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Estimation of Induced Eddy Current in the Brain and Characteristics of Nerve Excitation by Magnetic Stimulation

脑内感应涡流的估计和磁刺激神经兴奋的特征

基本信息

批准号：
07680949
负责人：
YUNOKUCHI Kazutomo
金额：
$ 0.83万
依托单位：
Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07680949/
关键词：
magnetic stimulation distributions of induced eddy current cranium model bull frog's sciatic nerve arm tank model

项目摘要

In recent years, the contactless and non-invasive magnetic stimulation is used to diagnose the function of nerve in the clinical application. In magnetic stimulation, it is important for clarifying the location of nerve excitation to estimate the distributions of induces eddy current in a living body. It is, however, difficult to predict distributions of induced eddy currents in an inhomogeneous medium like as the humanbrain. In order to investigate the characteristics of induced eddy currents in the cranium, the distributions of induced eddy current in the simple cranium model which is filled with the saline solution was measured by the probe made of a thin flexible mini coaxial cable. Moreover, the estimation of the stimulated point in the nerve was performed by using the nerve muscle model of a bull frog's sciatic nerve.The purpose of this study is to find out the distributions of induced eddy current generated in the cranial model filled with the saline solution, when the model was exposed to pulsed magnetic fields. We discussed the relationship between a focality of the induced eddy currents and an excited location in the head due to the orientation of the coil. As a result, the distribution of induced eddy current depends on the structure of boundary of the skull or narrow space. This experiment showed that the highest density of induced eddy currents provided a result when the current flowed in the vicinity of the rear edge of foramen occipitale magnum. The intensity of induced eddy currents at the foramen magnum differs a little due to the direction of current flow. From the results of the nerve muscle model in the internal acoustic meatus by the magnetic stimulation, it is showed that the nerve is easy to be stimulated at where the change of induced eddy current density is very large or the nerve is bent in the finite medium, for example an arm tank model.

近年来，无接触、无创的磁刺激技术在临床上被用于神经功能的诊断。在磁刺激中，估计生物体内感应涡电流的分布对于明确神经兴奋的位置是重要的。然而，在非均匀介质（如人脑）中，很难预测感应涡流的分布。为了研究颅骨内感生涡流的特性，采用细同轴电缆探头测量了简单颅骨模型内的感生涡流分布。利用牛蛙坐骨神经的神经肌肉模型对神经刺激点进行了估计，研究了充有生理盐水的颅骨模型在脉冲磁场作用下产生的感应涡流的分布。我们讨论了感应涡流的焦点和由于线圈的方向在头部中的激励位置之间的关系。因此，感应涡流的分布取决于颅骨或狭窄空间的边界结构。实验结果表明，当电流在枕大孔后缘附近流动时，感应涡电流密度最高。在枕骨大孔处的感应涡流的强度由于电流流动的方向而略有不同。磁刺激内听道神经肌肉模型的结果表明，在有限介质中感应涡流密度变化很大或神经弯曲的地方，如手臂坦克模型，神经容易受到刺激。