Time-Multiplexed Beamforming for Noninvasive Microwave Hyperthermia Treatment

Abstract—A noninvasive microwave beamforming strategy is proposed for selective localized heating of biological tissue. The proposed technique is based on time multiplexing of multiple beam-formers. We investigate the effectiveness of the time-multiplexed beamforming in the context of brain hyperthermia treatment by using a high-fidelity numerical head phantom of an adult female from the Virtual Family (IT’IS Foundation) as our testbed. An op-erating frequency of 1 GHz is considered to balance the improved treatment resolution afforded by higher frequencies against the in-creased penetration through the brain afforded by lower frequen-cies. The exact head geometry and dielectric properties of biologi-cal tissues in the head are assumed to be available for the creation of patient-specific propagation models used in beamformer de-sign. Electromagnetic and thermal simulations based on the finite-difference time-domain method are used to evaluate the hyper-thermia performance of time-multiplexed beamforming and con-ventional beamforming strategies. The proposed time-multiplexing technique is shown to reduce the unintended heating of healthy tis-sue without affecting the treatment temperature or volume. The efficacy of the method is demonstrated for target locations in three different regions of the brain. This approach has the potential to improve microwave-induced localized heating for cancer treatment via hyperthermia or heat-activated chemotherapeutic drug release. Index Terms—Beamforming, biomedical applications of electro-magnetic (EM) radiation, brain cancer treatment, finite-difference time-domain (FDTD) methods, microwave hyperthermia. I