Department of Computing Science and Mathematics, School of Informatics and Creative Arts, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland.
UCD School of Electrical and Electronic Engineering, University College Dublin, Belfield, Dublin 4, Ireland.
Med Eng Phys. 2019 Mar;65:61-67. doi: 10.1016/j.medengphy.2018.12.018. Epub 2019 Jan 16.
Parametric models are commonly used to describe the dispersive dielectric properties of biological tissues. While distinct regions of dispersion have been identified, the relative contribution of each during electrical stimulation is unknown. This study quantified the contribution of individual poles in parametric models of brain and muscle dielectric properties during electrical stimulation. The effect on the extracellular voltage waveform and threshold current for nerve stimulation of selectively removing subsets of poles from Cole-Cole and Debye models was examined. Errors were introduced when dispersions below 100 kHz were removed in both brain and muscle tissue. Poles below 1 kHz influenced the amplitude of the extracellular voltage waveform and the predicted minimum stimulation current. Poles between 1 kHz and 100 kHz influenced the waveform shape, with a minor effect on stimulus amplitude. The results confirm that low frequency dispersion in conductivity and permittivity can fundamentally influence the electric field and neural response during stimulation and provide insight into the relative contribution of the different dispersive regimes. Furthermore, they provide justification for for simplifying parametric models of dielectric properties through the removal of high frequency poles above 100 kHz which could improve the efficiency of time-domain solvers for simulations involving time-varying or aperiodic stimuli as may be required for certain closed-loop stimulation paradigms.
参数模型常用于描述生物组织的弥散介电特性。虽然已经确定了不同的弥散区域，但在电刺激过程中每个区域的相对贡献尚不清楚。本研究量化了在电刺激期间大脑和肌肉介电特性的参数模型中各个极点的贡献。研究考察了从 Cole-Cole 和 Debye 模型中选择性去除极点子集对神经刺激的细胞外电压波形和阈电流的影响。在脑组织和肌肉组织中去除低于 100 kHz 的弥散时会引入误差。1 kHz 以下的极点会影响细胞外电压波形和预测的最小刺激电流的幅度。1 kHz 至 100 kHz 之间的极点会影响波形形状，对刺激幅度的影响较小。研究结果证实，在刺激过程中，电导率和介电常数的低频弥散可以从根本上影响电场和神经反应，并深入了解不同弥散状态的相对贡献。此外，它们为通过去除高于 100 kHz 的高频极点来简化介电特性的参数模型提供了依据，这可以提高涉及时变或非周期刺激的时域求解器的效率，因为某些闭环刺激范式可能需要这样的刺激。
