Helical Open Waveguide Structure for Optimization of Microwave Ablation

The subject of this paper concerns the design and optimization of a helical open waveguide structure for thermal tumor ablation with microwaves, a treatment also known as MicroWave Ablation (MWA). A variety of antennas for MWA have been developed so far. However, most of these antennas cannot accurately control the temperature field they produce. As a result, the heating extends to healthy tissues as well. Therefore, the first innovation proposed here is to use a helical open waveguide structure that will control the distribution of the deposited electromagnetic power and achieve the total destruction of the tumor, with less damage to the surrounding healthy tissue ('healthy tissue sparing'). By changing the distance of the spirals of the helix, we are able to limit the field to the dimensions of the cancerous tumor. An antenna for MWA is usually designed for specific physical and geometrical parameters of the problem which determine its input impedance, resonant frequency and operating bandwidth. However, a MWA antenna should be able to be used within different tissues. The second innovation of the present research proposal is the construction of an open helical waveguide structure, which can adapt to the complex load presented by the tissue where the waveguide enters. This will be achieved, on the one hand with the dimensions of the helix spirals which will be changed by rotary motion, and on the other hand with a transformer made of coaxial cable preceding the waveguide. Finally, a parametric analysis of the construction is performed by changing the number and height of the spirals to see which structure produces the best results (more uniform temperature distribution with less damage to the surrounding tissue) but also by changing the length of its monopole.