PURPOSE We aimed to investigate the performance of T1 mapping and its histological correlation with extraocular muscle fibrosis in thyroid-associated ophthalmopathy (TAO). METHODS We prospectively recruited 12 cases of active TAO, 12 cases of inactive TAO, and 15 cases of control subjects. All participants underwent magnetic resonance imaging (MRI) scan with pre-/postcontrast T1 mapping and short-time inversion-recovery (STIR) sequence. The images were analyzed to obtain precontrast T1, extracellular-volume (ECV) fraction on T1 mapping, and signal-intensity ratio (SIR) on STIR for each rectus. Muscle biopsy was performed at lateral rectus to quantify-collagen volume fraction, glycosaminoglycan (GAG)-volume fraction, and extracellular space component. The relationship between MRI and histopathology was examined with Pearson correlation coefficient. RESULTS The active TAO group was characterized with GAG accumulation, while the inactive TAO group presented with substantial fibrosis. The MRI parameters achieved acceptable interobserver and intraobserver agreement. The precontrast T1 and ECV remarkably increased in the TAO groups than the control group, and ECV positively correlated with collagen-volume fraction (r = 0.913) and extracellular-space component (r = 0.886) in the inactive TAO group. The SIR statistically increased in the active TAO group, and SIR positively correlated with GAG-volume fraction in all three groups. The performance of ECV (cutoff > 48.1%) to screen out extraocular muscle fibrosis in inactive TAO was 60.9% sensitivity and 93.3% specificity. CONCLUSIONS The ECV parameter on T1 mapping MRI is a reliable tool to quantify extraocular muscle fibrosis, providing insights into noninvasive evaluation of pathological changes in TAO orbit. TRIAL REGISTRATION NUMBER ChiCTR2000040394; Date of registration: 28 November 2020.

中文翻译：

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定量 T1 映射 MRI 用于评估甲状腺相关眼病中的眼外肌纤维化。

目的 我们旨在研究甲状腺相关性眼病 (TAO) 中 T1 映射的性能及其与眼外肌纤维化的组织学相关性。方法 我们前瞻性地招募了 12 例活动性 TAO、12 例非活动性 TAO 和 15 例对照受试者。所有参与者都接受了磁共振成像 (MRI) 扫描，包括增强前/增强后 T1 映射和短时反转恢复 (STIR) 序列。分析图像以获得每个直肌的增强前 T1、T1 映射上的细胞外体积 (ECV) 分数和 STIR 上的信号强度比 (SIR)。在外直肌进行肌肉活检以量化胶原体积分数、糖胺聚糖 (GAG) 体积分数和细胞外空间成分。用皮尔逊相关系数检查MRI与组织病理学之间的关系。结果活性TAO组以GAG积累为特征，而非活性TAO组表现为大量纤维化。MRI 参数达到了可接受的观察者间和观察者内一致性。TAO组的增强前T1和ECV显着高于对照组，并且ECV与非活性TAO组的胶原体积分数（r = 0.913）和细胞外空间成分（r = 0.886）呈正相关。活性 TAO 组的 SIR 在统计学上增加，并且在所有三组中 SIR 与 GAG 体积分数呈正相关。ECV（截止值 > 48.1%）在非活动性 TAO 中筛查眼外肌纤维化的敏感性为 60.9%，特异性为 93.3%。结论 T1 映射 MRI 上的 ECV 参数是量化眼外肌纤维化的可靠工具，提供对 TAO 轨道病理变化的无创评估的见解。试用注册号 ChiCTR2000040394；注册日期：2020 年 11 月 28 日。