Simulation Study On Electroporation Ablation Zone Of Biological Tissue Under Micro-nanosecond Pulse

Irreversible electroporation,as a non-thermal tumor ablation technology,has been used in clinical practice.The newly proposed micro-nanosecond pulse can alleviate the muscle contraction and ablation blind spots in the target area caused by traditional irreversible electroporation pulses.As a physical ablation technology based on electroporation,it is usually necessary to determine its therapeutic range through numerical calculation in order to screen suitable pulse parameters and electrode configurations.The traditional numerical calculation models only considered the tissue electroporation effect and biological heat transfer effect to calculate the electric field distribution,and usually assumed that the tissue is isotropic.Due to high-frequency and serial application characteristics of micro-nanosecond pulses,the tissue dispersion effect and electroporation threshold change cannot be ignored.Based on the above problems,this thesis constructed a numerical calculation model including dispersion effect,anisotropic conductivity and the change of electroporation threshold to numerically study the tissue electroporation ablation area with the applying of micronanosecond pulse.The main conclusions are as follows:1.On the basis of traditional electroporation theory and biological heat transfer theory,a two-dimensional breast tumor tissue model was constructed under the two-needle electrode configuration,incorporating tissue dispersion model and anisotropic conductivity model.The ablation area of model was investigated with the applying of a single micro-nanosecond pulse with pulse width of 500 ns and amplitude of 4000 V.The results showed that in the anisotropic conductivity model considering the dispersion effect,the tissue electroporation area increased by 3.55%,the irreversible electroporation area decreased by 4.53%,and no thermal damage occurred inside the model.2.Based on the above simulation model,incorporating the change of electroporation threshold,a two-dimensional breast tumor tissue model was established under the configuration of two-needle electrodes.After applying 8 bursts with sub-pulse width of 500 ns and amplitude of 4000 V,the results showed that compared with the numerical results of the first pulse,the electroporation area increased by 22.91%,the irreversible electroporation area increased by 17.62%,and 8.28% of local tissues were irreversibly thermally damaged at the end of the burst,and the area of irreversible electroporation ablation cannot cover the entire tumor tissue under the two-needle electrode configuration.3.In order to avoid large-area thermal damage inside the tissue,six bursts with sub-pulse width of 2 μs and amplitude of 2900 V were applied to the simulation model,and the corresponding three-needle electrode configuration and the four-needle electrode configuration were constructed.The simulation results showed that with the increase of the number of electrode needles,the ablation area of irreversible electroporation continued to increase.The three-needle electrode ablation accounts for 83.58 %,and the four-needle electrode ablation accounts for 99.08 %,which can be defaulted as complete ablation of the tumor and no irreversible thermal damage occurred.In summary,this thesis analyzed the effects of dispersion effect,anisotropic conductivity and the change of electroporation threshold on the simulation results,and studied the multineedle electrode configuration to achieve complete tumor ablation.The above conclusions can provide certain theoretical guiding significance for the subsequent clinical electroporation ablation of tumor tissue.