STUDY ON SEMICYLINDRICAL MICROSTRIP APPLICATOR FOR MICROWAVE HYPERTHERMIA

A semicylindrical microstrip applicator system is proposed and designe d, both for microwave heating and for noninvasive temperature estimati on, in application to hyperthermia treatment. The experimental results showed that the system functions both as a heating device and as a me ans of noninvasive temperature estimation. Therefore, electrical switc hing of these two functions makes the system realize both heating and temperature estimation. These functions reduce the pain of hyperthermi a therapy for patients. The system is constructed of a water-loaded cy lindrical applicator. Thus, the whole system can be made compact compa red to conventional applicators. This improvement allows for various m erits, such as realizing a surface cooling effect and decreased leakag e of electromagnetic (EM) waves. When the applicator is set as an arra y arrangement, the system can be used as a microwave heating device. T he penetration depth can be varied by adjusting phases of the EM wave radiated from each applicator. The experimental results at 430 MHz sho wed that semicylindrical microstrip applicators can be expected to be valid for tumor heating at depths within 55 mm. Moreover, by measuring transmission power between the two applicators, the system can be use d to estimate temperature inside the medium. The transmission power wh ich was measured in the frequency domain was converted in the time dom ain. By such a method, temperature distribution was calculated by solv ing simple simultaneous primary equations. The results of the temperat ure estimation show that the number of estimated temperature segments which have an error within 0.5-degrees-C is 28 out of 36. The system c an be easily used as a temperature measuring applicator as well as a h eating applicator.