| At present,breast cancer has replaced lung cancer and become the world’s largest cancer.Traditional treatment methods for breast cancer(radiotherapy,chemotherapy,hormone therapy,etc.)all have serious side effects.Microwave hyperthermia has many advantages such as wide applicability,side effects and low damage to healthy tissues compared with other therapies.It is known as the "green therapy" for cancer therapy.In this method,the fixed frequency electromagnetic wave is quantitatively transmitted to the tumor site through the focusing of multiple radiators,the electromagnetic energy is converted into heat and deposited at the tumor site,so that the temperature of the tumor site is increased to 41.5 ℃,and the temperature of healthy tissue is maintained in the normal range.However,the target location of tumor is often not fixed.How to use a radiator to treat multiple tumors by changing the feeding mode has become a new challenge.Under this research background,this thesis studies the scheme of near-field array antenna focusing in the treatment of tumors in different parts of the breast with the help of numerical simulation and image processing.The main research contents include the following three aspects:Above all,a 17 element array antenna working at 915 MHz is designed.The breast model,external environment and antenna element are modeled.The parameter design and array arrangement of antenna element are simulated and optimized by using HFSS simulated electromagnetic field.By adding deionized water to reduce the antenna size,the distance between antenna and skin,the length of Teflon sheath and other parameters are optimized,The return loss of each antenna element is optimized below-10 d B.The return loss of each antenna element is measured under the experimental conditions.The experimental results show that the return loss of each antenna element at 915 MHz is less than-10 d B,which can meet the application requirements.Furthermore,The feed phase and power of the 17-array array antenna are optimized,and the SAR field and temperature field of the array antenna are focused on different parts of the breast by changing the feeding method of different array elements,and 33 feed schemes with the electromagnetic field center focused on different positions of the breast pitch angle and azimuth angle are obtained,and the temperature field distribution of the feed scheme is simulated and verified by COMSOL software.The simulation results show that by controlling the feed phase of different arrays,the goal of forming a temperature field above 41.5°C in multiple places inside the breast is achieved.In addition,we designed an image matching software for 17 element array antenna to treat breast cancer.Through filtering and two value processing of simulated tumor images and simulated images at different parts of the temperature field,the location,size and shape of the tumor were matched with the location and size information of the treatment area.The feeding scheme of 17 element array antenna for tumors with different sizes and depths at different positions is provided.Finally,in order to verify the heating effect of 17 element array antenna,the experiment of body film hyperthermia was carried out on the array antenna.In the experiment,a 9-channel microwave source was used to control the phase and power of the output signal of the microwave source through the host computer to feed each array element of the array antenna.The body membrane was used to simulate the breast tissue,and thermochromic materials were added to see the treatment effect.In the whole process of the experiment,a peristaltic pump was used to cool the deionized water.The experimental results show that under different feeding schemes,the actual heating area is consistent with the temperature field obtained by numerical simulation. |
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