Non-dimensional numerical simulation of tissue ablation and thermal damage in irreversible electroporation

Irreversible electroporation(IRE)is a technique to permanently perforate cell membrane by an application of intensive electric pulses. Since it is achieved via percutaneous electrodes, the IRE shows promise for a less-invasive and non-thermal treatment of tumor tissues. Treatment outcome is affected by various factors such as electrode configuration, physical properties of the targeted tissue, and pulse conditions. For a successful IRE, both ablated volume and unfavorable Joule heating attributed to the electric current must be predicted prior to the treatment depending on above factors. The aim of this study was, therefore, to demonstrate that the IRE parameters depending on the targeted volume could be determined by non-dimensional 3-D solutions to electric field and heat conduction. The Laplace equation and the heat conduction equation in non-dimensional forms were numerically solved using the finite element method for three analytical models with different electrode geometries. Although a number of previous studies have reported that numerical analysis was useful for the prediction of the IRE outcome, our study intended to show extensive usability of the non-dimensional analysis because of its high generality. The analyses provided a set of electric field and temperature distribution in nondimensional forms, which could be translated to the actual field intensity, ablated lengths, temperature rise, and probability of thermal damage, depending on arbitrary electrode diameter, electrode spacing, pulse voltage, and pulse time. Additionally, a case study with an assumption of IRE ablation for 5-mm diameter tumor was conducted, which demonstrated that the optimal electrode geometry and pulse parameters including input voltage as well as acceptable pulse duration to avoid thermal damage could be determined by a set of the results from non-dimensional analyses.