Ultra wideband microwave hyperthermia for brain cancer treatment
Doctoral thesis, 2022

Despite numerous clinical trials demonstrating that microwave hyperthermia is a powerful adjuvant modality in the treatment of cancers, there have been few instances where this method has been applied to brain tumors. The reason is a combination of anatomical and physiological factors in this site that require an extra degree of accuracy and precision in the thermal dose delivery. Current clinical applicators are not able to provide such control, partly because they are designed to operate at a single fixed frequency. In terms of treatment planning, the use of a single frequency is limiting as the size of the focal spot cannot be modified to accommodate the specific tumor volume and location. The introduction of ultra wide-band (UWB) systems opens up an opportunity to overcome these limitations, as they convey the possibility of adapting the focal spot and obtaining different power deposition patterns to reduce the heating of healthy tissues.

In this thesis, we explore whether the current SAR-based treatment planning methods can be meaningfully translated to the UWB setting and propose new solutions for deep UWB microwave hyperthermia. We analyze the most commonly used cost functions for treatment planning optimization and discuss their suitability for use with UWB systems. Then, we propose a novel SAR-based cost function (HCQ) for UWB optimization that exhibits a high correlation with the resulting tumor temperature. To solve for the HCQ, we describe a novel, time-reversal-based, iterative scheme for a rapid and efficient optimization of UWB treatment plans. Next, we investigate the design possibilities of UWB brain applicators and introduce a fast E-field approximation scheme to quickly explore a large number of array configurations. The method determines the best antenna arrangement around the head with respect to the multiple objectives and requirements of clinical hyperthermia. Together, the proposed solutions manage to achieve the level of tumor coverage and hot-spot suppression that is necessary for a successful treatment. Finally, we investigate the benefit of integrating hyperthermia delivered by an optimized UWB applicator into the radiation therapy plan for a pediatric medulloblastoma patient. The results suggest that UWB microwave hyperthermia for brain cancer treatment is feasible and motivate efforts for further development of UWB applicators and systems.

ultra wideband

treatment planning

brain cancer

applicator design

time reversal

microwave hyperthermia

HC4, Hörsalsvägen 14
Opponent: Dr. Petra H. Kok, Amsterdam UMC, The Netherlands


Massimiliano Zanoli

Chalmers, Electrical Engineering, Signal Processing and Biomedical Engineering

Massimiliano Zanoli, Erika Ek, Hana Dobsicek Trefna, Antenna arrangement in UWB helmet brain applicators for deep microwave hyperthermia

Imagine being able to cause an inflammation-like state in a tumor, by raising its temperature just a few degrees centigrade above the baseline for a prolonged time. Even by this tiny amount, a cascade of biological responses is triggered in the body: blood rushes to the affected area, in an effort to counteract the extra heat; capillaries dilate to increase the exchange of oxygen and metabolites with the local tissues; the immune system, normally unaware of the threat posed by the altered cancer material, becomes more alert, and the white cells begin seeking for anomalies; the tumor enters a state of frenetic activity to restore its balance.

But we have prepared two deadly traps: the blood stream carries a poison with it, chemical agents with the ability to tamper with and kill the cancer cells. From the outside, incoming high energy gamma rays bomb the tumor's DNA causing breaks in the nucleotide chain. The tumor struggles to stem the damage, its internal repair mechanisms being inhibited by the exerted rise in temperature. Eventually, the fight reaches a tipping point and the tumor retreats.

This epic tale is regularly played out in patients afflicted by tumors in the pelvis, in the abdomen, in the breast, in the neck, and in the extremities, with remarkable results. The boost in survival rates speaks clearly: hyperthermia works. But a whole group of people has been left out by this advancement, namely brain cancer patients. The main reason behind this is the difficulty in implementing a controlled heat delivery inside the head with high enough accuracy for the treatment to be safe and effective.

In the present work, we devise new techniques for the non-invasive thermal treatment of tumors in the brain. We devote particular attention to young patients, where the incidence of such diseases is the highest, and where the long-lasting side effects of traditional therapies severely degrade the quality of life of survivors. Thanks to improvements in the control of the thermal dose delivery by means of innovative system designs and sophisticated steering tools, we show that it is possible to achieve therapeutic temperatures even in the nastiest of tumors. The wish is for microwave hyperthermia to become a regular modality in brain cancer treatment, and finally exploit the benefits of this technique in younger sufferers.

Focused Microwave Intracranial Heating: towards mitigation of late side effects of childhood brain cancer treatment

Swedish Research Council (VR) (2021-04935), 2022-01-01 -- 2025-12-31.

Subject Categories

Medical Equipment Engineering

Signal Processing

Areas of Advance

Health Engineering



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5235



HC4, Hörsalsvägen 14


Opponent: Dr. Petra H. Kok, Amsterdam UMC, The Netherlands

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