The Development Of 915MHz Microwave Therapy Apparatus And The Research Of Its Application In Microwave Phantom

Objective: With the advancement of microwave technology,microwave hyperthermia has been used for the treatment of many diseases,such as rehabilitation physiotherapy,microwave ablation,microwave coagulation therapy,and so on.The core technology of the microwave therapy instrument is to design a radiant antenna with high heating efficiency and safety.The currently used extracorporeal thermotherapy instrument uses a single antenna or an array antenna system without automatic adjustment of the heating part.Manual adjustment will increase the difficulty of treatment.Traditional microwave therapytherapy apparatus have a larger volume and do not have the function of heating large-area lesions.This project aims to design a new type of microwave therapy apparatus mainly for the treatment of soft tissue diseases.This paper build the microwave hyperthermia phantom and investigate the warming effect of the apparatus on the microwave phantom.The result will providing a basis for subsequent experiments.Methods:1.This paper used 915 MHz microwave signal as signal source and selected the substrate,determined size and feeding method.A 4X4 16-element microstrip antenna was designed.This paper Designed MCU,phase shifter and power divider according to system requirements,and simulated the near field electromagnetic distribution,focal length,focus intensity,etc.in the HFSS electromagnetic simulation software.2.Sodium carboxymethyl cellulose,PVC powder,deionized water and sodium chloride were used to prepare the muscle microwave phantom.This phantom has Dielectric properties consistent with human muscle tissue.3.The configured phantom was placed in a 100 ml beaker.After the phantom was still formed,it was preheated to 37? in a thermostatic water bath container.The specific practices are as follows:First,The phantom was placed 20 cm below the microwave therapy device.The microwave therapy apparatus was turned on after the temperature of the phantom was measured.Second,The microwave phantom temperatures of 0 cm,2 cm,4 cm,and 6 cm from the surface of the microwave phantom were measured every 3minutes by using a TM902 C thermometer.The heating time was 15 minutes in total.Third,The above steps were repeated three times.4.First,the phantom was placed in a 15cm*15cm plastic mold,which can be divided into 9 square areas of 5*5cm,5 of which correspond to the beam focus point after the phase shifter changed.In the same way,The phantom was preheated to 37?,and then placeed at 20 cm under the microwave therapy apparatus.After 15 minutes,The temperature of the five adjustable regions was measured,The above steps were repeated three times.Second,The focus area of the antenna was changed on the computer and the above temperature measurements steps were repeated three times.Finally,the focus area of the antenna was changed once again on the computer and the temperature measurements steps were repeated three times.All the temperature data was collected and analyzed to get the temperature rising rule of of the microwave thermal field in the phantom.Results:1.An active phased array antenna microwave therapeutic instrument based on a microstrip antenna structure was designed in this study.It is composed of 16 microstrip antennas with a size about 238mm*246mm.Electromagnetic distribution,focal length,focusing intensity and other electromagnetic characteristics are simulated in the HFSS.The antenna has good focusing performance and the focal length of the antenna is 200 mm away from the antenna,and the focal diameter is about 40 mm.The phase shifter can adjust the five focusing areas on the plane 200 mm away from the antenna.2.The phantom configured by Sodium carboxymethyl cellulose,polyvinyl chloride powder,deionized water,sodium chloride has the same dielectric properties as human tissue.3.The microwave therapy apparatus has a certain temperature distribution and heating characteristics when heating the phantom.Within the focus range,the tendency of the phantom to warm up is that the maximum temperature increases first and then decreases with the increase of depth,and the temperature rises fastest at 0cm,2cm.The temperature tends to be stable when heated for 12 minutes.During the entire heating process,the temperature of the phantom at a depth of 0cm to 4cm is within the treatment range,and the temperature at 6cm from the surface of the phantom is not within the treatment range and tends to decrease.4.In the measurement experiment of the electronically controlled adjustment of the microwave beam,the phase shifter's control of the microwave signal focus area is consistent with the highest temperature area actually measured,which can realize the mobile position of the treatment.Conclusion:1.The manufactured microwave phantom has good muscle electromagnetic simulation,and is simple to configure and easy to save.It can be used for microwave electromagnetic research and provide a basis for animal and clinical experiments.2.The 915 MHz microwave therapy apparatus is simple and easy to operate.The maximum heating temperature shall not exceed the tissue safety temperature of 45?.It is mainly suitable for the treatment of superficial soft tissue diseases at a distance of 20 cm from the lesion and providing reference for the subsequent animal and clinical experiments.