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

The variations of the specific absorption rate (SAR) and thermal distributi ons in the JSHO QA phantom were investigated by using the radiofrequency (R F) capacitive intracavitary hyperthermia (ICHT) applicator (AP-T01, Omron E lectric Co., Kyoto, Japan) and the opposite flat applicators of different s izes (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 bec ame weaker with the increase in size of the opposite flat applicator, and i t became stronger with the decrease of the distance between both applicator s. Heating near the flat applicator became weaker with the increase in size of the flat applicators, and it showed no apparent difference with the inc rease of the distance between both applicators. The normalized SAR values b etween AP-T01 and the opposite flat applicator became smaller and its slope became steeper with the increase in size of the opposite flat applicator a nd in the distance between both applicators. These results suggest that the variability of the specific absorption rate (SAR) and thermal distribution s of the region between both applicators may show the potentiality of usefu lness for heating the tumours of various sizes, shapes and location.