The Circuit System Design And Study On Temperature Measurement For Microwave Hyperthermia Apparatus

Hyperthermia treatment is a method for tumors by heating. In general, carcinoma cell is not all dead after radiotherapy and chemotherapy, such as three phases of mitotic cycle, low PH value and bad nutritional status hypoxic cell because of ishernia in the center of the tumors. They are the cause of cancer recurrence. It is effective to kill them by hyperthermia treatment. So good results would be obtained to combine hyperthermia treatment with radiotherapy or chemotherapy. That has been proved and obtained good results. Microwave, radiofrequency, ultrasonic are used in hyperthermia treatment. There are few problems of overheat by microwave heating technology. It can be applied to flat tumor, such as rectum cancer. In this paper, mechanism of hyperthermia treatment and microwave heating technology are interpreted in detail, and other heating technology is introduced.The key of microwave heat therapy is to heat tumor above the temperature for hyperthermia treatment. If the temperature is lower tumor cell maybe diffuse, and if the temperature is higher normal tissue maybe get Damage. So it is important to measure the temperature of tumor accurately. But the microwave interference affects the temperature measure in the process of hperthermia treatment. The temperature sensor made of metal material will produce induced current in microwave field, which will bring error. In this paper,the method that the sensor is shielded with metal layer,and temperature measuring circuit is designed.The experimentation proved that the method was effective .It is feasible in theory.Temperature measure in hyperthermia treatment is for controlling the temperature of the tumor, and the temperature of the tumor can be kept that for hyperthermia treatment. The user can control it by changing the output power of microwave and the time of hyperthermia treatment. The essence is to control the power supply. Microwave is produced by magnetron in the microwave hyperthermia apparatus. The user can control the power output of microwave. Magnetron don't produces microwave until the anode voltage increases enough,and a positive relationship exists between the power output of microwave and the anode current of magnetron. So the power supply must output enough voltage ,and the voltage can be changed. In this paper,the author selected magnetron for the household electric appliance as microwave generator. The working voltage decreases by improving the magnetron ,which improves the reliability and safety of the microwave hyperthermia apparatus and reduced design requirement of the power supply. This paper introduces the design of the switch power for magnetron.The author designed the main circuit of the power supply and auxiliary circuit. Flyback topological Structure is applied to the power supply. The user can change the duty ratio to controled the output current and voltage.The experimentation showed that the power supply output enough voltage and the magnetron can output different power of micrwave.In this paper,the author analysed the circuit by Pspice. So the time of designing circuit becomes shorter, the cost is reduced.