基于电流扰动法阻抗测量的经颅电刺激装置研究

Transcranial Electrical Stimulation Device Based on Impedance Measurement of Current Perturbation Method

多通道经颅电刺激作为一种非侵入式神经刺激技术,具有更高的聚焦度和灵活度,但电极数的增加也加大了电极故障的风险,对电刺激装置的安全性和可靠性提出了更严格的要求。电极阻抗能反映皮肤接触状态及电极电化学变化,电极阻抗的在线监测有助于提高电刺激期间的安全性。由于多通道电刺激中存在串扰问题,直接测量电极阻抗误差较大,该文提出一种适用于多通道电刺激的新型在线阻抗测量方法,通过在刺激波形上叠加短时、小幅值电流扰动实现串扰解耦,从而测量各电极阻抗,实现对故障电极的定位。在上述方法的基础上,设计复合放大器增强型Howland电流源电路,采用现场可编程门阵列(FPGA)控制器,搭建多通道多模式经颅电刺激装置。最后通过该装置开展一系列人体实验研究,实现基于电流扰动法的电极阻抗在线监测,并在几类常见电极接触不良实验中成功定位故障电极。

As a non-invasive neurostimulation technique,multi-channel transcranial electrical stimulation has high focus and flexibility.However,the increase in the number of electrodes also increases the risk of electrode failure,and the requirements for the safety and reliability of the electrical stimulation device are more stringent.The electrode impedance can reflect the skin contact status and the electrochemical changes of the electrode,thus the online monitoring of the electrode impedance helps to improve the safety during electrical stimulation.Due to the crosstalk problem in multi-channel electrical stimulation,the direct measurement of electrode impedance has a large error.This paper proposes a new online impedance measurement method suitable for multi-channel electrical stimulation,which realizes crosstalk decoupling by superimposing short-term and small-amplitude current disturbances on the stimulation waveform,thereby measuring the impedance of each electrode and realizing the location of the faulty electrode.A composite amplifier enhanced Howland current source circuit was designed,and a multi-channel and a multi-mode transcranial electrical stimulation device was built using FPGA controller.Finally,a series of human body experiments were carried out through this device,the on-line monitoring of electrode impedance based on the current perturbation method was realized,and the faulty electrode was located in several types of common electrode poor contact experiments.