Comparison of a Capacitive and a Cavity Slot Radiative Applicator for Regional Hyperthermia

The performance of a capacitive and a radiative annular phased array applicator for regional hyperthermia is compared in a model study, for an agar-bone phantom and a structured patient anatomy with a prostate tumour. The capacitive applicator is a model of the Thermotron RF8 device, operating at 8 MHz. Its performance is improved by the use of very cold overlay boli with a suitable salinity. The radiative applicator is a three ring, cavity slot annular array applicator, operating at 150 MHz. The Specific Absorption Rate (SAR) distribution in the cavity slot applicator is optimized by phase-amplitude control. Comparison of both SAR and thermal distributions shows that the radiative applicator can generate good tumour heating in the pelvic region and avoid the overheating of superficial fat layers and muscle tissue seen in the capacitive applicator.