A numerical study on the effect of conductivity change in cell kill distribution in irreversible electroporation

In silico study about the influence of electroporation parameters on the cellular internalization, spatial uniformity, and cytotoxic effects of chemotherapeutic drugs using the Method of Fundamental Solutions

Reversible electroporation is a suitable technique to aid the internalization of medicaments in cancer tissues without inducing permanent cellular damage, allowing the enhancement of cytotoxic effects without incurring in electric-driven necrotic or apoptotic processes by the presence of non-reversible aqueous pores. An adequate selection of electroporation parameters acquires relevance to reach these goals and avoid opposite effects. This work applies the Method of Fundamental Solutions (MFS) for drug transport simulations in electroporated cancer tissues, using a continuum tumor cord approach and considering both electro-permeabilization and vasoconstriction effects. The MFS algorithm is validated with published results, obtaining satisfactory accuracy and convergence. Then, MFS simulations are executed to study the influence of electric field magnitude [Formula: see text], number of electroporation treatments [Formula: see text], and electroporation time [Formula: see text] on three assessment parameters of electrochemotherapy: the internationalization efficacy accounting for the ability of the therapy to introduce moles into viable cells, cell-kill capacity indicating the faculty to reduce the survival fraction of cancer cells, and distribution uniformity specifying the competence to supply drug homogeneously through the whole tissue domain. According to numerical results, when [Formula: see text] is the reversibility threshold, a positive influence on the first two parameters is only possible once specific values of [Formula: see text] and [Formula: see text] have been exceeded; when [Formula: see text] is just the irreversibility threshold, any combination of [Formula: see text] and [Formula: see text] is beneficial. On the other hand, the drug distribution uniformity is always adversely affected by the application of electric pulses, being this more noticeable as [Formula: see text], [Formula: see text], and [Formula: see text] increases.

Thermal damage map prediction during irreversible electroporation with U-Net

Recent developments in cancer treatment with irreversible electroporation (IRE) have led to a renewed interest in developing a treatment planning system based on Deep-Learning methods. This paper will give an account of U-Net, as a Deep-Learning architecture usage for predicting thermal damage area during IRE. In this study, an irregular shape of the liver tumor with MIMICS and 3-Matic software was created from Magnetic Resonance Imaging (MRI) images. To create electric field distribution and thermal damage maps in IRE, COMSOL Multiphysics 5.3 finite element analysis was performed. It was decided to use the pair needle, single bipolar, and multi-tine electrodes with different geometrical parameters as electrodes. The U-Net was designed as a Deep-Learning network to train and predict the thermal damage area from electric field distribution in the IRE. The average DICE coefficient and accuracy of trained U-Net for predicting thermal damage area on test data sets were 0.96 and 0.98, respectively, for the dataset consisting of all electrode type electric field intensity images. This is the first time that U-Net has been used to predict thermal damage area. The results of this research support the idea that the U-Net can be used for predicting thermal damage areas during IRE as a treatment planning system.

Influence of electric field, blood velocity, and pharmacokinetics on electrochemotherapy efficiency

The convective delivery of chemotherapeutic drugs in cancerous tissues is directly proportional to the blood perfusion rate, which in turns can be transiently reduced by the application of high-voltage and short-duration electric pulses due to vessel vasoconstriction. However, electric pulses can also increase vessel wall and cell membrane permeabilities, boosting the extravasation and cell internalization of drug. These opposite effects, as well as possible adverse impacts on the viability of tissues and endothelial cells, suggest the importance of conducting in silico studies about the influence of physical parameters involved in electric-mediated drug transport. In the present work, the global method of approximate particular solutions for axisymmetric domains, together with two solution schemes (Gauss-Seidel iterative and linearization+successive over-relaxation), is applied for the simulation of drug transport in electroporated cancer tissues, using a continuum tumor cord approach and considering both the electropermeabilization and vasoconstriction phenomena. The developed global method of approximate particular solutions algorithm is validated with numerical and experimental results previously published, obtaining a satisfactory accuracy and convergence. Then, a parametric study about the influence of electric field magnitude and inlet blood velocity on the internalization efficacy, drug distribution uniformity, and cell-kill capacity of the treatment, as expressed by the number of internalized moles into viable cells, homogeneity of exposure to bound intracellular drug, and cell survival fraction, respectively, is analyzed for three pharmacokinetic profiles, namely one-short tri-exponential, mono-exponential, and uniform. According to numerical results, the trade-off between vasoconstriction and electropermeabilization effects and, consequently, the influence of electric field magnitude and inlet blood velocity on the assessment parameters considered here (efficacy, uniformity, and cell-kill capacity) is different for each pharmacokinetic profile deemed.

Influence of electric pulse characteristics on the cellular internalization of chemotherapeutic drugs and cell survival fraction in electroporated and vasoconstricted cancer tissues using boundary element techniques

Electroporation has emerged as a suitable technique to induce the pore formation in the cell membrane of cancer tissues, facilitating the cellular internalization of chemotherapeutic drugs. An adequate selection of the electric pulse characteristics is crucial to guarantee the efficiency of this technique, minimizing the adverse effects. In the present work, the dual reciprocity boundary element method (DR-BEM) is applied for the simulation of drug transport in the extracellular and intracellular space of cancer tissues subjected to the application of controlled electric pulses, using a continuum tumour cord approach, and considering both the electro-permeabilization and vasoconstriction phenomena. The developed DR-BEM algorithm is validated with numerical and experimental results previously published, obtaining a satisfactory accuracy and convergence. Using the DR-BEM code, a study about the influence of the magnitude of electric field (E) and pulse spacing (dpulses) on the time behavior and spatial distribution of the internalized drug, as well as on the cell survival fraction, is carried out. In general, the change of drug concentration, drug exposure and cell survival fraction with the parameters E and dpulses is ruled by two important factors: the balance between the electro-permeabilization and vasoconstriction phenomena, and the relative importance of the sources of cell death (electric pulses and drug cytotoxicity); these two factors, in turn, significantly depend on the reversible and irreversible thresholds considered for the electric field.

Automated irreversible electroporated region prediction using deep neural network, a preliminary study for treatment planning

The primary purpose of cancer treatment with irreversible electroporation (IRE) is to maximize tumor damage and minimize surrounding healthy tissue damage. Finite element analysis is one of the popular ways to calculate electric field and cell kill probability in IRE. However, this method also has limitations. This paper will focus on using a deep neural network (DNN) in IRE to predict irreversible electroporated regions for treatment planning purposes. COMSOL Multiphysics was used to simulate the IRE. The electric conductivity change during IRE was considered to create accurate data sets of electric field distribution and cell kill probability distributions. We used eight pulses with a pulse width of 100 μs, frequency of 1 Hz, and different voltages. To create masks for DNN training, a 90% cell kill probability contour was used. After data set creation, U-Net architecture was trained to predict irreversible electroporated regions. In this study, the average U-Net DICE coefficient on test data was 0.96. Also, the average accuracy of U-Net for predicting irreversible electroporated regions was 0.97. As far as we are aware, this is the first time that U-Net was used to predict an irreversible electroporated region in IRE. The present study provides significant evidence for U-Net's use for predicting an irreversible electroporated region in treatment planning.

Investigating the effect of electrode orientation on irreversible electroporation with experiment and simulation

PURPOSE

In recent years, irreversible electroporation (IRE) has been developed to specifically destroy undesirable tissues as an alternative to surgical resection. In this treatment, placing multiple electrodes in parallel is required to create a uniform electric field distribution. The process of maintaining parallel electrodes is challenging, and the effect of the electrodes' orientation accuracy has not been investigated quantitatively. This study investigates the impact of the electrode orientation along with various electrode and pulse parameters on the outcomes of IRE.

METHODS

The electrode configurations that were considered were parallel, forward, and sideward orientation. A numerical model was developed to study the effect of electrode orientation on the electric field distribution, which was validated experimentally on potato tubers as it has similar properties to biological tissue. In addition, a conductivity test was performed to evaluate the conductivity and electroporation threshold of the potatoes.

RESULTS

The developed numerical model was validated by comparing the electroporated volumes between potatoes from the experiment and simulation, which achieved a mean dice score of [Formula: see text]. The potato has an electrical conductivity of 0.044-0.454 S/m with an electroporation threshold of 375 V/cm. ANOVA test showed that the difference in the electroporated regions obtained between a parallel orientation and a 5[Formula: see text] forward and sideward orientation was not significant.

CONCLUSION

This study showed that the developed numerical models were validated and able to predict the outcome of IRE on potatoes. In addition, a 5[Formula: see text] tolerance on the electrode orientation can be defined to obtain a similar response to the parallel orientation.