Magnetic pesonance imaging of electrical conductivity in the human brain
Magnetic pesonance imaging of electrical conductivity in the human brain
复制标题
人脑电导率的磁共振成像
DOI：
10.1109/tmag.2005.854804
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
S. Ueno
中科院分区：
文献类型：
--
作者：
M. Sekino;Y. Inoue;S. Ueno
在这项研究中，使用1.5磁共振成像系统获得了人脑的电导率分布。MR成像采用运动探测梯度(MPG)，沿三个垂直方向以25个等间距b因子进行扫描，b因子从200到5000 S/mm~2。B因子定义为b=Gamma2G2delta2(Delta-Delta/3)，其中Gamma是旋磁比(2.7×108rad S-1T-1)，G和Delta分别是MPG的强度和持续时间，Delta是MPG前沿之间的间隔。结果表明，随着b因子的增加，磁共振图像的信号强度减弱。MPG在上下方向上的应用导致信号衰减最快。信号衰减的各向异性可以归因于组织的纤维结构。壳核和内囊的平均电导率分别为0.066 S/m和0.80 S/m。在内囊中，神经纤维方向的电导率表现出较高的值。与壳核相比，该区域的各向异性指数(AI)较高。低频电流主要通过离子在细胞外空间的迁移来传导。由于电导率模型只考虑了胞外电流，因此所采用的方法计算的电导率对应于极低频率下的值。
In this study, conductivity distribution of the human brain were obtained using 1.5 magnetic resonance (MR) imaging system. MR images were obtained with motion-probing gradients (MPGs) applied in three orthogonal directions at 25 equally spaced b factors from 200 to 5000 s/mm2. The b factor was defined as b = gamma2G 2delta2(Delta - delta/3), where gamma is the gyromagnetic ratio (2.7 times 108 rad s-1 T -1), G and delta are the respective intensity and duration of the MPGs, and Delta is the interval between the leading edges of the MPGs. Results show that the signal intensities of MR images are attenuated with an increase in the b factor. An application of the MPG in the superior-inferior direction caused the most rapid signal attenuation. The anisotropy of signal attenuations can be attributed to the fibrous structures of the tissue. The mean conductivity (MC) values of the putamen and the internal capsule were 0.066 S/m and 0.80 S/m, respectively. In the internal capsule, the conductivity exhibited high value in the directions of neuronal fibers. This region had high anisotropy index (AI) in comparison with the putamen. Low-frequency currents are mainly conducted via migrations of ions through extracellular space. The conductivity calculated by the method employed corresponds to the values at very low frequencies because the conductivity model considers only the extracellular current