Gawryluk Jodie R, Brewer Kimberly D, Beyea Steven D, D'Arcy Ryan C N
Institute for Biodiagnostics, National Research Council, Halifax, Nova Scotia, Canada.
Neuroimage. 2009 Mar 1;45(1):83-8. doi: 10.1016/j.neuroimage.2008.11.005. Epub 2008 Nov 21.
The majority of functional magnetic resonance imaging (fMRI) studies restrict their focus to gray matter regions because this tissue is highly perfused relative to white matter. However, an increasing number of studies are reporting fMRI activation in white matter. The current study had two objectives: 1) to evaluate whether it is possible to detect white matter fMRI activation and 2) to determine whether certain MRI contrast mechanisms are more sensitive to white matter activation (i.e., BOLD contrast- versus T(2)-weighting). Data were acquired from a 4 T MRI using an asymmetric spin echo spiral sequence (ASE spiral). This technique collected three images with equal BOLD contrast weighting and increasing T(2)-weighting. An interhemispheric transfer task was used to elicit activation in the corpus callosum. White matter fMRI activation was examined for the averaged ASE spiral data and for each image separately. Callosal activation was present in all subjects as well as in the group analysis. Analyses revealed that increasing T(2) contrast improved sensitivity as measured by percent signal change. The results suggest that it is possible to detect white matter activation in fMRI and that ASE spiral showed increasing sensitivity to this activation as a function of T(2)-weighting. The findings provide further support for the investigation of white matter fMRI.
大多数功能磁共振成像（fMRI）研究将重点局限于灰质区域，因为相对于白质而言，该组织的灌注程度很高。然而，越来越多的研究报告称白质中存在fMRI激活。本研究有两个目标：1）评估是否有可能检测到白质fMRI激活；2）确定某些MRI对比机制对白质激活是否更敏感（即血氧水平依赖（BOLD）对比与T(2)加权）。使用非对称自旋回波螺旋序列（ASE螺旋）从4T磁共振成像中获取数据。该技术采集了三张具有相等BOLD对比加权且T(2)加权递增的图像。采用半球间转移任务来诱发胼胝体的激活。对ASE螺旋平均数据以及每张图像分别检查白质fMRI激活情况。所有受试者以及在组分析中均存在胼胝体激活。分析表明，以信号变化百分比衡量，增加T(2)对比可提高敏感性。结果表明，在fMRI中检测白质激活是可能的，并且ASE螺旋对白质激活的敏感性随T(2)加权增加而提高。这些发现为白质fMRI研究提供了进一步的支持。
