Year

2020

Degree Name

Doctor of Philosophy

Department

School of Physics

Abstract

Despite constant advancements in the treatment of cancer using chemotherapy, radiotherapy, and surgical intervention, the rate of survival for patients with head-and-neck cancers has remained steady at 30% for almost 30 years in Australia. Microbeam Radiation Therapy (MRT) is a preclinical radiotherapy modality that shows promise in improving positive treatment outcome rates for such patients.

MRT takes advantage of the specialised properties of synchrotron radiation generated from an insertion device, namely the high intensity and small divergence of the resulting photon beam. This allows the incident photon beam (a.k.a the broadbeam) to be collimated to produce an array of micrometre-width, spatially fractionated, high dose rate microbeams. The resulting shape of the lateral dose profile is that of high dose rate ‘peaks’ separated by low dose rate ‘valleys’. Typical widths and pitch of the microbeams are 25–50 µm and 200–400 µm, respectively.

By taking advantage of the Dose-Volume Effect, where the tolerance of normal tissue to radiation damage increases dramatically as the radiation field size decreases, much higher treatment doses may be delivered than possible with conventional radiotherapy techniques. The low divergence of synchrotron radiation allows the microbeam array to maintain its structure even at depth in a patient, which leads to greater preferential damage to tumours and less normal tissue damage, thus leading to better positive treatment outcomes. Combined with the small field sizes of MRT compared to conventional radiotherapy techniques, MRT is well suited to treatment of small, radioresistant cancers that are in close proximity to sensitive normal tissue, such as brain gliomas. However, the small field sizes and high dose rates (hundreds to thousands of Gy/s) pose a challenge for dosimetry and treatment due to the increased risks and severity of consequence of errors in dose delivery. In order to progress to clinical trials in humans, rigorous quality assurance (QA) is necessary, both in the field of experimental dosimetry and in simulations for treatment planning.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.