The size and distance of the opposite flat applicator change the SAR and thermal distributions of RF capacitive intracavitary hyperthermia

Abstract

The variations of the specific absorption rate (SAR) and thermal distributions in the JSHO QA phantom were investigated by using the radiofrequency (RF) capacitive intracavitary hyperthermia (ICHT) applicator (AP-T01, Omron Electric Co., Kyoto, Japan) and the opposite flat applicators of different sizes (AP-75E: 7.5 cm in diameter, AP-100E: 10 cm in diameter, and AP-150E: 15 cm in diameter). The influences of the distance between both applicators were also investigated. Heating of the region between both applicators became weaker with the increase in size of the opposite flat applicator, and it became stronger with the decrease of the distance between both applicators. Heating near the flat applicator became weaker with the increase in size of the flat applicators, and it showed no apparent difference with the increase of the distance between both applicators. The normalized SAR values between AP-T01 and the opposite flat applicator became smaller and its slope became steeper with the increase in size of the opposite flat applicator and in the distance between both applicators. These results suggest that the variability of the specific absorption rate (SAR) and thermal distributions of the region between both applicators may show the potentiality of usefulness for heating the tumours of various sizes, shapes and location.