865±0.021).

Conclusions

The deep convolutional neural network could automatically detect the activity of TAO from MRI images with strong robustness, less subjective judgment, and less measurement error. This system could standardize the diagnostic process and speed up the treatment decision making for TAO.

Dixon-T2WI magnetic resonance imaging at 3 tesla outperforms conventional imaging for thyroid eye disease

OBJECTIVES

To determine the diagnostic performances of a single Dixon-T2-weighted imaging (WI) sequence compared to a conventional protocol including T1-, T2-, and fat-suppressed T2-weighted MRI at 3 T when assessing thyroid eye disease (TED).

MATERIALS AND METHODS

This IRB-approved prospective single-center study enrolled participants presenting with confirmed TED from April 2015 to October 2019. They underwent an MRI, including a conventional protocol and a Dixon-T2WI sequence. Two neuroradiologists, blinded to all data, read both datasets independently and randomly. They assessed the presence of extraocular muscle (EOM) inflammation, enlargement, fatty degeneration, or fibrosis as well as the presence of artifacts. The Wilcoxon signed-rank test was used.

RESULTS

Two hundred six participants were enrolled (135/206 [66%] women, 71/206 [34%] men, age 52.3 ± 13.2 years). Dixon-T2WI was significantly more likely to detect at least one inflamed EOM as compared to the conventional set (248/412 [60%] versus 228/412 [55%] eyes; (p = 0.02). Dixon-T2WI was more sensitive and specific than the conventional set for assessing muscular inflammation (100% versus 94.7% and 71.2% versus 68.5%, respectively). Dixon-T2WI was significantly less likely to show major or minor artifacts as compared to fat-suppressed T2WI (20/412 [5%] versus 109/412 [27%] eyes, p < 0.001, and 175/412 [42%] versus 257/412 [62%] eyes, p < 0.001). Confidence was significantly higher with Dixon-T2WI than with the conventional set (2.35 versus 2.24, p = 0.003).

CONCLUSION

Dixon-T2WI showed higher sensitivity and specificity and showed fewer artifacts than a conventional protocol when assessing thyroid eye disease, in addition to higher self-reported confidence.

KEY POINTS

• Dixon-T2WI has better sensitivity and specificity than a conventional protocol for assessing inflamed extraocular muscles in patients with thyroid eye disease. • Dixon-T2WI shows significantly fewer artifacts than fat-suppressed T2WI. • Dixon-T2WI is faster and is associated with significantly higher self-reported reader confidence as compared to a conventional protocol when assessing inflammatory extraocular muscles.

The feasibility of quantitative MRI of extra-ocular muscles in myasthenia gravis and Graves' orbitopathy

Although quantitative MRI can be instrumental in the diagnosis and assessment of disease progression in orbital diseases involving the extra-ocular muscles (EOM), acquisition can be challenging as EOM are small and prone to eye-motion artefacts. We explored the feasibility of assessing fat fractions (FF), muscle volumes and water T2 (T2_water ) of EOM in healthy controls (HC), myasthenia gravis (MG) and Graves' orbitopathy (GO) patients. FF, EOM volumes and T2_water values were determined in 12 HC (aged 22-65 years), 11 MG (aged 28-71 years) and six GO (aged 28-64 years) patients at 7 T using Dixon and multi-echo spin-echo sequences. The EOM were semi-automatically 3D-segmented by two independent observers. MANOVA and t-tests were used to assess differences in FF, T2_water and volume of EOM between groups (P < .05). Bland-Altman limits of agreement (LoA) were used to assess the reproducibility of segmentations and Dixon scans. The scans were well tolerated by all subjects. The bias in FF between the repeated Dixon scans was -0.7% (LoA: ±2.1%) for the different observers; the bias in FF was -0.3% (LoA: ±2.8%) and 0.03 cm³ (LoA: ± 0.36 cm³ ) for volume. Mean FF of EOM in MG (14.1% ± 1.6%) was higher than in HC (10.4% ± 2.5%). Mean muscle volume was higher in both GO (1.2 ± 0.4 cm³ ) and MG (0.8 ± 0.2 cm³ ) compared with HC (0.6 ± 0.2 cm³ ). The average T2_water for all EOM was 24.6 ± 4.0 ms for HC, 24.0 ± 4.7 ms for MG patients and 27.4 ± 4.2 ms for the GO patient. Quantitative MRI at 7 T is feasible for measuring FF and muscle volumes of EOM in HC, MG and GO patients. The measured T2_water was on average comparable with skeletal muscle, although with higher variation between subjects. The increased FF in the EOM in MG patients suggests that EOM involvement in MG is accompanied by fat replacement. The unexpected EOM volume increase in MG may provide novel insights into underlying pathophysiological processes.

Teprotumumab reduces extraocular muscle and orbital fat volume in thyroid eye disease

Purpose

Thyroid eye disease (TED) is a progressive, debilitating and potentially vision-threatening autoimmune disease. Teprotumumab, a novel human monoclonal antibody, has been shown to reverse the clinical manifestations of TED. Patients receiving teprotumumab have been shown in two multicenter, randomized placebo-controlled trials to have decreased proptosis, diplopia and inflammation after 24 weeks of treatment. This study aims to analyse volumetric and inflammatory changes on orbital imaging prior to and after teprotumumab treatment from one of these trials.

Design

Retrospective review.

Subjects

Six patients enrolled in the phase III teprotumumab clinical trial (OPTIC, NCT03298867) with active TED who received 24 weeks of teprotumumab and had pre- and post-treatment orbital imaging (CT or MRI). Additionally, 12 non-TED patients (24 orbits) were analysed as a comparative control group.

Methods

3D volumetric calculations of the extraocular muscles (EOMs), orbital fat, and bony orbit were measured using previously validated image processing software. 3D volumetric results and changes in EOM inflammation were compared with clinical measurements of TED.

Results

Total EOM volume within each orbit was markedly reduced post-teprotumumab in all patients (n=six patients, 12/12 orbits, p<0.02). There was no statistical difference in post-treatment EOM volume when compared to non-TED controls. Total orbital fat volume was also reduced in 11 of 12 studied orbits (n=six patients, p=0.04). Overall EOM inflammation based on MRI signal intensity ratio was reduced in 8/8 orbits (n=four patients, p<0.01).

Conclusion

Orbital imaging demonstrated decreased EOM volumes and orbital fat tissue volumes after teprotumumab treatment.

Predicting the response to glucocorticoid therapy in thyroid-associated ophthalmopathy: mobilizing structural MRI-based quantitative measurements of orbital tissues

PURPOSE

We aimed to evaluate the performance of structural magnetic resonance imaging (MRI)-based quantitative measurements at extraocular muscle (EOM), orbital fat (OF), and especially lacrimal gland (LG) in predicting response to glucocorticoid (GC) in patients with active and moderate-severe thyroid-associated ophthalmopathy (TAO).

METHODS

Forty-seven active and moderate-severe TAOs (responsive group, 29 patients and 58 eyes; unresponsive group, 18 patients and 36 eyes) were enrolled. Pretreatment MRI-based parameters of EOM, OF, and LG, and clinical factors were retrospectively collected and compared between two groups. Logistic regression and receiver operating characteristic curve analyses were used to assess the predictive value of identified independent variables.

RESULTS

Responsive group showed significantly higher minimum signal intensity ratio of EOM (EOM-SIR_min) (p < 0.001), higher EOM-SIR_mean (p = 0.034), higher LG herniation (LGH) (p = 0.019), lower OF thickness (OFT) (p = 0.017), higher LGH/OFT ratio (p = 0.001), and shorter disease duration (p = 0.004) than unresponsive group. Multivariate analysis showed that EOM-SIR_min, LGH/OFT ratio, and disease duration were independent predictors for responsive TAOs (all p < 0.05). Integration of three independent predictors demonstrated optimal predictive efficiency (area under curve, 0.829). Combining EOM-SIR_min ≥1.43 and LGH/OFT ratio ≥1.65, optimal predictive specificity (94.4%) could be obtained, while optimal predictive sensitivity (82.8%) was achieved when integrating disease duration ≤3.5 and LGH/OFT ratio ≥1.65.

CONCLUSIONS

Structural MRI-based quantitative measurements at EOM, OF, and LG, specially EOM-SIR_min and LGH/OFT ratio, together with disease duration, may serve as promising markers to predict response to GC in patients with active and moderate-severe TAO.

Low signal intensities of MRI T1 mapping predict refractory diplopia in Graves' ophthalmopathy

OBJECTIVE

In Graves' ophthalmopathy (GO), fibrosis in extraocular muscles (EOMs) may be related to intravenous glucocorticoid (ivGC)-resistant diplopia. Signal intensity (SI) of magnetic resonance imaging (MRI) T1 mapping can quantify properties of EOM components, including fibrosis. We investigated EOM features of GO patients with diplopia using T1 mapping SI and the predictive value of T1 mapping SI in the response of diplopia to ivGCs.

DESIGN

We performed a cross-sectional study that included 13 active GO patients, 34 inactive GO patients with history of diplopia, including 20 with a history of diplopia disappearance, 14 GO patients with refractory diplopia and 35 control subjects. In nine active GO patients, the relationship between T1 mapping SI at pretreatment and at diplopia outcome after ivGC treatment was prospectively investigated.

METHODS

T1 mapping SI of left and right inferior rectus and medial rectus muscles was measured in all participants.

RESULTS

T1 mapping SI in inactive GO patients with refractory diplopia was significantly lower than that of other groups in all evaluated EOMs. Diagnostic accuracy for refractory diplopia by T1 mapping SI in GO patients with a history of diplopia disappearance was excellent (AUC 0.89) compared with other assessments. Furthermore, among nine active GO patients, pretreatment T1 mapping SI in four patients with ivGC-resistant diplopia tended to be low compared with the other five patients with improved diplopia.

CONCLUSIONS

Low intensity T1 mapping in EOMs is likely to be associated with refractory diplopia and may be useful in predicting the response of diplopia to ivGCs.

A quantitative method to assess muscle edema using short TI inversion recovery MRI

Muscle inflammation is an important component of disease pathophysiology in several muscular dystrophies. Hyperintensities on MRI sequences with short TI inversion recovery (STIR) reflect edema, or inflammation (STIR+). Conventionally, STIR evaluation has been done by visual inspection. In this study, we developed a quantitative STIR method, and tested its ability to identify STIR+ lesions in healthy controls and patients with Facioscapulohumeral muscular dystrophy and compared the results with visual STIR evaluation and quantitative T2 relaxation time mapping. The method was based on pixel-by-pixel histograms of the distribution of signal intensities from muscles. Signal intensities from healthy control muscles were averaged and used to define an upper reference limit. Muscles with >2.5% pixels above the limit were defined as being STIR+. The new method showed agreement with T2 relaxation time mapping in 95% of muscles. The visual STIR method only showed agreement with the quantitative STIR method and T2 relaxation time mapping in 88 and 84%, respectively. STIR sequences are available on most MR scanners and the post-processing used in the new quantitative method can be performed using free software. We therefore believe that the new method can play an important role in identifying STIR+ lesions in patients with neuromuscular diseases.

Radiological Staging of Thyroid-Associated Ophthalmopathy: Comparison of T1 Mapping with Conventional MRI

BACKGROUND

Accurate staging of patients with thyroid-associated ophthalmopathy (TAO) is crucial for clinical decision. Full cognition of pathologic changes and staging TAO using conventional T2-weighted imaging is still limited.

PURPOSE

To investigate the feasibility of using T1 mapping to evaluate changes of extraocular muscles (EOMs) in TAO patients, as well as to compare T1 mapping and conventional T2-weighted imaging in staging TAO.

MATERIALS AND METHODS

Forty TAO patients were retrospectively enrolled. "Hot spot" and "cold spot" T1 relaxation times (T1RT_HS and T1RT_CS) of EOMs, as well as conventionally applied highest signal intensity ratio (SIR) of EOMs, were measured and compared between active and inactive groups.

RESULTS

T1RT_CS and SIR were significantly higher in active TAOs than in the inactive ones (P < 0.001), while T1RT_HS was not (P=0.093). Meanwhile, T1RT_CS and SIR were positively correlated with clinical activity score (r = 0.489, 0.540; P < 0.001). TIRT_CS and SIR showed no significant area under curve for staging TAO (0.830 vs. 0.852; P=0.748). T1RT_CS ≥ 1000 alone showed optimal staging specificity (90.0%), while integration of T1RT_CS ≥ 1000 and SIR ≥ 2.9 demonstrated optimal staging efficiency and sensitivity (area under curve, 0.900; sensitivity, 86.0%).

CONCLUSIONS

Our findings suggest that the T1-mapping technique holds the potency to be utilized in TAO. The derived T1RT_CS of EOMs, which may be associated with fat infiltration, could be a useful biomarker to stage the disease, serving added efficiency, sensitivity, and specificity to single usage of conventional SIR.

Treatment with bimatoprost for exophthalmos in patients with inactive thyroid-associated ophthalmopathy

Purpose

This study was performed to observe changes prospectively in exophthalmos and orbital fat in patients with inactive thyroid-associated ophthalmopathy (TAO) treated with bimatoprost.

Methods

In this 12-month single-treatment pilot observational study, 13 patients with inactive-phase TAO were administered bimatoprost to treat exophthalmos due to TAO. Exophthalmos values and orbital tissue volumes were measured on MRI by technicians in a masked fashion.

Results

Nine orbits of nine patients (eight women, one man) were treated with bimatoprost for 12 months. Mean exophthalmos values before and after treatment were 21.7±2.2 and 21.7±2.0 mm, respectively. The mean value after 12 months of treatment was not significantly different from before treatment (P=0.82). Mean orbital fat volume before and after 12 months of treatment was 17.2±2.5 and 17.0±3.0 cm³, respectively. The corresponding total extraocular muscle volume was 4.0±0.7 and 3.8±0.9 cm³, respectively. Mean volume in each tissue type after 12 months of treatment was not significantly different from before treatment (orbital fat, P=0.70; extraocular muscles, P=0.32).

Conclusion

Topical bimatoprost treatment did not reduce exophthalmos or orbital fat in this cohort of patients with inactive TAO.

Management of graves myopathy: Orbital imaging in thyroid-related orbitopathy

A broad understanding of the different imaging modalities used to assess the physiologic changes seen in Graves' orbitopathy complement clinical examination. Subtle applications of radiographic imaging techniques allow for a better understanding of the overall physiology of the orbit, quantify progression of disease, and differentiate it from orbital diseases with overlapping features. A nuanced approach to interpreting imaging features may allow us to delineate inactive from active thyroid eye disease, and advances within this field may arm clinicians with the ability to better predict and prevent dysthyroid optic neuropathy.