SIMULATION STUDIES PROMOTE TECHNOLOGICAL-DEVELOPMENT OF RADIOFREQUENCY PHASED-ARRAY HYPERTHERMIA

A treatment planning program package for radiofrequency hyperthermia h as been developed. It consists of software modules for processing thre e-dimensional computerized tomography (CT) data sets, manual segmentat ion, generation of tetrahedral grids, numerical calculation and optimi sation of three-dimensional E field distributions using a volume surfa ce integral equation algorithm as well as temperature distributions us ing an adaptive multilevel finite-elements code, and graphical tools f or simultaneous representation of CT data and simulation results. Heat treatments are limited by hot spots in healthy tissues caused by E fi eld maxima at electrical interfaces (bone/muscle). In order to reduce or avoid hot spots suitable objective functions are derived from power deposition patterns and temperature distributions, and are utilised t o optimise antenna parameters (phases, amplitudes). The simulation and optimisation tools have been applied to estimate the improvements tha t could be reached by upgrades of the clinically used SIGMA-60 applica tor (consisting of a single ring of four antenna pairs). The investiga ted upgrades are increased number of antennas and channels (triple-rin g of 3 x 8 antennas and variation of antenna inclination. Significant improvement of index temperatures (1-2 degrees C) is achieved by upgra ding the single ring to a triple ring with free phase selection for ev ery antenna or antenna pair. Antenna amplitudes and inclinations prove d as less important parameters.