Deurloo K E, Holsheimer J, Boom H B
Department of Electrical Engineering, University of Twente, Enschede, The Netherlands.
Med Biol Eng Comput. 1998 Jan;36(1):66-74. doi: 10.1007/BF02522860.
Various anode-cathode configurations in a nerve cuff are modelled to predict their spatial selectivity characteristics for functional nerve stimulation. A 3D volume conductor model of a monofascicular nerve is used for the computation of stimulation-induced field potentials, whereas a cable model of myelinated nerve fibre is used for the calculation of the excitation thresholds of fibres. As well as the usual configurations (monopole, bipole, longitudinal tripole, 'steering' anode), a transverse tripolar configuration (central cathode) is examined. It is found that the transverse tripole is the only configuration giving convex recruitment contours and therefore maximises activation selectivity for a small (cylindrical) bundle of fibres in the periphery of a monofascicular nerve trunk. As the electrode configuration is changed to achieve greater selectivity, the threshold current increases. Therefore threshold currents for fibre excitation with a transverse tripole are relatively high. Inverse recruitment is less extreme than for the other configurations. The influences of several geometrical parameters and model conductivities of the transverse tripole on selectivity and threshold current are analysed. In chronic implantation, when electrodes are encapsulated by a layer of fibrous tissue, threshold currents are low, whereas the shape of the recruitment contours in transverse tripolar stimulation does not change.
对神经袖套中的各种阳极 - 阴极配置进行建模，以预测其在功能性神经刺激方面的空间选择性特征。使用单束神经的三维容积导体模型来计算刺激诱发的场电位，而使用有髓神经纤维的电缆模型来计算纤维的兴奋阈值。除了通常的配置（单极、双极、纵向三极、“导向”阳极）外，还研究了横向三极配置（中央阴极）。研究发现，横向三极是唯一能给出凸形募集轮廓的配置，因此对于单束神经干外围一小束（圆柱形）纤维的激活选择性最大化。随着电极配置的改变以实现更高的选择性，阈值电流会增加。因此，横向三极刺激纤维兴奋的阈值电流相对较高。反向募集比其他配置的情况要轻。分析了横向三极的几个几何参数和模型电导率对选择性和阈值电流的影响。在长期植入时，当电极被一层纤维组织包裹时，阈值电流较低，而横向三极刺激中募集轮廓的形状不变。
