Lorentzian effects in magnetic susceptibility mapping of anisotropic biological tissues.
Lorentzian effects in magnetic susceptibility mapping of anisotropic biological tissues.
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DOI：
10.1016/j.jmr.2018.04.014
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发表时间：
2018-07
期刊：
影响因子：
--
通讯作者：
Sukstanskii AL
中科院分区：
文献类型：
--
作者：
Yablonskiy DA;Sukstanskii AL
MRI的最终目的是提供生物组织的微观结构和功能信息。定量磁敏感成像（QSM）是一种通过测量梯度回波（GRE）MRI信号相位来研究组织微结构的新方法。这种方法的核心问题是：来自成像体素的GRE信号的净相位/频率与细胞和亚细胞水平的底层组织微结构之间的关系是什么？在存在外部磁场的情况下，生物介质（例如，细胞、细胞成分、血液）被磁化，导致MR信号频移，其不仅受到体磁化率的影响，而且还受到局部细胞环境的影响。后一种效应通常被称为对频率偏移的洛伦兹贡献。评估的洛伦兹贡献-在这一领域中最有趣和最具挑战性的问题之一-是本次审查的主要重点。虽然传统的方法来解决这个问题是基于一个虚构的洛伦兹腔的介绍，最近提出了一个更严格的治疗的基础上的统计方法和直接的解决方案的麦克斯韦方程。这种方法，被称为广义洛伦兹张量方法（GLTA），是特别富有成效的描述各向异性生物介质。GLTA充分考虑了两种类型的各向异性：磁化率的各向异性和组织结构各向异性（例如，白色物质中的圆柱形轴突束）。在GLTA的框架中，由于局部环境引起的频率偏移用洛伦兹张量L来描述，其可以具有与磁化率张量χ基本上不同的结构。虽然χ的组分是通过其体积分数“加权”的隔室渗透率，但L的组分另外通过取决于细胞几何对称性的特定数值因子加权。除了描述作为主要基于考虑系统对称性的现象学方法的GLTA之外，我们还简要地讨论了基于在不同状态（即，静态失相与运动变窄）和不同细胞环境（例如，考虑WM微结构）。
The ultimate goal of MRI is to provide information on biological tissue microstructure and function. Quantitative Susceptibility Mapping (QSM) is one of the newer approaches for studying tissue microstructure by means of measuring phase of Gradient Recalled Echo (GRE) MRI signal. The fundamental question in the heart of this approach is: what is the relationship between the net phase/frequency of the GRE signal from an imaging voxel and the underlying tissue microstructure at the cellular and sub-cellular levels? In the presence of external magnetic field, biological media (e.g. cells, cellular components, blood) become magnetized leading to the MR signal frequency shift that is affected not only by bulk magnetic susceptibility but by the local cellular environment as well. The latter effect is often termed the Lorentzian contribution to the frequency shift. Evaluating the Lorentzian contribution - one of the most intriguing and challenging problems in this field – is the main focus of this review. While the traditional approach to this problem is based on introduction of an imaginary Lorentzian cavity, a more rigorous treatment was proposed recently based on a statistical approach and a direct solution of the Maxwell equations. This approach, termed the Generalized Lorentzian Tensor Approach (GLTA), is especially fruitful for describing anisotropic biological media. The GLTA adequately accounts for two types of anisotropy: anisotropy of magnetic susceptibility and tissue structural anisotropy (e.g., cylindrical axonal bundles in white matter). In the framework of the GLTA the frequency shift due to the local environment is described in terms of the Lorentzian tensor L̂ which can have a substantially different structure than the susceptibility tensor χ̂. While the components of χ̂ are compartmental susceptibilities “weighted” by their volume fractions, the components of L̂ are additionally weighted by specific numerical factors depending on cellular geometrical symmetry. In addition to describing the GLTA that is a phenomenological approach largely based on considering the system symmetry, we also briefly discuss a microscopic approaches to the problem that are based on modeling of the MR signal in different regimes (i.e. static dephasing vs. motion narrowing) and in different cellular environments (e.g., accounting for WM microstructure).
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影响因子：
3.3
作者：
Wang, Yi;Liu, Tian
通讯作者：
Liu, Tian
影响因子：
3.3
作者：
Wharton, Samuel;Bowtell, Richard
通讯作者：
Bowtell, Richard
磁敏感性引起的白质MR信号频率转移 - 洛伦兹球体和广义洛伦兹方法之间的实验比较。
影响因子：
3.3
作者：
Luo, J.;He, X.;Yablonskiy, D. A.
通讯作者：
Yablonskiy, D. A.
影响因子：
3.3
作者：
Sukstanskii, Alexander L.;Yablonskiy, Dmitriy A.
通讯作者：
Yablonskiy, Dmitriy A.
DOI：
10.1073/pnas.0910222107
发表时间：
2010-03-16
影响因子：
11.1
作者：
Lee, Jongho;Shmueli, Karin;Duyn, Jeff H.
通讯作者：
Duyn, Jeff H.