Sel Davorka, Lebar Alenka Macek, Miklavcic Damijan
University of Ljubljana, Faculty of Electrical Engineering, Trakya 25, SI-1000 Ljubljana, Slovenia.
IEEE Trans Biomed Eng. 2007 May;54(5):773-81. doi: 10.1109/TBME.2006.889196.
In electrochemotherapy (ECT) electropermeabilization, parameters (pulse amplitude, electrode setup) need to be customized in order to expose the whole tumor to electric field intensities above permeabilizing threshold to achieve effective ECT. In this paper, we present a model-based optimization approach toward determination of optimal electropermeabilization parameters for effective ECT. The optimization is carried out by minimizing the difference between the permeabilization threshold and electric field intensities computed by finite element model in selected points of tumor. We examined the feasibility of model-based optimization of electropermeabilization parameters on a model geometry generated from computer tomography images, representing brain tissue with tumor. Continuous parameter subject to optimization was pulse amplitude. The distance between electrode pairs was optimized as a discrete parameter. Optimization also considered the pulse generator constraints on voltage and current. During optimization the two constraints were reached preventing the exposure of the entire volume of the tumor to electric field intensities above permeabilizing threshold. However, despite the fact that with the particular needle array holder and pulse generator the entire volume of the tumor was not permeabilized, the maximal extent of permeabilization for the particular case (electrodes, tissue) was determined with the proposed approach. Model-based optimization approach could also be used for electro-gene transfer, where electric field intensities should be distributed between permeabilizing threshold and irreversible threshold-the latter causing tissue necrosis. This can be obtained by adding constraints on maximum electric field intensity in optimization procedure.
在电化学疗法（ECT）的电穿孔过程中，需要对参数（脉冲幅度、电极设置）进行定制，以便使整个肿瘤暴露于高于通透阈值的电场强度下，从而实现有效的ECT。在本文中，我们提出了一种基于模型的优化方法，用于确定有效ECT的最佳电穿孔参数。通过最小化肿瘤选定部位的通透阈值与有限元模型计算出的电场强度之间的差异来进行优化。我们在由计算机断层扫描图像生成的模型几何结构上检验了基于模型的电穿孔参数优化的可行性，该模型几何结构代表带有肿瘤的脑组织。待优化的连续参数是脉冲幅度。电极对之间的距离作为离散参数进行优化。优化还考虑了脉冲发生器对电压和电流的限制。在优化过程中，达到了两个限制条件，阻止了肿瘤的整个体积暴露于高于通透阈值的电场强度下。然而，尽管使用特定的针阵列支架和脉冲发生器时肿瘤的整个体积未被通透，但通过所提出的方法确定了特定情况（电极、组织）下的最大通透范围。基于模型的优化方法也可用于电基因转移，其中电场强度应分布在通透阈值和不可逆阈值之间——后者会导致组织坏死。这可以通过在优化过程中添加对最大电场强度的限制来实现。
