IEEE Trans Neural Syst Rehabil Eng. 2020 Dec;28(12):2901-2913. doi: 10.1109/TNSRE.2020.3038406. Epub 2021 Jan 28.
Although magnetic neural stimulation has many advantages over electrical neural stimulation, its main disadvantages are higher energy requirement and poor stimulation selectivity. The orientation and location of the coil with respect to the stimulation site play a critical role in determining the stimulation threshold and stimulation selectivity. Utilizing numerical simulations in this work, we optimized the design parameters, orientation, and positioning of magnetic coils with respect to the peripheral nerve for improved stimulation efficacy. Specifically, we investigated different orientations and positions of the figure-of-eight coils for neural stimulation of the rat sciatic nerve. We also examined the effect of coil design parameters (number of layers and turns) and different coil electrical configurations (opposite vs. same direction of coil currents and series vs. parallel coil connections) on the stimulation threshold. We leveraged the multi-resolution impedance method and a heterogeneous multi-fascicular anatomical model of rat sciatic nerve to explore the possibility of selective stimulation as well. Neural excitation of a nerve fiber was implemented by an equivalent cable model and Frankenhaeuser-Huxley equations using NEURON software. Results suggest that inter-fascicular selectivity could be achieved by properly orienting and positioning the coil with respect to the nerve. Further, by orienting the figure-of-eight coil at an angle of 90° and 6 mm offset, we could switch between primarily activating one fascicle (and barely activating the other) and reversing those roles by merely switching the current direction in the two coils of the figure-of-eight coil.
尽管磁神经刺激相对于电神经刺激具有许多优势,但它的主要缺点是能量需求更高且刺激选择性较差。线圈相对于刺激部位的方向和位置在确定刺激阈值和刺激选择性方面起着关键作用。在这项工作中,我们利用数值模拟优化了磁线圈的设计参数、方向和位置,以提高刺激效果。具体来说,我们研究了不同取向和位置的 8 字形线圈对大鼠坐骨神经的神经刺激。我们还研究了线圈设计参数(层数和匝数)以及不同线圈电配置(线圈电流方向相反与相同,以及线圈串联与并联)对刺激阈值的影响。我们利用多分辨率阻抗法和大鼠坐骨神经的异质多束解剖模型来探索选择性刺激的可能性。使用神经元软件,通过等效电缆模型和 Frankenhaeuser-Huxley 方程来实现神经纤维的兴奋。结果表明,通过适当调整线圈相对于神经的方向和位置,可以实现束间选择性。此外,通过将 8 字形线圈以 90°的角度和 6 毫米的偏移量定位,可以在主要激活一个束(几乎不激活另一个束)和反转这些作用之间切换,只需切换 8 字形线圈中两个线圈的电流方向即可。
IEEE Trans Neural Syst Rehabil Eng. 2020-12
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