How and how not to correct for CSF-contamination in diffusion MRI
How and how not to correct for CSF-contamination in diffusion MRI
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DOI：
10.1016/j.neuroimage.2011.08.043
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发表时间：
2012-01-16
期刊：
影响因子：
5.7
通讯作者：
Jones, Derek K.
中科院分区：
文献类型：
--
作者：
Metzler-Baddeley, Claudia;O'Sullivan, Michael J.;Jones, Derek K.
弥散MRI广泛用于研究与脑发育和病理学相关的白色物质微观结构的变化。然而，老化也与显著的白色和灰质损失相关，这反过来又会导致扩散MRI度量中基于脑脊液（CSF）的部分体积伪影。这在容易受到CSF污染的区域尤其成问题，例如分别穿过或靠近脑室的穹窿和胼胝体的穹窿。本研究的目的是模拟CSF污染对扩散MRI指标的影响，并评估不同的采集后策略，以纠正CSF污染：控制全脑体积，并使用自由水消除（FWE）方法在体素基础上进行校正。使用穹窿作为易于CSF污染的结构的范例，对来自39名老年人（53 - 93岁）的经验DT-MRI数据的基于束和基于体素的[基于束的空间统计（TBSS）]分析进行校正。除了全脑体积和穹窿组织体积分数的显著年龄相关性降低外，年龄还与平均各向异性分数降低和穹窿扩散率指标增加相关。实验数据与模拟结果一致，扩散率指标（平均扩散率，轴向和径向扩散率）比分数各向异性更容易出现部分体积CSF污染错误。基于FWE的体素的体素部分体积校正后，年龄和扩散率指标，特别是轴向扩散率之间的显着正相关性消失，而与各向异性的相关性仍然存在。相比之下，校正全脑容量对消除这些虚假相关性几乎没有影响。我们的研究强调了在推断白色物质结构的潜在变化之前，在逐体素的基础上校正感兴趣结构中CSF污染部分体积效应的重要性，并对许多最近的扩散MRI结果在衰老和疾病中的解释产生影响。(C)2011 Elsevier Inc. All rights reserved.
Diffusion MRI is used extensively to investigate changes in white matter microstructure related to brain development and pathology. Ageing, however, is also associated with significant white and grey matter loss which in turn can lead to cerebrospinal fluid (CSF) based partial volume artefacts in diffusion MRI metrics. This is especially problematic in regions prone to CSF contamination, such as the fornix and the genu of corpus callosum, structures that pass through or close to the ventricles respectively. The aim of this study was to model the effects of CSF contamination on diffusion MRI metrics, and to evaluate different post-acquisition strategies to correct for CSF-contamination: Controlling for whole brain volume and correcting on a voxel-wise basis using the Free Water Elimination (FWE) approach. Using the fornix as an exemplar of a structure prone to CSF-contamination, corrections were applied to tract-specific and voxel-based [tract based spatial statistics (TBSS)] analyses of empirical DT-MRI data from 39 older adults (53-93 years of age). In addition to significant age-related decreases in whole brain volume and fornix tissue volume fraction, age was also associated with a reduction in mean fractional anisotropy and increase in diffusivity metrics in the fornix. The experimental data agreed with the simulations in that diffusivity metrics (mean diffusivity, axial and radial diffusivity) were more prone to partial volume CSF-contamination errors than fractional anisotropy. After FWE-based voxel-by-voxel partial volume corrections, the significant positive correlations between age and diffusivity metrics, in particular with axial diffusivity, disappeared whereas the correlation with anisotropy remained. In contrast, correcting for whole brain volume had little effect in removing these spurious correlations. Our study highlights the importance of correcting for CSF-contamination partial volume effects in the structures of interest on a voxel-by-voxel basis prior to drawing inferences about underlying changes in white matter structures and have implications for the interpretation of many recent diffusion MRI results in ageing and disease. (C) 2011 Elsevier Inc. All rights reserved.