# Microwave Ablation Theory

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CHAPTER TWO 2.0 Theoretical Framework Microwave ablation as a recently used treatment paradigm for cancer treatment it is also known to be one of the most promising development in today’s world especially in the field of tumor ablation. Practically, in clinical procedures the microwave generator releases the Electromagnetic waves from the opened slot of the antenna. The electromagnetic microwaves emitted will cause agitation of water molecules within the tissue which results to frictional heating and thereafter cause tissue death by a process call coagulation necrosis. (Caroline J. Simon M. e., 2005) Liver cancer as it implies, can be treated successfully through surgical procedures by removing the malignant tissues, about 90 percent of…show more content…
[13]The dielectric permittivity is larger and has real and imaginary parts used to define the relative permittivity and conductivity. (Crit Rev Biomed Eng. 2010.) Relative permittivity, εr, is the main part and it is the measure of the ability to absorb electrical energy relative to vacuum. It is frequently referred to as dielectric constant; however, permittivity depends on the frequency, temperature and others like biological tissues .[14] The effective conductivity, σ, of a material is denoted is used to describe how well the tissues will absorbs microwave energy. It is important to note that effective conductivity describes contributions from moving charges (electrical current) and time-varying electric fields (displacement current), specifically the rotation of dipoles in the material as they attempt to align with and alternating electric field.[11] The latter contribution dominates for most biological tissues in the microwave spectrum. (Crit Rev Biomed Eng.…show more content…
A magnetic field is applied across two electrodes (an anode and cathode). The anode has a cylindrical shape projecting inwards while the cathode take the shape of a pole at the center.When a potential is applied across the system the cathode heats emitting electrons. (Andrew David Strickland) These electrons are attracted to the positive anode and would pass in a straight line towards the anode except for the influence of the magnetic field. The magnetic field causes the electrons to be diverted taking an expanding circular orbit around the cathode eventually reaching the anode. It is this combined effect of the electric and magnetic field on the electrons emitted from the cathode that produces microwaves. Magnetrons produce microwaves at a fixed frequency and this frequency is related to the configuration of the cathode and anode. Altering the space between the anode and cathode changes the frequency of the microwaves