Ablation outcome of irreversible electroporation on potato monitored by impedance spectrum under multi-electrode system

Abstract

BackgroundIrreversible electroporation (IRE) therapy relies on pulsed electric fields to non-thermally ablate cancerous tissue. Methods for evaluating IRE ablation in situ are critical to assessing treatment outcome. Analyzing changes in tissue impedance caused by electroporation has been proposed as a method for quantifying IRE ablation. In this paper, we assess the hypothesis that irreversible electroporation ablation outcome can be monitored using the impedance change measured by the electrode pairs not in use, getting more information about the ablation size in different directions.MethodsUsing a square four-electrode configuration, the two diagonal electrodes were used to electroporate potato tissue. Next, the impedance changes, before and after treatment, were measured from different electrode pairs and the impedance information was extracted by fitting the data to an equivalent circuit model. Finally, we correlated the change of impedance from various electrode pairs to the ablation geometry through the use of fitted functions; then these functions were used to predict the ablation size and compared to the numerical simulation results.ResultsThe change in impedance from the electrodes used to apply pulses is larger and has higher deviation than the other electrode pairs. The ablation size and the change in resistance in the circuit model correlate with various linear functions. The coefficients of determination for the three functions are 0.8121, 0.8188 and 0.8691, respectively, showing satisfactory agreement. The functions can well predict the ablation size under different pulse numbers, and in some directions it did even better than the numerical simulation method, which used different electric field thresholds for different pulse numbers.ConclusionsThe relative change in tissue impedance measured from the non-energized electrodes can be used to assess ablation size during treatment with IRE according to linear functions.

Design and Characterization of a Minimally Invasive Bipolar Electrode for Electroporation

“…(Aquila, Abbruzzo, Italy) are used in this study. The pre-clinical study on a vegetable model has been performed on potatoes, thanks to their produced electric field which is very similar to that observed in both animal and humans organs/tissues [5,35]. In each test, the electrode was inserted into the potato for all its length, making sure that the conductive part was at least 10 mm deep inside.…”

“…When cells are exposed to intense pulsed electric fields of at least 400 V/cm as local value [1][2][3], the permeability and conductivity of their membranes increase, allowing local electric field spreading in the cells and their surroundings. The pores on the cells' membrane permit the entry of substances that otherwise could not enter the cytoplasm [1][2][3][4][5]. As is known, it is possible to use different electroporation parameters (number and voltage amplitude of pulses) in order to obtain a reversible or irreversible effect on the electroporated cells' membranes.…”

Physiological changes may dominate the electrical properties of liver during reversible electroporation: Measurements and modelling

“…In an ideal system composed by two infinite parallel plates and neglecting any electrode polarization effect, the impedance evolution with respect to the applied voltage would perfectly follow the sigmoid function described in Eq. (4), ( 5) or (6). However, due to the four-electrode topology where a current is injected through the external needles and the voltage is measured between the internal needles, the inhomogeneous conductivity distribution may affect the impedance changes in a non-intuitive way.…”

“…In fundamental studies, electrical measurements could reveal the pore dynamics (formation, expansion, shrinkage) [2]. On the other hand, there is an ongoing technological research to develop electrical measurement tools to provide real-time feedback control systems for treatments based on electroporation, for instance to prevent, or optimize irreversible electroporation (IRE) [3][4][5][6].…”

Development of a Multi-Pulse Conductivity Model for Liver Tissue Treated With Pulsed Electric Fields

“…Therapeutic efficacy in either of these therapies is dependent on adequate coverage of the target area with electric fields capable of inducing electroporation; thus, clinicians are in need of tools capable of providing information regarding ablation outcome. In addition to post-treatment imaging using ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) (Onik and Rubinsky, 2010;Sommer et al, 2013;Ting et al, 2016), real-time evaluation of the ablation outcome has been proposed in recent studies (Ivorra et al, 2009;Zhao et al, 2018b). Pretreatment visualization of the expected treatment zone also aids in achieving complete ablation (Edd and Davalos, 2007).…”