Regional hyperthermia applicator design using FDTD modelling

Recently published results confirm the positive effect of regional hyperthe rmia combined with external radiotherapy on pelvic tumours. Several studies have been published on the improvement of RF annular array applicator syst ems with dipoles and a closed water bolus. This study investigates the perf ormance of a next-generation applicator system for regional hyperthermia wi th a multi-ring annular array of antennas and an open water bolus. A cavity slot antenna is introduced to enhance the directivity and reduce mutual co upling between the antennas. Several design parameters, i.e. dimensions, nu mber of antennas and operating frequency, have been evaluated using several patient models. Performance indices have been defined to evaluate the effe ct of parameter variation on the specific absorption rate (SAR) distributio n. The performance of the new applicator type is compared with the Coaxial TEM. Operating frequency appears to be the main parameter with a positive i nfluence on the performance. A SAR increase in tumour of 1.7 relative to th e Coaxial TEM system can be obtained with a three-ring, six-antenna per rin g cavity slot applicator operating at 150 MHz.