Waugaman W A
University of Colorado, Electrical Engineering Program, Boulder, CO 80309, USA.
Biomed Sci Instrum. 1999;35:367-72.
Therapeutic electrical stimulation (TES) is a rehabilitative stimulation therapy for individuals with neuromuscular disorders. TES uses subthreshold transcutaneous electrical stimulation to cause muscle growth and neuron sprouting through increased blood flow. To optimize TES therapy, a new method was required to determine the electrical current density in the target muscle. This is because TES's subthreshold stimulation intensity does not produce any measurable physiological effect. The finite element method (FEM) was the numerical modeling method chosen. FEM provides the ability to the model complex properties found in living beings, such as different tissue types and anisotropic tissue properties. TES uses a 35 Hz biphasic waveform. At this low frequency, the quasi-static approximation was used. This allows the heat transfer model solution to be used to find the steady state electric field solution. The goal of this paper is to show that the heat transfer results are the same as the electric field measurements made in a biological phantom. Laboratory measurements were made in a one liter cylinder of normal saline using bipolar stimulation. Electric field measurements were made using silver chloride electrodes at various points in the stimulated solution. This allowed the mapping of the electric potentials. The empirical data compared favorably to the results of the FEM thus validating in the method and assumptions. Finite element modeling provides an accurate method to visualize the electrical current densities resulting from bipolar stimulation. The FEM can now be used to determine the optimal electrode configuration for TES and other electrical stimulation protocols. This computer modeling method will ultimately lead improved patient results.
治疗性电刺激（TES）是一种针对神经肌肉疾病患者的康复刺激疗法。TES使用阈下经皮电刺激，通过增加血流量来促进肌肉生长和神经元发芽。为了优化TES疗法，需要一种新方法来确定目标肌肉中的电流密度。这是因为TES的阈下刺激强度不会产生任何可测量的生理效应。有限元法（FEM）是所选用的数值建模方法。FEM能够对生物体内发现的复杂特性进行建模，例如不同的组织类型和各向异性的组织特性。TES使用35Hz的双相波形。在这个低频下，采用了准静态近似。这使得可以用热传递模型解来找到稳态电场解。本文的目的是表明热传递结果与在生物模型中进行的电场测量结果相同。在一个装有生理盐水的一升圆柱体中使用双极刺激进行实验室测量。在受刺激溶液的不同点使用氯化银电极进行电场测量。这使得能够绘制电势图。实验数据与有限元法的结果相比非常有利，从而验证了该方法和假设。有限元建模提供了一种准确的方法来可视化双极刺激产生的电流密度。现在可以使用有限元法来确定TES和其他电刺激方案的最佳电极配置。这种计算机建模方法最终将带来更好的患者治疗效果。
