DEVELOPMENT OF RE-ENTRANT TYPE RESONANT CAVITY APPLICATOR FOR DEEP TUMOR HYPERTHERMIA

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In this research project, a new heating system using a re-entrant resonant type cavity applicator for deep-seated tumor hyperthermia treatment is proposed. The developed heating system consists of a re-entrant type resonant cavity made of an aluminum alloy, an RF (radio frequency) amplifier, a power supply unit, a matching unit, and a microcomputer. To verify the possibility of this heating system for deep-seated tumor, the following three experiments using cylindrical phantoms and dogs were perfomed :(1) The agar phantom used in this experiment was 27.0cm in diameter and 25.0cm high. Heating pattems were observed with a thermographic camera. The thermal image of the vertical sectional slice of the agar phantom clearly showed that the center region of the phantom was heated concentrically, as expected.(2) The three layred lard agar phantom was used in the experiment. The agar phantom, wich 20.0cm in thickness, was sandwiched between the two lard-disk layrs, which were 2.0cm and 1.5cm in thickness respectively. Although small hot spots, due to the edge effect, appeared in the lard layrs, maximum temperature still appeared at the center region of the phantom.(3) The final experiment was to heat the liver and brain of a beagle dog. Fiber optic temperature sensors were placed at four points in the dog's tissue. Against much blood perfusion in these tissues, the measured temperatures at the deepest region was 0.5-0.7ﾟC higher than the other regions of the tissue.From these experimental heating results, it is confirmed that the system can be applicable to both local and deep tumor hypethermia.