Modeling Current Sources for Neural Stimulation in COMSOL.
Modeling Current Sources for Neural Stimulation in COMSOL.
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DOI：
10.3389/fncom.2018.00040
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发表时间：
2018
影响因子：
3.2
通讯作者：
Grill WM
中科院分区：
文献类型：
--
作者：
Pelot NA;Thio BJ;Grill WM
背景：计算模型为设计和分析用于治疗神经系统疾病的神经刺激装置提供了重要的工具集。建模可以有效地探索大参数空间，而临床前和临床研究在这些空间中是不可行的。当前的商业有限元方法软件包可以直接计算电位分布，但并不总是清楚如何实现边界条件来适当地表示金属刺激电极。通过量化不同电极表示对模型轴突激活阈值的影响，我们为准确有效的神经刺激电极建模提供建议。方法：我们在 COMSOL Multiphysics 中量化了不同表示形式的电流源对单极、双极和多极电极设计的神经刺激的影响。结果：我们建议将每个电极接触点建模为薄铂域，使用硅树脂的导电性对电极基底进行建模，并在每个电极接触点的中心使用点电流源或使用边界电流源。或者，为了避免与大范围电导率值（即铂和硅树脂）相关的可能的数值不稳定性，并消除薄电极触点所需的小网格元素，可以通过在基板和周围介质之间以及在基板内使用绝缘边界来将电极基板指定为铂的电导率，以将触点彼此隔离。当对多个接触进行建模时，我们建议使用叠加，方法是为每个接触求解一次模型，使不活动的接触保持浮动，然后叠加产生的电势。我们计算了简化模型（均匀各向同性介质中的电极）以及大鼠脊髓刺激（SCS）和人类深部脑刺激的现实模型中不同实现的激活阈值的可比较误差，表明推荐的方法适用于不同的刺激目标。
Background: Computational modeling provides an important toolset for designing and analyzing neural stimulation devices to treat neurological disorders and diseases. Modeling enables efficient exploration of large parameter spaces, where preclinical and clinical studies would be infeasible. Current commercial finite element method software packages enable straightforward calculation of the potential distributions, but it is not always clear how to implement boundary conditions to appropriately represent metal stimulating electrodes. By quantifying the effects of different electrode representations on activation thresholds for model axons, we provide recommendations for accurate and efficient modeling of neural stimulating electrodes. Methods: We quantified the effects of different representations of current sources for neural stimulation in COMSOL Multiphysics for monopolar, bipolar, and multipolar electrode designs. Results: We recommend modeling each electrode contact as a thin platinum domain, modeling the electrode substrate with the conductivity of silicone, and either using a point current source in the center of each electrode contact or using a boundary current source. Alternatively, to avoid possible numerical instabilities associated with a large range of conductivity values (i.e., platinum and silicone) and to eliminate the small mesh elements required for thin electrode contacts, the electrode substrate can be assigned the conductivity of platinum by using insulating boundaries between the substrate and surrounding medium, and within the substrate to isolate the contacts from each other. When modeling more than one contact, we recommend using superposition by solving the model once for each contact, leaving inactive contacts floating, and superposing the resulting potentials. We computed comparable errors in activation thresholds across the different implementations in a simplified model (electrode in a homogeneous, isotropic medium), and in realistic models of rat spinal cord stimulation (SCS) and human deep brain stimulation, indicating that the recommended approaches are applicable to different stimulation targets.
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