Optimizing microwave hyperthermia antenna systems

This thesis presents design and optimization of a microwave hyperthermia antenna system for treatment of head and neck cancer as well as brain cancer. Hyperthermia has shown the ability to enhance the performance of radiotherapy and chemotherapy in many clinical trials. The incidence of increased tissue toxicity as a result of high radiotherapy dose has made hyperthermia a safe complementing, treatment enhancing method to use in combination with radiotherapy. Although many clinical studies have shown the effectiveness of hyperthermia for treatment of the head-and-neck (H&N) cancer, the presence of large vessels, tissue transitions and critical tissues in the head and neck poses therapeutic challenges for treatment of advanced tumors in this region. Late side-effects of conventional therapies in treatment of brain tumors in children have been made hyperthermia an attractive method. However, heating tumors in the brain is even more challenging because of its high sensitivity, high thermal conductivity and high perfusion. In this thesis microwave hyperthermia applicators are presented for efficient heating of the H&N and brain tumors. For this purpose, an ultra-wideband antenna has been designed, built and evaluated to act as the radiating element of microwave hyperthermia applicators. The time reversal focusing technique is used to target electromagnetic energy into the tumor. To obtain more accurate treatment planning, the effect of frequency and virtual source positions, in the time-reversal method, are studied for different tumor sizes and tumor positions. The optimal detailed design of the applicator, such as the number of antennas and the antenna positions are also investigated. In the second part of the thesis, the focus is on the applicators for treatment of the brain tumors in children. Helmet applicators are presented and the effect of the number of antennas and the frequency are investigated on the performance of the applicators for heating large and deep-seated brain tumors. Finally, the optimum position of antennas in helmet applicators are found by performing optimization on simplified and realistic models of the child head.