The Control Method Study And Software Design Of Alternated Cooling And Heating Treatment

The thermo-physical treatments had been used separately in tumor therapy for a long time. Nevertheless, during the past 30 years, several study had get the conclusion that the alternated cooling and heating was remarkably effective to destroy the tumor tissue than cryosurgery or hyperthermia alone. In addition, other great benefit can be found using this method: (1) the probe with high temperature can suppress the bleeding of the wound caused by penetration of cryosurgery; (2) the alternated cooling and heating will induce anti-tumor immune response which can prevent cancer transfer and recurrence.Our Lab has designed a new cryosurgery-hyperthermia treatment system using liquid nitrogen for cooling and Radio-frequency for heating. According the requirements, cryosurgery and hyperthermia can be operated separately or together. The diameter of the cryo-heat probe of the system is 2.5mm only, which could be decreased in the future. However, the control of the system is difficult due to the integration of cryosurgery and hyperthermia. What's more, with litter effective theory to consult, the system control method is imperfect and can't meet the requirement of clinical application. So the cryosurgery-hyperthermia treatment system can't serve the people who need it until a safe and reliable algorithm is designed.In this study, a fuzzy logic controller and a fuzzy logic PID controller are designed based on the thermal treatment system for cryosurgery and hyperthermia treatment separately. For tumor tissue between 10mm and 30mm, the edge temperature of the tumor can reach the desire value in 3 minutes, and the steady-state error is limited to 2℃in cryosurgery treatment and 1℃in hyperthermia treatment. So the quick response and accuracy control of temperature are achieved. At the same time, the gas-liquid nitrogen is use to keep the probe cool, which can improve the stability of hyperthermia treatment and extend the cure area. Finally, results of ex-vivo pig liver experiments and in-vivo experiments of rabbit and mouse demonstrate that this system could provide a good control for the desired treatment procedure via the proposed control method.