Antenna Design, Radiobiological Modelling, and Non-invasive Monitoring for Microwave Hyperthermia

Licentiate thesis, 2022

The death toll of cancers is on the rise worldwide and surviving patients suffer significant side effects from conventional therapies. To reduce the level of toxicity in patients treated with the conventional treatment modalities, hyperthermia (HT) has been investigated as an adjuvant modality and shown to be a potent tumor cell sensitizer for radio- and chemotherapy. During the past couple of decades, several clinical radiofrequency HT systems, aka applicators, have been developed to heat tumors. Systems based on radiative applicators are the most widely used within the hyperthermic community. They consist of a conformal antenna array and need a beamforming method in order to focus EM energy on the tumor through constructive interference while sparing the healthy tissue from excessive heating. Therefore, a hyperthermia treatment planning (HTP) stage is required before each patient's first treatment session to optimize and control the EM power deposition as well as the resultant temperature distribution.

Despite the vast amount of effort invested in HTP and the progress made in this regard during recent years, the clinical exploitation of HT is still hampered by technical limitations and patients can still experience discomfort during clinical trials. This, therefore, calls for a more efficient hardware design, better control of EM power deposition to minimize unwanted hotspots, and more accurate quantification and monitoring of the treatment outcome. Given these demands, the present report tries to address some of the above-mentioned challenges by proposing
- A new antenna model customized for HT applications that surpasses previously proposed models from several points of view.
- A hybrid beamforming method for faster convergence and a versatile, robust thermal solver for handling sophisticated scenarios.
- A radiobiological model to quantify the outcome of a combined treatment modality of the Gamma Knife radiosurgery and HT.
- A differential image reconstruction method to assess the feasibility of using the same system for both heating and microwave thermometry.