使用高梯度弥散 MRI 和大分子组织容积成像技术评估多发性硬化症的 G 比值

Imaging G-Ratio in Multiple Sclerosis Using High-Gradient Diffusion MRI and Macromolecular Tissue Volume.

机构信息

From the Division of Neuroradiology (F.Y.), Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas

Athinoula A. Martinos Center for Biomedical Imaging (Q.F., Q.T., C.N., A.N., T.W., L.L.W., S.Y.H.), Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts.

出版信息

AJNR Am J Neuroradiol. 2019 Nov;40(11):1871-1877. doi: 10.3174/ajnr.A6283. Epub 2019 Nov 6.

DOI:10.3174/ajnr.A6283

PMID:31694819

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC6975105/

Abstract

BACKGROUND AND PURPOSE

Remyelination represents an area of great therapeutic interest in multiple sclerosis but currently lacks a robust imaging marker. The purpose of this study was to use high-gradient diffusion MRI and macromolecular tissue volume imaging to obtain estimates of axonal volume fraction, myelin volume fraction, and the imaging g-ratio in patients with MS and healthy controls and to explore their relationship to neurologic disability in MS.

MATERIALS AND METHODS

Thirty individuals with MS (23 relapsing-remitting MS, 7 progressive MS) and 19 age-matched healthy controls were scanned on a 3T MRI scanner equipped with 300 mT/m maximum gradient strength using a comprehensive multishell diffusion MRI protocol. Macromolecular tissue volume imaging was performed to quantify the myelin volume fraction. Diffusion data were fitted to a 3-compartment model of white matter using a spheric mean approach to yield estimates of axonal volume fraction. The imaging g-ratio was calculated from the ratio of myelin volume fraction and axonal volume fraction. Imaging metrics were compared between groups using 2-sided tests with a Bonferroni correction.

RESULTS

The mean g-ratio was significantly elevated in lesions compared with normal-appearing WM (0.74 vs 0.67, < .001). Axonal volume fraction (0.17 vs 0.23, < .001) and myelin volume fraction (0.17 vs 0.25, < .001) were significantly lower in lesions than normal-appearing WM. Myelin volume fraction was lower in normal-appearing WM compared with that in healthy controls (0.25 vs 0.27, = .009). Disability, as measured by the Expanded Disability Status Scale, was significantly associated with myelin volume fraction (β = -40.5, = .001) and axonal volume fraction (β = -41.0, = .016) in normal-appearing WM.

CONCLUSIONS

The imaging g-ratio may serve as a biomarker for the relative degree of axonal and myelin loss in MS.

摘要

背景与目的

髓鞘再生是多发性硬化症（MS）治疗领域的一个热点，但目前缺乏一种可靠的影像学标志物。本研究旨在使用高梯度弥散 MRI 和大分子组织容积成像来评估 MS 患者和健康对照者的轴突容积分数、髓鞘容积分数和成像 g 比值，并探讨它们与 MS 患者神经功能障碍的关系。

材料和方法

对 30 名 MS 患者（23 名复发缓解型 MS，7 名进展型 MS）和 19 名年龄匹配的健康对照者进行了 3T MRI 扫描，该扫描仪配备了 300 mT/m 的最大梯度强度，采用了全面的多壳弥散 MRI 方案。大分子组织容积成像用于定量测量髓鞘容积分数。使用球形平均方法对弥散数据进行 3 室模型拟合，得出轴突容积分数的估计值。通过髓鞘容积分数与轴突容积分数的比值计算成像 g 比值。采用双侧检验和 Bonferroni 校正比较组间的影像学指标。

结果

病灶的平均 g 比值明显高于正常表现的白质（0.74 比 0.67， <.001）。病灶的轴突容积分数（0.17 比 0.23， <.001）和髓鞘容积分数（0.17 比 0.25， <.001）均明显低于正常表现的白质。正常表现的白质中的髓鞘容积分数也低于健康对照组（0.25 比 0.27， =.009）。扩展残疾状态量表（EDSS）测量的残疾程度与正常表现的白质中的髓鞘容积分数（β=-40.5， =.001）和轴突容积分数（β=-41.0， =.016）呈显著负相关。