DataSheet1_Augmented Transcutaneous Stimulation Using an Injectable Electrode: A Computational Study.pdf

Minimally invasive neuromodulation technologies seek to marry the neural selectivity of implantable devices with the low-cost and non-invasive nature of transcutaneous electrical stimulation (TES). The Injectrode® is a needle-delivered electrode that is injected onto neural structures under image guidance. Power is then transcutaneously delivered to the Injectrode using surface electrodes. The Injectrode serves as a low-impedance conduit to guide current to the deep on-target nerve, reducing activation thresholds by an order of magnitude compared to using only surface stimulation electrodes. To minimize off-target recruitment of cutaneous fibers, the energy transfer efficiency from the surface electrodes to the Injectrode must be optimized. TES energy is transferred to the Injectrode through both capacitive and resistive mechanisms. Electrostatic finite element models generally used in TES research consider only the resistive means of energy transfer by defining tissue conductivities. Here, we present an electroquasistatic model, taking into consideration both the conductivity and permittivity of tissue, to understand transcutaneous power delivery to the Injectrode. The model was validated with measurements taken from (n = 4) swine cadavers. We used the validated model to investigate system and anatomic parameters that influence the coupling efficiency of the Injectrode energy delivery system. Our work suggests the relevance of electroquasistatic models to account for capacitive charge transfer mechanisms when studying TES, particularly when high-frequency voltage components are present, such as those used for voltage-controlled pulses and sinusoidal nerve blocks.

微创神经调控技术旨在将植入式设备的神经选择性与经皮电刺激（transcutaneous electrical stimulation, TES）的低成本、非侵入性特性相结合。Injectrode®是一种在影像引导下被注射至神经结构的针式递送电极，随后通过表面电极经皮向Injectrode®输送电能。Injectrode®作为低阻抗通路，可将电流引导至深层目标神经，与仅使用表面刺激电极相比，能将激活阈值降低一个数量级。为尽量减少皮肤纤维的非靶向募集，必须优化从表面电极到Injectrode®的能量传输效率。TES能量通过电容和电阻两种机制传递至Injectrode®。经皮电刺激研究中常用的静电有限元模型仅通过定义组织电导率来考虑电阻式能量传递方式。在此，我们提出一种电准静态模型（electroquasistatic model），同时考虑组织的电导率与介电常数，以探究经皮向Injectrode®输送电能的过程。该模型通过对（n=4）猪尸体的测量数据进行了验证。我们利用该经过验证的模型，对影响Injectrode®能量输送系统耦合效率的系统参数与解剖学参数展开了研究。我们的研究表明，在开展经皮电刺激相关研究时，考虑电容性电荷转移机制的电准静态模型具备重要意义，尤其当研究体系中存在高频电压分量时——例如电压控制脉冲与正弦神经阻滞所使用的电压分量。