A mixed frequency approach to optimize locoregional RF hyperthermia

Locoregional hyperthermia is usually performed using phased-array systems, consisting of multiple RF antennas operating at a single frequency. This study investigated the use of a mixed frequency approach to improve the quality of heating. Simulations in a homogeneous phantom and in 5 patient anatomies were performed for systems consisting of rectangular waveguides operating at 70 and 140 MHz. Phantom results were very promising and showed a 20% lower superficial SAR deposition compared to the central target region for a 3-ring system with the central ring consisting of 140 MHz waveguides and the other two rings consisting of 70 MHz waveguides. In patient anatomies however, this benefit did not last, so further research is required to determine the optimal mixed frequency strategy for clinical use.