Centre for Medical Imaging, University College London, London, United Kingdom.
Department of Medical Physics, University College London Hospitals, London, United Kingdom.
NMR Biomed. 2020 Nov;33(11):e4390. doi: 10.1002/nbm.4390. Epub 2020 Aug 4.
Diffusion-weighted imaging has received attention as a method for characterizing inflammatory exudates in bone marrow in immune-mediated inflammatory diseases and reveals an increase in diffusivity in regions of bone marrow oedema. Various models of diffusion attenuation have been investigated but the model providing the best description of tissue pathophysiology in regions of marrow oedema is unknown. Determining the most appropriate model is an important step towards protocol optimization and the development of a robust and clinically useful method. We aimed to determine which of three candidate models of diffusion attenuation most accurately describes the acquired signal from normal and inflamed bone marrow. 11 subjects with spondyloarthritis and evidence of active inflammation (ie bone marrow oedema) on MRI and 17 patients with no evidence of active inflammation underwent diffusion-weighted imaging of the sacroiliac joints (b-values 0, 50, 100, 300 and 600 s/mm ). Monoexponential, intravoxel incoherent motion (IVIM) and kurtosis models were fitted to the acquired signal from regions of interest in areas of bone marrow oedema and normal marrow. The three models were compared in terms of sum of squared error and information content (corrected Akaike information criterion). Model parameters were compared between regions of bone marrow oedema and regions of normal marrow. f the three models investigated, the IVIM model provided the best description of the signal over the 0-600 s/mm range across normal and inflamed bone marrow. There was a particular advantage of the IVIM model in normal marrow, where it was best able to capture the pronounced fast diffusion component observed in several cases. However, IVIM and kurtosis effects both became smaller and the signal behaviour became closer to monoexponential in the presence of bone marrow oedema. Our data suggest that increases in D (in the IVIM framework) might account for the reduced deviation from monoexponential behaviour in oedematous bone.
扩散加权成像作为一种在免疫介导的炎症性疾病中对骨髓炎症渗出物进行特征描述的方法已受到关注，它揭示了骨髓水肿区域扩散率的增加。已经研究了各种扩散衰减模型，但尚不清楚哪种模型能最好地描述骨髓水肿区域的组织病理生理学。确定最合适的模型是优化方案和开发稳健且具有临床应用价值的方法的重要步骤。我们旨在确定三种候选扩散衰减模型中哪一种最能准确描述正常和炎症性骨髓的获得信号。11 名患有脊柱关节炎且 MRI 显示有活动性炎症（即骨髓水肿）的患者和 17 名无活动性炎症的患者接受了骶髂关节的扩散加权成像（b 值为 0、50、100、300 和 600 s/mm）。单指数、体素内不相干运动（IVIM）和峰度模型被拟合到骨髓水肿区域和正常骨髓区域的感兴趣区域的获得信号。根据均方误差和信息量（校正的 Akaike 信息准则）比较了这三种模型。比较了骨髓水肿区域和正常骨髓区域的模型参数。在所研究的三种模型中，IVIM 模型在正常和炎症性骨髓的 0-600 s/mm 范围内提供了对信号的最佳描述。在正常骨髓中，IVIM 模型具有特别的优势，它能够最好地捕捉到几个病例中观察到的明显快速扩散成分。然而，在存在骨髓水肿的情况下，IVIM 和峰度效应都变小，信号行为变得更接近单指数。我们的数据表明，在 IVIM 框架中，D 的增加可能解释了水肿性骨髓中从单指数行为的偏差减小。
