White matter microstructure from nonparametric axon diameter distribution mapping.
White matter microstructure from nonparametric axon diameter distribution mapping.
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DOI：
10.1016/j.neuroimage.2016.04.052
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发表时间：
2016-07-15
期刊：
影响因子：
5.7
通讯作者：
Basser PJ
中科院分区：
文献类型：
--
作者：
Benjamini D;Komlosh ME;Holtzclaw LA;Nevo U;Basser PJ
我们报告了一种双扩散编码（DDE） MRI方法的发展，用于估计和绘制成像体积内轴突直径分布（ADD）。多种生物过程，从发育到疾病和创伤，都可能导致中枢和外周神经系统ADD的变化。与之前提出的方法不同，这种ADD实验设计和估计框架采用了更一般的非参数方法，没有对ADD的潜在形式进行先验假设，使其适合分析异常组织。在目前的研究中，该框架被用于离体雪貂脊髓，同时强调了通过轴突的数量或体积来加权ADD的方式。不同的权重，导致不同的空间对比，在整个工作中被考虑。对DDE数据进行分析，得出平均轴突直径、ADD方差和轴突外体积分数的空间分辨图，以及一种新的亚微米限制结构图。利用基于空间连续性和左右对称约束的k-means聚类算法，利用这些图谱中的形态学信息将脑白质划分为不同的区域，从而得到可识别的脑白质轨迹。通过使用定量相似性度量将组织学测量值与估计的add进行比较，验证了该方法，结果吻合良好。随着进一步的采集加速和实验参数的调整，这种ADD估计框架可以首先用于临床前，最终用于临床，从而实现广泛的神经影像学应用，以提高对神经退行性病理的理解，并评估创伤引起的微结构变化。
We report the development of a double diffusion encoding (DDE) MRI method to estimate and map the axon diameter distribution (ADD) within an imaging volume. A variety of biological processes, ranging from development to disease and trauma, may lead to changes in the ADD in the central and peripheral nervous systems. Unlike previously proposed methods, this ADD experimental design and estimation framework employs a more general, nonparametric approach, without a priori assumptions about the underlying form of the ADD, making it suitable to analyze abnormal tissue. In the current study, this framework was used on an ex vivo ferret spinal cord, while emphasizing the way in which the ADD can be weighted by either the number or the volume of the axons. The different weightings, which result in different spatial contrasts, were considered throughout this work. DDE data were analyzed to derive spatially resolved maps of average axon diameter, ADD variance, and extra-axonal volume fraction, along with a novel sub-micron restricted structures map. The morphological information contained in these maps was then used to segment white matter into distinct domains by using a proposed k-means clustering algorithm with spatial contiguity and left–right symmetry constraints, resulting in identifiable white matter tracks. The method was validated by comparing histological measures to the estimated ADDs using a quantitative similarity metric, resulting in good agreement. With further acquisition acceleration and experimental parameters adjustments, this ADD estimation framework could be first used preclinically, and eventually clinically, enabling a wide range of neuroimaging applications for improved understanding of neurodegenerative pathologies and assessing microstructural changes resulting from trauma.