Magnetic resonance electrical impedance tomography (MREIT) was recently proposed for determining electric field distribution during electroporation in which cell membrane permeability is temporary increased by application of an external high electric field. The method was already successfully applied for reconstruction of electric field distribution in agar phantoms. Before next step towards in vivo experiments is taken, monitoring of electric field distribution during electroporation of ex vivo tissue and feasibility for its use in electroporation based treatments need to be evaluated. Sequences of high voltage pulses were applied to chicken liver tissue in order to expose it to electric field which was measured by means of MREIT. MREIT was also evaluated for its use in electroporation based treatments by calculating electric field distribution for two regions, the tumor and the tumor-liver region, in a numerical model based on data obtained from clinical study on electrochemotherapy treatment of deep-seated tumors. Electric field distribution inside tissue was successfully measured ex vivo using MREIT and significant changes of tissue electrical conductivity were observed in the region where electric field was the highest. A good agreement was obtained between the electric field distribution obtained by MREIT and the true electric field distribution in both evaluated regions of a numerical model, suggesting that implementation of MREIT could thus enable efficient detection of areas with insufficient electric field coverage during electroporation based treatments, thus assuring the effectiveness of the treatment.
COBISS.SI-ID: 9398868
Electrochemotherapy uses electroporation for enhancing chemotherapy. Electrochemotherapy can be performed using standard operating procedures with predefined electrode geometries, or using patient-specific treatment planning to predict electroporation. The latter relies on realistic computer models to provide optimal results (i.e. electric field distribution as well as electrodes' position and number) and is suitable for treatment of deep-seated tumors. Since treatment planning for deep-seated tumors has been used in radiotherapy, we expose parallelisms with radiotherapy in order to establish the procedure for electrochemotherapy of deep-seated tumors. We partitioned electrochemotherapy in the following phases: the mathematical model of electroporation, treatment planning, set-up verification, treatment delivery and monitoring, and response assessment. We developed a conceptual treatment planning software that incorporates mathematical models of electroporation. Preprocessing and segmentation of the patient's medical images are performed, and a 3D model is constructed which allows placement of electrodes and implementation of the mathematical model of electroporation. We demonstrated the feasibility of electrochemotherapy of deep-seated tumors treatment planning within a clinical study where treatment planning contributed to the effective electrochemotherapy treatment of deep-seated colorectal metastases in the liver. The described procedure can provide medical practitioners with information on using electrochemotherapy in the clinical setting.
COBISS.SI-ID: 9338452
Induction heating equipment is a source of strong and nonhomogeneous magnetic fields, which can exceed occupational reference levels. We investigated a case of an induction tempering tunnel furnace. Measurements of the emitted magnetic flux density (B) were performed during its operation and used to validate a numerical model of the furnace. This model was used to compute the values of B and the induced in situ electric field (E) for 15 different body positions relative to the source. For each body position, the computed B values were used to determine their maximum and average values, which were then compared to the ICNIRP reference level, and E values to the ICNIRP basic restriction. Our results show that in nonhomogeneous fields, the maximum B is an overly conservative predictor of overexposure, as it yields many false positives. The average B yielded fewer false positives, but as the number of averaging points increased, false negatives emerged. The most reliable averaging schemes were obtained for averaging over the torso with quadratic averaging, with no false negatives even for the maximum number of averaging points investigated.
COBISS.SI-ID: 9356372
We outline the need and offer a solution in medical education in the field of electroporation-based treatments, e.g. primarily electrochemotherapy and non-thermal irreversible tissue ablation. We present the background, the means of implementation and the fully functional application, which is the first of its kind. The application allows for visualization and analysis of electric field strength in multiple electrode electroporation. The initial feedback from students that have evaluated this application as part of an e-learning course was positive, and a formal study is planned to thoroughly evaluate the current version and identify possible future improvements and modifications.
COBISS.SI-ID: 9515092
We describe the development and testing of a setup that allows for dielectrophoretic field-flow fractionation (DEP-FFF) of irreversibly electroporated, reversibly electroporated, and nonelectroporated cells based on their different polarizabilities. We first optimized the channel and electrode dimensions, flow rate, and electric field parameters for efficient DEP-FFF separation of moderately heat-treated CHO cells (50°C for 15 min) from untreated ones, with the former used as a uniform and stable model of electroporated cells. We then used CHO cells exposed to electric field pulses with amplitudes from 1200 to 2800 V/cm, yielding six groups containing various fractions of nonporated, reversibly porated, and irreversibly porated cells, testing their fractionation in the chamber. DEP-FFF at 65 kHz resulted in distinctive flow rates for nonporated and each of the porated cell samples groups. At lower frequencies the efficiency of fractionation deteriorated, while at higher frequencies the separation of individual elution profiles was further improved, but at the cost of cell flow rate slowdown in all samples the cell groups, implying undesired transition from negative into positive DEP, where the cells are pulled towards the electrodes. Our results demonstrate that fractionation of irreversibly electroporated, reversibly electroporated, and nonelectroporated cells is feasible at a properly selected frequency.
COBISS.SI-ID: 9359444