LET-Dependent Intertrack Yields in Proton Irradiation at Ultra-High Dose Rates Relevant for FLASH Therapy
- 2 October 2020
- journal article
- research article
- Published by Radiation Research Society in Radiation Research
- Vol. 194 (4), 351-362
- https://doi.org/10.1667/rade-20-00084.1
Abstract
FLASH radiotherapy delivers a high dose (≥10 Gy) at a high rate (≥40 Gy/s). In this way, particles are delivered in pulses as short as a few nanoseconds. At that rate, intertrack reactions between chemical species produced within the same pulse may affect the heterogeneous chemistry stage of water radiolysis. This stochastic process suits the capabilities of the Monte Carlo method, which can model intertrack effects to aid in radiobiology research, including the design and interpretation of experiments. In this work, the TOPAS-nBio Monte Carlo track-structure code was expanded to allow simulations of intertrack effects in the chemical stage of water radiolysis. Simulation of the behavior of radiolytic yields over a long period of time (up to 50 s) was verified by simulating radiolysis in a Fricke dosimeter irradiated by 60Co γ rays. In addition, LET-dependent G values of protons delivered in single squared pulses of widths, 1 ns, 1 µs and 10 µs, were obtained and compared to simulations using no intertrack considerations. The Fricke simulation for the calculated G value of Fe3+ ion at 50 s was within 0.4% of the accepted value from ICRU Report 34. For LET-dependent G values at the end of the chemical stage, intertrack effects were significant at LET values below 2 keV/µm. Above 2 keV/µm the reaction kinetics remained limited locally within each track and thus, effects of intertrack reactions remained low. Therefore, when track structure simulations are used to investigate the biological damage of FLASH irradiation, these intertrack reactions should be considered. The TOPAS-nBio framework with the expansion to intertrack chemistry simulation provides a useful tool to assist in this task.Keywords
This publication has 62 references indexed in Scilit:
- On the spur lifetime and its temperature dependence in the low linear energy transfer radiolysis of waterPhysical Chemistry Chemical Physics, 2012
- TOPAS: An innovative proton Monte Carlo platform for research and clinical applicationsMedical Physics, 2012
- Comparison of GEANT4 very low energy cross section models with experimental data in waterMedical Physics, 2010
- Monte Carlo simulation study of the effects of acidity and LET on the primary free-radical and molecular yields of water radiolysis — Application to the Fricke dosimeterCanadian Journal of Chemistry, 2007
- Effect of Multiple Ionization on the Yield of H2O2Produced in the Radiolysis of Aqueous 0.4MH2SO4Solutions by High-LET12C6+and20Ne9+IonsRadiation Research, 2005
- Hydrated Electron Yields in the Heavy Ion Radiolysis of WaterThe Journal of Physical Chemistry A, 2005
- Stochastic modeling of fast kinetics in a radiation trackThe Journal of Physical Chemistry, 1990
- Unexpected Dose-rate Effect in the Killing of Mice by RadiationNature, 1966
- Hugo Fricke and the Development of Radiation Chemistry: A Perspective ViewRadiation Research, 1962