The modelling of biological systems in three dimensions using the time domain finite-difference method: II. The application and experimental evaluation of the method in hyperthermia applicator design.

The three-dimensional time domain finite-difference (TDFD) method was used to design a 433 MHz circular waveguide applicator for electromagnetic hyperthermia. This applicator has a water-filled lens at one end, providing surface cooling as well as some shaping of the emergent electromagnetic field. An experimental system for scanning the EM field in three dimensions is described. The experimental data were compared with those calculated from the TDFD program and good agreement was found. A realistic three-dimensional model based on an ultrasound scan of a surface tumour was built. Both the EM field and the specific absorption rate (SAR) within the model when irradiated by the applicator were calculated.