6–10 Jul 2026
University of the Western Cape
Africa/Johannesburg timezone
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A Geant4 Study of FLASH Proton Therapy Mechanisms

8 Jul 2026, 09:50
20m
Lecture Hall DL3 (University of the Western Cape)

Lecture Hall DL3

University of the Western Cape

Oral Presentation Track F - Applied Physics Applied Physics

Speaker

Marry Thekhwe (University of Cape Town)

Description

Ultra-high dose rate (UHDR), mostly referred to as FLASH radiotherapy, has emerged as a promising treatment modality capable of reducing normal tissue toxicity in a cancerous tumour. However, the underlying physical and radiochemical mechanisms of this FLASH radiotherapy remain incompletely understood. In this study, high-dose-rate proton irradiation was investigated using Monte Carlo simulations within the Geant4 framework to examine energy deposition in liquid water to understand the physical and radiochemical mechanisms of FLASH proton radiotherapy. At the macroscopic level, depth dose distributions, Bragg peak characteristics, and linear energy transfer (LET) variations are quantified for clinically relevant proton energies. At the microscopic level, track-structure simulations were used to model particle interactions at nanometric scales, which allowed for the analysis of ionisation clustering and radial dose distributions in both the entrance region and near the Bragg peak. By comparing these regions, the evolution of the proton track structure relative to depth was characterised. The relationship between macroscopic dose metrics and microscopic energy deposition was then examined to assess implications for early-stage radiochemical processes, including water radiolysis. Particular attention was given to conditions relevant to FLASH irradiation, where high instantaneous dose rates may influence energy deposition and subsequent chemical interactions. This work provides a simulation-based framework linking physical dose deposition to underlying microscopic processes.

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Author

Marry Thekhwe (University of Cape Town)

Co-authors

Dr Batmunkh Munkhbaatar (Joint Institute for Nuclear Research) Dr Daphney Bucher (University of Cape Town) Dr Mpfareleni Rejoyce Gavhi-Molefe (African Institute for Mathematical Sciences) Prof. Steve Peterson (University of Cape Town)

Presentation materials