Conformal Array Antenna Design For Breast Cancer Microwave Hyperthermia

Nowadays,microwave hyperthermia,a process that involves heating tumour cells,has been proposed as an alternative method of treating breast cancer.By sending microwave energy of a suitable frequency range to the breast,localized heating is induced by the applied electromagnetic radiation.It is important to heat the tumor to a temperature above 42 ?(the temperature required for high temperature treatment)while maintaining healthy tissue at normal body temperature.Several useful methods have been proposed to direct microwave energy to cancerous tissue,including novel focusing methods and innovative microwave hardware designs.However,a number of challenges of limiting the use of microwave systems in clinical medicine still exist.It can be said that the most persistent engineering problem to overcome is to achieve locally focused microwave power in the complex medium environment of the breast.In order to understand the challenges of microwave hyperthermia,considerably large computational efforts are required to solve 3D Electromagnetic(EM)problems in a complex model of breast tissue.The success of using microwave hyperthermia to treat breast cancer largely depends on the accuracy of the excitation signal used for each antenna element.Several research papers have reported various approaches on this topic.Although recent progress has been made in the investigation of microwave hyperthermia,the studies were mainly reliant upon oversimplified Radio Frequency(RF)models which assume point source applicators,and human breast phantoms which are mostly 2D models lacking tissue thermal-electric properties.Therefore,the application of these systems in the clinic is not feasible.This thesis aims to address the limitations of these early studies by modeling and building 3D human breast models and 3D antenna arrays.This will need to be achieved by using the correct phase and amplitude of the optimized excitation signal.While a large proportion of tumors appear at superficial locations in the four quadrants of the breast.Based on this fact this thesis uses the high-frequency structure simulation software HFSS to design a breast cancer microwave hyperthermia conformal array antenna operating at 915MHz,which that allows microwave energy to be targeted to tumors located at different locations in the four quadrants of the breast by using a fixed antenna array.After calculating the specific absorption rate(SAR)in the breast using HFSS,the temperature field in the breast was solved by using the multiphysics simulation software COMSOL Multiphsics.In this study,microwave hyperthermia was performed in a real-world environment rather than an oversimplified scenario.In this method,microwave hyperthermia is performed in a 3D environment and takes into account the thermoelectric properties of the breast tissue.Simulation and experimental results show that by optimizing the phase of each array element of the array antenna,the microwave energy can indeed be offset within the breast to focus at different positions in the four quadrants of the breast.The main research contents of the thesis include:1.Overview of research status of breast cancer microwave hyperthermia at home and abroad:in particular,the thermal dose planning based on numerical simulation technology,the tumor hyperthermia method based on new materials,invasive and non-invasive microwave hyperthermia radiator are introduced in detail.The mechanism of microwave hyperthermia treatment of breast cancer tumors is briefly introduced.2.The numerical methods and calculation tools used in the design of the thermotherapy antenna are introduced:the calculation tools include:the electromagnetic simulation tool HFSS for estimating the breast absorption power,and the thermal simulation tool COMSOL Multiphysics for calculating the induction temperature generated by the microwave power.3.Designing a compact unit antenna and antenna array:in previous studies,the antenna was modeled as an ideal source.In order to improve system performance,the antenna must be compact to provide flexibility for forming complex 3D antenna arrays.The antenna array is designed such that electromagnetic energy can be focused at different locations in the superficial layers of the four quadrants within the breast phantom.4.Fabrication of the breast phantom and antenna:to make a realistic breast phantom,the phantom should have the size of the human breast and its physical characteristics.5.Microwave hyperthermia experiment:the performance of the proposed antenna was verified by experiments on a microwave hyperthermia system.