Gradient echo based fiber orientation mapping using R2*and frequency difference measurements
Gradient echo based fiber orientation mapping using R2*and frequency difference measurements
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DOI：
10.1016/j.neuroimage.2013.07.054
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发表时间：
2013-12-01
期刊：
影响因子：
5.7
通讯作者：
Bowtell, Richard
中科院分区：
文献类型：
--
作者：
Wharton, Samuel;Bowtell, Richard
通过扩散张量成像（DTI）进行纤维定向映射是一种功能强大的基于MRI的技术，用于可视化大脑中的白色物质（WM）微观结构。尽管DTI提供了一种测量纤维取向的稳健方法，但它具有与EPI读出和长扩散编码周期的使用相关的一些限制，包括相对较低的空间分辨率。因此，开发替代的基于MRI的纤维取向映射方法是有价值的，部分原因是为了验证DTI结果。在这项研究中，我们使用R2 *（1 [12 *）和频率差测量的方向依赖性，从多回波梯度回波（GE）图像中生成WM中纤维方向的三维图，该图像是从死后脑组织样本中以多个角度定向到Bo的。通过解析推导和数值模拟，R2 * 和频率差值的变化与底层WM纤维取向和B0方向之间的角度的关系的特点。高分辨率的3D纤维取向图（FOM），然后通过比较R2 * 和频率差数据，获得与样品在多个方向的字段，广义模型的基础上推导出的表达式的角度依赖性的每个参数。通过比较所得到的GE为基础的FOM与DTI为基础的FOM从相同的组织样本，我们表明，基于梯度回波MRI的纤维取向映射有可能成为一个重要的工具，研究脑组织中的微观结构。(C)2013 Elsevier Inc. All rights reserved.
Fiber orientation mapping through diffusion tensor imaging (DTI) is a powerful MRI-based technique for visualising white matter (WM) microstructure in the brain. Although DTI provides a robust way to measure fiber orientation, it has some limitations linked to the use of EPI read-outs and long diffusion encoding periods, including relatively low spatial resolution. Development of alternative MRI-based methods for fiber orientation mapping is therefore valuable, in part to allow validation of DTI results. In this study, we used the orientation dependence of R2* (1[12*) and frequency difference measurements to generate three dimensional maps of the fiber orientation in WM from multi-echo gradient-echo (GE) images acquired from post mortem brain tissue samples oriented at multiple angles to Bo. Through analytical derivation and numerical simulation, the relationships connecting variations in R2* and frequency difference values to the angle between the underlying WM fiber orientation and the direction of B0 were characterised. High resolution 3D fiber orientation maps (FOM) were then formed by comparing R2* and frequency difference data, acquired with the sample at multiple orientations to the field, to generalised models based on the derived expressions for the angular dependence of each parameter. By comparing the resulting GE-based FOM with DTI-based FOM from the same tissue sample, we demonstrate that fiber orientation mapping based on gradient echo MRI has the potential to become an important tool for investigating microstructure in brain tissue. (C) 2013 Elsevier Inc. All rights reserved.