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Available from: Matej Rebersek, Sep 03, 2014
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    • "6(b)]. It was shown, that out of several theoretical equations proposed for the description of such a relationship, the best fit to the experimental data was given by (1)–(4) [25]. In Fig. 6(c), the dependences of the amplitude of a squarewave electric pulse required to electroporate 50% of cells, E 0.5 , on the pulse duration are presented for human erythrocytes [18], [26], CHO [26], and mouse hepatoma MH-22A cells. "
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    ABSTRACT: Here, theoretical relationships between the parameters of the electric pulse, which is necessary to porate the cell by electric pulse of various shapes, have been obtained. The theoretical curves were compared with the experimental relationships. Experiments were carried out with human erythrocytes and mouse hepatoma MH-22A cells. The fraction of electroporated MH-22A cells was determined from the extent of the release of intracellular potassium ions and erythrocytes – from the extent of their hemolysis after long (20–24 h) incubation in 0.63% NaCl solution at 4 oC. The dependence of the fraction of electroporated cells on the amplitude of the electric field pulse was determined for pulses with the duration from 95 ns to 2 ms. The shapes of theoretical dependencies are in agreement with experimental ones. The cell poration time depended on the intensity of the pulse: the shorter the pulse duration, the higher the electric field strength has to be. This dependence is much more pronounced for pulses shorter than 1 μs. For example, if the pulse amplitude required to electroporate 50% of human erythrocytes increased from 1.0 to 1.76 kV/cm, when the duration of a square-wave pulse was reduced from 2 ms to 20 μs, it increased from 3 to 12 kV/cm, when the pulse duration was reduced from 950 to 95 ns. The relationships between the electric field strength required for electroporation and the frequency of the applied ac field were calculated for different pulse lengths. It has been obtained that although the electric field strength is constant for frequencies less than 10 kHz but its value depends on the pulse length decreasing with increasing pulse duration. At higher frequencies electric field strength is dependent on the frequency of the ac field.
    IEEE Transactions on Plasma Science 10/2013; 41(10):2913-2919. DOI:10.1109/TPS.2013.2276918 · 0.95 Impact Factor
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    ABSTRACT: Background Electrochemotherapy is a local treatment that utilizes electric pulses in order to achieve local increase in cytotoxicity of some anticancer drugs. The success of this treatment is highly dependent on parameters such as tissue electrical properties, applied voltages and spatial relations in placement of electrodes that are used to establish a cell-permeabilizing electric field in target tissue. Non-thermal irreversible electroporation techniques for ablation of tissue depend similarly on these parameters. In the treatment planning stage, if oversimplified approximations for evaluation of electric field are used, such as U/d (voltage-to-distance ratio), sufficient field strength may not be reached within the entire target (tumor) area, potentially resulting in treatment failure. Results In order to provide an aid in education of medical personnel performing electrochemotherapy and non-thermal irreversible electroporation for tissue ablation, assist in visualizing the electric field in needle electrode electroporation and the effects of changes in electrode placement, an application has been developed both as a desktop- and a web-based solution. It enables users to position up to twelve electrodes in a plane of adjustable dimensions representing a two-dimensional slice of tissue. By means of manipulation of electrode placement, i.e. repositioning, and the changes in electrical parameters, the users interact with the system and observe the resulting electrical field strength established by the inserted electrodes in real time. The field strength is calculated and visualized online and instantaneously reflects the desired changes, dramatically improving the user friendliness and educational value, especially compared to approaches utilizing general-purpose numerical modeling software, such as finite element modeling packages. Conclusion In this paper 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. While the initial feedback from students that have evaluated this application as part of an e-learning course is positive, a formal study is planned to thoroughly evaluate the current version and identify possible future improvements and modifications.
    BMC Medical Education 10/2012; 12(1):102. DOI:10.1186/1472-6920-12-102 · 1.41 Impact Factor
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    ABSTRACT: 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 the next step towards in vivo experiments is taken, monitoring of electric field distribution during electroporation of ex vivo tissue ex vivo and feasibility for its use in electroporation based treatments needed 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 of the highest electric field. A good agreement was obtained between the electric field distribution obtained by MREIT and the actual electric field distribution in 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.
    PLoS ONE 09/2012; 7(9):e45737. DOI:10.1371/journal.pone.0045737 · 3.53 Impact Factor
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