视觉假体电刺激波形的改进研究

发布时间：2018-11-28 07:15

【摘要】：研究目的视觉假体是对盲人视觉通路上某个神经组织结构施加人工电刺激,使其产生兴奋,在皮层产生视觉感知的植入式医用电子设备。视觉假体的目的是使那些由于疾病或外伤导致失明的患者通过人工的方法产生视觉感知,辅助他们完成一些活动,如阅读文本,识别物体或应对陌生环境等。视觉假体研究的主要内容之一是提高神经刺激的有效性。电刺激脉冲波形的形状(包括幅度、频率、脉宽等)和电极几何结构是影响有效神经刺激的重要因素。脉冲波形的形状直接影响电刺激时的组织损伤、电极腐蚀和电荷损失等,因此选择合适的脉冲波形对有效降低电刺激时引起的负作用至关重要。鉴于矩形双相脉冲波形相比于其他脉冲波形(线性波,正弦波,指数波等)在视觉假体电刺激中使用较为普遍,本文选择相对较成熟的矩形双相波形来进行优化设计,来获得更理想的刺激效果。研究内容 1视觉假体电刺激仿真。用MATLAB平台下的Simulink仿真电极刺激生理组织的过程,电极——组织界面使用Randles电极——电解液界面等效电路模型,输入波形使用优化的矩形波,观察峰值电压、功率和能量等结果。 2矩形双相波的优化设计。利用控制系统理论中零阶保持器的特性,在波形输入装置后加入零阶保持器,使得通常恒定电流刺激相由定期采样的阶梯形波取代,以此作为优化的矩形波。改变零阶保持器的参数可使优化波形的幅度和时间发生变化,使之成为二阶、三阶等阶梯形波。 3视觉假体电刺激优化电流波形的刺激效果。电极——电解液界面等效电路的输入电流脉冲波形为优化的阶梯形波,计算优化电流波形输入等效电路后的峰值电压、功率和能量；与原始矩形波的刺激效果进行对比,分析比较优化波形相对于传统矩形波的特点。研究结果 1视觉假体电刺激矩形波经优化后成为阶梯形波。改变参数可使优化波形成为二阶、三阶等多阶阶梯形波。优化的二阶阶梯形波输入时,输出电压峰值减少了11.05%；五阶阶梯形波时其峰值电压下降达到了11.89%。 2在峰值电压减少的同时,等效电路模型中的平均功率和瞬时功率也发生了变化。五阶阶梯形波的平均功率减少率最大,为10.13%。二阶、三阶等多阶阶梯形波的瞬时功率增大较为明显,但五阶阶梯形波的最大瞬时功率增大只有7.75%,相比于其他阶梯形波较为理想。 3系统的能量消耗随着电极峰值电压的减少也出现了降低,而且阶梯形波的阶数越多,其能量消耗减少越大,在阶数趋近于无穷大时能量消耗减少了11.79%,而五阶阶梯形波的能量消耗减少了5.96%。研究结论： 1矩形波优化为阶梯形波后,具有明显的降低峰值电压的效果。五阶阶梯形波减少峰值电压达到最大。优化波形达到了降低电路电压减少组织损伤的目的。 2功率和电路耗能同时是优化波形的衡量标准。五阶阶梯形波的瞬时功率的功率增大率最小,平均功率的减少率最大。系统耗能随着阶数的增大而逐渐减小,在阶数趋近于无穷时达到最大。 3五阶阶梯形波虽然没有达到能耗减少最大,但是却能够使峰值电压减少最大,平均功率减少最大,瞬时功率增大最小,因此五阶阶梯形波是较为理想的优化的阶梯形波。
[Abstract]:Purpose of the study The visual prosthesis is an implantable medical electronic device for applying artificial electrical stimulation to a nerve tissue structure on the visual path of the blind, The purpose of the visual prosthesis is to make visual perception of those who are blind due to disease or trauma, and to assist them in completing some of the activities, such as reading text, identifying objects, or dealing with unfamiliar environments and the like. One of the main contents of the visual prosthesis study is to increase the nerve stimulation. Effectiveness. The shape of the electrical stimulation pulse waveform (including amplitude, frequency, pulse width, etc.) and the electrode geometry are the weight that affects the effective nerve stimulation. the shape of the pulse waveform directly influences the tissue damage, the electrode corrosion and the charge loss when the electrical stimulation is applied, so that the appropriate pulse waveform is selected to effectively reduce the negative effect caused when the electric stimulation is effectively reduced, It is important to use a relatively mature rectangular two-phase waveform for optimal design in view of the fact that the rectangular two-phase pulse waveform is more common than other pulse waveforms (linear wave, sine wave, exponential wave, etc.) compared with other pulse waveforms (linear wave, sine wave, exponential wave, etc.). shock effect. Study content 1 Visual Prosthesis Electrical stimulation simulation. The process of stimulating the physiological tissue by using the Simulink simulation electrode under the MATLAB platform, the electrode _ tissue interface uses the Randles electrode _ electrolyte interface equivalent circuit model, the input waveform uses the optimized rectangular wave, and the peak voltage, the power and the power are observed. result of energy, etc. 2 rectangular double The optimal design of phase wave. With the characteristic of the zero-order holder in the theory of the control system, a zero-order holder is added to the waveform input device, so that the constant-current stimulation phase is replaced by a regular-sampled stepped wave, changing the parameters of the zero-order holder may cause the amplitude and time of the optimized waveform to change, making it a second order, third-order stepped-wave. 3-visual prosthetic electrical stimulation optimization The stimulation effect of the current waveform is that the input current pulse waveform of the electrode _ electrolyte interface equivalent circuit is the optimized stepped wave, and the peak voltage, the power and the energy after the equivalent circuit of the optimized current waveform are input; and the original rectangular wave and compared with the stimulation effect, the comparative optimization waveform is analyzed and compared with each other, traditional moment Characteristics of the shape wave. The results of the study are 1. The electrical stimulation of the visual prosthesis is rectangular. the wave is optimized to form a stepped wave, and the change parameter can make the optimized wave form a two-step wave. In order to optimize the second-order step-wave input, the peak value of the output voltage is reduced by 11. 05%, and the peak voltage at the time of the step-step wave of the fifth order the drop has reached 11.89%. At the same time the peak voltage is reduced, the average value of the equivalent circuit model the power and the instantaneous power also change. the average power of the fifth-order stepped wave and the maximum instantaneous power of the five-order stepped wave is increased by only 7.75%, Compared with other stepped waves, the energy consumption of the system decreases with the reduction of the peak voltage of the electrode, and the higher the order number of the stepped wave, the higher the energy consumption, the energy consumption is reduced by 11. 79% when the order number approaches infinity, and the five-step ladder energy of a wave The consumption is reduced by 5.96%. The results of the study: 1 rectangular wave is optimized to be stepped After the wave, it has the obvious effect of reducing the peak voltage.. The step-step wave of the fifth order reduces the peak voltage to the maximum. the purpose of reducing the circuit voltage to reduce tissue damage is reached. The power and circuit energy consumption are the measure of the optimization of the waveform. The instantaneous power of the step-step wave of the fifth order The power increase rate of the system is the minimum, and the reduction rate of the average power is the maximum. The energy consumption of the system increases with the order number. and the peak voltage is reduced to the maximum, the average power is reduced to the maximum, and the instantaneous power is increased to a minimum,
【学位授予单位】：天津医科大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：R318.18

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