Year

2021

Degree Name

Doctor of Philosophy

Department

School of Physics

Abstract

Despite extensive research into improvements in brain cancer treatment, the cancer re- lated mortality since 1983 has remained nearly constant. Synchrotron-based radiotherapy microbeam radiation therapy (MRT) has emerged as a promising novel treatment aimed at improving tumour control while reducing normal tissue toxicities in brain cancer pa- tients. The complex features of the synchrotron source and microbeam (MB) array re- quires careful consideration in the quest towards the progression of MRT to clinical trials. The research presented in this PhD thesis aims contributes to the international field of re- search through advances in MRT quality assurance (QA) processes relating to treatment planning, dosimetry and treatment delivery verification. Specifically, this thesis evalu- ates an independent Geant4 Treatment Planning System (TPS) verification tool, a novel p-type epitaxial silicon strip detector, and finally the transmission characteristics of two silicon–based multi-strip detectors for transmission–based real-time beam monitoring in MRT.

One major outcome is the development and implementation of the first exclusive Geant4 Monte Carlo model of the Imaging and Medical Beamline (IMBL) at the Australian Syn- chrotron (AS). This model was successfully validated experimentally, with agreement between simulated and measured broadbeam (BB) and microbeam (MB) dose distribu- tions within 3% and 5% respectively for all investigated configurations and measure- ment depths. Through this development, the research identified a potential limitation in the G4SynchrotronRadiation process when modelling the synchrotron radiation pro- duction in variable magnetic fields. Correction factors are necessary to account for the synchrotron radiation production modelling limitations in key MRT beamline configura- tions. The novel p-type epitaxial silicon strip detector demonstrates desirable detector characteristics for implementation in high resolution MRT dosimetry. Notable improve- ments, over a previous generation device, include improvement in the energy dependence (relative to water) and spatial resolution. The improvements in detector design pioneer a method for developing accurate silicon-based dosimetry for application in routine MRT QA. Suitable implementation enables pre-clinical trials and future clinical trials. Further work investigates the impact of a novel back-etched silicon–based multi-strip beam mon- itor on the MRT beam quality and dose deposition characteristics. Evaluated by means of Monte Carlo simulation and experimental methods, recommendations are made for implementing and modelling silicon–based beam monitors within the context of a future TPS.

This thesis is unavailable until Wednesday, July 12, 2023

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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.