Objective Inflammation in patients with myositis would increase diffusion of water molecules across sarcolemma that could be detected with the help of diffusion tensor imaging (DTI). We aimed to determine an association between DTI of vastus lateralis (VL) and histopathological findings in cases of myositis and to estimate diagnostic performance of different MRI variables in predicting histopathological outcomes. Methods This prospective cross-sectional observational study included 43 patients with myositis. MRI of bilateral thighs with DWI/DTI protocol was performed in all the patients. Thirty-three patients further underwent biopsy of right VL muscle. Imaging analysis included grading of “Muscle oedema” based on signal intensity (SI) and extent and “fatty infiltration” based on extent on conventional sequences and, acquiring DWI and DTI parameters. Gold standard method to determine inflammation in muscles was histopathological examination. Comparison of DTI/DWI variables with clinical and histopathological variables was done. Results The average DWI apparent diffusion coefficient (ADC) and DTI ADC values in the patients were 1.77 ± 0.35 and 2.06 ± 0.35 respectively. The average functional anisotropy (FA) was 0.39 ± 0.17 and, the 3 eigenvalues in the patients were 2.96 ± 0.63, 2.05 ± 0.32, and 1.20 ± 0.39 respectively. VL oedema SI weighted score was the best parameter for predicting effaced fascicular architecture and marked lymphocytic inflammation in endomysium on histopathology. VL fatty infiltration weighted score was the best parameter in predicting perifascicular atrophy. Conclusion Addition of DWI or DTI didn’t add significantly in determining active inflammation in cases of myositis.

中文翻译：

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炎性肌病患者股外侧肌的弥散张量成像


目的 肌炎患者的炎症会增加水分子在肌膜上的扩散，这可以通过弥散张量成像 （DTI） 检测到。我们旨在确定股外侧肌 （VL） 的 DTI 与肌炎病例的组织病理学发现之间的关联，并估计不同 MRI 变量在预测组织病理学结果方面的诊断性能。方法 这项前瞻性横断面观察研究包括 43 例肌炎患者。对所有患者进行 DWI/DTI 方案的双侧大腿 MRI。33 例患者进一步接受了右侧 VL 肌活检。影像学分析包括根据信号强度 （SI） 和范围对“肌肉水肿”进行分级，根据常规序列的程度对“脂肪浸润”进行分级，并获取 DWI 和 DTI 参数。确定肌肉炎症的金标准方法是组织病理学检查。将 DTI/DWI 变量与临床和组织病理学变量进行比较。结果 患者平均 DWI 表观弥散系数 （ADC） 和 DTI ADC 值分别为 1.77 ± 0.35 和 2.06 ± 0.35。平均功能各向异性 （FA） 分别为 0.39 ± 0.17，患者的 3 个特征值分别为 2.96 ± 0.63、2.05 ± 0.32 和 1.20 ± 0.39。VL 水肿 SI 加权评分是预测组织病理学上肌内膜消失束结构和显著淋巴细胞炎症的最佳参数。VL 脂肪浸润加权评分是预测束周围萎缩的最佳参数。结论 在肌炎病例中，添加 DWI 或 DTI 在确定活动性炎症方面没有显着增加。