Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure
Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure
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DOI：
10.1073/pnas.0910222107
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发表时间：
2010-03-16
影响因子：
11.1
通讯作者：
Duyn, Jeff H.
中科院分区：
文献类型：
--
作者：
Lee, Jongho;Shmueli, Karin;Duyn, Jeff H.
高场（>= 7 T）MRI的最新进展使得在纤维束和皮质层水平上研究人脑的精细结构成为可能。特别是，旨在检测源于磁化率和其他来源的局部变化的MRI共振频率偏移的技术已经大大改善了这些结构的可视化。最近的理论研究[He X，Yablonskiy DA（2009）Proc Natl Acad Sci USA 106：13558-13563]表明，MRI共振频率不仅可以报告组织组成，而且可以报告磁化率内含物的微观区室化及其相对于磁场的取向。所提出的对组织结构的敏感性可以极大地扩展常规MRI技术可用的信息。为了研究这种可能性，我们研究了死后的组织样本，从人类胼胝体的实验设计，允许分离的微观结构的影响混淆宏观结构的影响。结果表明，MRI共振频率确实依赖于微结构取向。此外，共振频率偏移的空间分布表明起源与各向异性磁化率效应有关，而不是微观划分。这种各向异性，已被证明取决于分子排序，可以提供有价值的信息组织分子结构。
Recent advances in high-field (>= 7 T) MRI have made it possible to study the fine structure of the human brain at the level of fiber bundles and cortical layers. In particular, techniques aimed at detecting MRI resonance frequency shifts originating from local variation in magnetic susceptibility and other sources have greatly improved the visualization of these structures. A recent theoretical study [He X, Yablonskiy DA (2009) Proc Natl Acad Sci USA 106:13558-13563] suggests that MRI resonance frequency may report not only on tissue composition, but also on microscopic compartmentalization of susceptibility inclusions and their orientation relative to the magnetic field. The proposed sensitivity to tissue structure may greatly expand the information available with conventional MRI techniques. To investigate this possibility, we studied postmortem tissue samples from human corpus callosum with an experimental design that allowed separation of microstructural effects from confounding macrostructural effects. The results show that MRI resonance frequency does depend on microstructural orientation. Furthermore, the spatial distribution of the resonance frequency shift suggests an origin related to anisotropic susceptibility effects rather than microscopic compartmentalization. This anisotropy, which has been shown to depend on molecular ordering, may provide valuable information about tissue molecular structure.