Simulation and measurement of particle therapy beams with a silicon-based detection system

Abstract

In 2022, the World Health Organisation estimated that cancer is responsible for 9.7 million deaths worldwide per year [1]. Advances in recent years have continued to improve the understanding and treatment of cancer, making more cancers treatable and increasing treatment efficacy and survival rates [2]. Among current modalities, radiotherapy continues to plays a key role alongside chemotherapy and surgery where it is used to apply high doses of radiation to cancerous cells to kill or shrink tumours [3]. Particle therapy, particularly proton and carbon ion therapy, has gained increasing clinical adoption in recent decades, due to its superior dose conformity and the Bragg peak, which allow precise dose delivery to tumours while minimising irradiation of surrounding healthy tissue [4]. However, these advantages require precise dose delivery and accurate range verification to ensure that patients receive the correct dose at the correct location while protecting surrounding healthy tissues as much as possible. This work concentrates on the development of a water phantom tracking system using silicon pixel detectors for beam monitoring and range verification in particle therapy. Monte Carlo simulations have been used to predict the response of the tracking system, investigate the contributions of the dose deposition of primary and secondary radiation fields, and to calculate dose-depth profiles for both proton and carbon ion beams. These studies allowed a detailed characterisation of the Bragg peak at different energies and offered insights into the energy contributions and detector response under different conditions. Complementary simulations were performed using Allpix2 to understand the charge deposition and charge sharing effect of the HVTrack pixel detector. Experimental measurements with FE-I4b and Timepix3 pixel detectors integrated into the water phantom, were conducted using clinical proton beams at the Rutherford Cancer Centres, UK. Measurements of beam profiles and Bragg peaks were compared to simulation results, demonstrating a reasonable agreement and confirming the silicon pixel detectors’ capability for range verification and beam monitoring. The findings of this thesis contribute to the ongoing development of detection systems for quality assurance in particle therapy. The combination of Monte Carlo simulation tools and experimental measurements creates a robust framework to improve beam monitoring accuracy and enhance the clinical translation of silicon pixel detector technologies in radio- therapy.