# Cancer Treatment: An Overview of Pulsed Electric Field Utilization and Generation
## 3 Tumour Treating Field and Electroporation Process  
Electroporation is an indication of electric pore formation, which involves increasing the permeability of the cell membrane by applying PEF to biological cells or tissues [7]. It is important to properly select the voltage pulse and electrode parameters, as listed in Table 2.  
By exposing the cell to such a field, one of two scenarios results:  
* In reversible electroporation (RE), temporary pores are formed and the cell reseals after a period of time and survives. This method facilitates drug delivery by increasing cell permeability, and can be useful for modifying or inserting DNA and other molecules into cells. * In irreversible electroporation (IRE), the pulse parameters exceed a certain level based on the delivered pulses that prevents the cell from resealing. This can cause permanent damage in the form of pores, eventually leading to apoptosis. The breakdown of cells depends on many parameters including the ambient temperature, pulse duration, and cell charging time constant. By varying the pulse properties, a potentially infinite number of applications can be targeted based on project requirements. Different applications of electroporation based on low-voltage long pulses, high-voltage short pulses, and synergetic pulses achieved by mixing both long and short pulses are shown in Figure 2 and summarized in Table 3. Cancer electrochemotherapy utilizes RE \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**Characteristics** & **Benign Tumours** & **Malignant Tumours** \\ \hline Cell growth & Grow slowly & Grow quickly \\ Shape & Have distinct borders & Have irregular borders \\ Effect on nearby tissues & Do not invade surrounding tissues & Invade surrounding tissues \\ Spread & Do not invade other parts of the body & Can spread to other parts of the body \\ \hline \multirow{2}{*}{Treatment} & Require invasive surgical removal if the tumour & \\ leads to blockage or compression of nearby & One or a combination of these modalities: surgery, radiotherapy, chemotherapy, immunotherapy \\  & structures, or if it becomes malignant & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Benign tumours vs. malignant tumours [23; 26]. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**Pulse Parameters** & **Electrode Parameters** \\ \hline Waveform & \\ Peak & Shape \\ Polarity & Separation distance \\ Duration & Alignment angle of electrodes \\ Rise and fall time & \\ Total number of pulses & \\ Repetition rate & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: System parameters for pulses and electrodes. to initiate pores and allow drugs to enter the cells; the pores then reseal after a period of time [27]. Cancer treatment methods based on the utilization of IRE to cause permanent damage to tumour cells have been reviewed in [7,27]. In another context, PEF is used in food processing to kill bacteria in order to preserve food for long periods of time with reduced need for chemical food preservatives [28]. There are many pulse waveforms that solid-state-based PG can generate if the electroporator is based on multilevel techniques [29]. These pulse waveforms are rectangular, exponential, and multipulse. The most utilized technique for food processing is the application of multipulse waveforms, which reduces amount of heat generated in order to maintain the nutritional value of food [30]. Electroporation has additionally been used as an emerging technology to enhance the extraction of juice from various types of fruits, as well as other plants such as olives and sugar beets [28]. Cells have many charged and polarisable molecules inside them on which TTF can exert biophysical forces to obtain a spectrum of biological effects. It was initially thought that the mitotic apparatus was the only mechanism by which TTF interfered with cancer cells to inhibit proliferation; however, recent research has described other effective TTF mechanisms on cancer cells [19].