Department of Biomedical Engineering, Vanderbilt University, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University, USA.
Department of Pediatrics, Vanderbilt University School of Medicine, USA; Department of Neurology, Vanderbilt University School of Medicine, USA.
Neuroimage. 2018 Nov 15;182:511-521. doi: 10.1016/j.neuroimage.2016.12.067. Epub 2016 Dec 23.
MRI is a valuable tool to assess myelin during development and demyelinating disease processes. While multiexponential T and quantitative magnetization transfer measures correlate with myelin content, neither provides the total myelin volume fraction. In many cases correlative measures are adequate; but to assess microstructure of myelin, (e.g. calculate the g-ratio using MRI), an accurate measure of myelin volume fraction is imperative. Using a volumetric model of white matter, we relate MRI measures of myelin to absolute measures of myelin volume fraction and compare them to quantitative histology. We assess our approach in control mice along with two models of hypomyelination and one model of hypermyelination and find strong agreement between MRI and histology amongst models. This work investigates the sensitivities of MRI myelin measures to changes in axon geometry and displays promise for estimating g-ratio from MRI.
MRI 是评估髓鞘发育和脱髓鞘疾病过程的有价值的工具。虽然多指数 T 和定量磁化传递测量与髓鞘含量相关，但两者都不能提供总髓鞘体积分数。在许多情况下，相关测量是足够的；但是为了评估髓鞘的微观结构（例如，使用 MRI 计算 g 比值），则需要准确测量髓鞘体积分数。使用白质的体积模型，我们将 MRI 测量的髓鞘与髓鞘体积分数的绝对测量值联系起来，并将其与定量组织学进行比较。我们在对照小鼠以及两种低髓鞘模型和一种高髓鞘模型中评估了我们的方法，发现模型之间 MRI 和组织学之间具有很强的一致性。这项工作研究了 MRI 髓鞘测量值对轴突几何形状变化的敏感性，并显示出从 MRI 估计 g 比值的潜力。
