Modelling Low LET Flash Radiotherapy Pulse Trains

  • Robert Ross

Student thesis: Unknown

Abstract

This thesis investigates the use of Linear Quadratic (LQ) modelling of in vitro Flash cell survival to predict differences in cell survival caused by different radiation pulse train parameters. Currently, pulse train parameters are not considered when modelling cell survival. Oxygen depletion is hypothesised to be a key component of the Flash effect. Established literature shows oxygen is a powerful radiosensitiser which depletes with each pulse and significant reoxygenation can occur on timescales of the order used between Flash pulses. Older literature implying increased cell survival due to oxygen depletion tended to use single pulses of radiation, with no possibility of reoxygenation, yet are frequently cited as evidence of the Flash effect. These often predate the Linear Quadratic (LQ) modelling of cell survival, and sometimes show a discrete change in cell survival (the ‘breakpoint dose’) ascribed to oxygen depletion. I ask if LQ modelling can demonstrate a pulse train effect and what is the magnitude of the effect. Using historical and modern data from my non-systematic literature survey, I test LQ against Flash-style cell survival data and establish cellular oxygen values immediately prior to each radiation pulse, based on established theories of oxygen depletion and reoxygenation. Using a recent method of relating oxygen value to LQ parameter β, I derive cell survival values based on different pulse train parameters and compare them to a published survival curve for one pulse train. I show that the results are systematically different, but may be masked by experiment uncertainty. The significance of this study is to establish if choice of pulse parameters can influence the outcomes of experiment or clinical use, to ensure optimal Flash effect is being utilised.
Date of Award1 Aug 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorMike Merchant (Supervisor)

Keywords

  • Flash
  • Radiotherapy
  • Pulse Trains
  • Low LET

Cite this

'