Incorporation of the Blood Vessel Wall into Electroporation Simulations

Abstract

Electroporation can be used in living tissues in order to enhance the penetration of drugs or DNA plasmids or to destroy undesirable cells and it is typically performed by applying pulsed high voltages across needle electrodes. When used for ablation, it is often claimed that, in contrast with thermal ablation techniques, electroporation is not significantly impacted by the presence of large blood vessels because the heat sinking characteristic of these is not relevant for the electric field distribution. However, large blood vessels do distort the electric field distribution because of their high inner conductivity and should be modeled during treatment planning. For such purpose, vessels may be simply modeled as homogeneous regions whose conductivity is equal to that of the blood. Nevertheless, vessels are not just blood filled cavities within parenchyma; blood vessels contain a layered wall. The purpose of the present study is to check whether the blood vessel wall needs to be incorporated into the simulations. For that, a vessel wall electrical model has been implemented and it has been incorporated into 2D and 3D simulations in which treatment of a region that comprises a 5 mm thick artery within liver was modeled. The three main layers of a vessel wall (the intima, the media and the adventitia) were modeled as homogeneous materials whose conductivity depends on the electric field magnitude. The simulations show that the electric field error when the wall model is not incorporated is only marginally significant at the close vicinity of the vessel for low applied fields. Errors are insignificant beyond 1 or 2 mm. We conclude that in most electroporation scenarios it will not be necessary to simulate the blood vessel wall.

Anatomically Realistic Simulations of Liver Ablation by Irreversible Electroporation: Impact of Blood Vessels on Ablation Volumes and Undertreatment

“…However, to validate this simplification, an additional group of simulations was repeated with the inclusion of a 1-mm vessel wall around large hepatic veins and portal vein, as described in our previous study. 30 The results of these simulations is included in the supplemental materials ( Figure 1 and Table 7 ). The results show that the presence of the wall reduces the influence of blood on the electric field distribution and the undertreatment volumes.…”

A computational comparison of radiofrequency and pulsed field ablation in terms of lesion morphology in the cardiac chamber

“…Within the heart tissue, the governing equation for solving the thermal problem was based on the Penne’s Bioheat equation that was solved using the Heat Transfer module in COMSOL Multiphysics: where is the density (kg/m 3 ), is the heat capacity (J/kg·K), i = l represents the liquid phase and i = v the vapor phase parameters of the biological tissue, is the temperature (K), is the time (s), is the coefficient of heat conductivity (W/m·K), is the heat source by Joule heating caused by RF energy (W/m 3 ) which is proportional to the electrical conductivity and to the square of the electric field magnitude (V/m), , is the heat loss caused by blood perfusion (W/m 3 ) and is the metabolic heat generation (W/m 3 ). was not considered since it has been demonstrated computationally and experimentally that the blood flowing away in the coronary arteries of the heart tissue does not have significant influence on temperature distribution during radiofrequency ablation in cardiac tissue 47 . For PFA, the same assumption was considered.…”