A simulation-based study on water radiolysis species for 1H+, 4He2+, and 12C6+ ion beams with multiple ionization using Geant4-DNA

Baba, Kentaro; Kusumoto, Tetsuya; Okada, S.; Ishikawa, Masayori

doi:10.1063/5.0054665

Cited by 5 publications

(5 citation statements)

References 41 publications

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“…Additionally, discrepancies between simulated yields of H 2 O 2 and experimental yields have been attributed to the fact that multiple ionizations of the same water molecule have no process in Geant4‐DNA. It was found that at high LET there was a reduction in the yield of H 2 O 2 due to these multiple ionizations 72 . The available H 2 O 2 is also implicated in the Fenton reaction, given by

\smash{${\mathrm{H}}_{2}{\mathrm{O}}_{2}+{\mathrm{Fe}}^{2+}\to {}^{\cdot}\mathrm{OH}+{\mathrm{OH}}^{-}+{\mathrm{Fe}}^{3+}$}

which, at the time the simulations were ran, could not be included due to the lack of appropriate chemical species, as well as time scale limitations in TOPAS‐nBio.…”

Section: Discussionmentioning

confidence: 99%

“…It was found that at high LET there was a reduction in the yield of H 2 O 2 due to these multiple ionizations. 72 The available H 2 O 2 is also implicated in the Fenton reaction, given by H 2 O 2 + Fe 2+ → ⋅ OH + OH − + Fe 3+ which, at the time the simulations were ran, could not be included due to the lack of appropriate chemical species, as well as time scale limitations in TOPAS-nBio. It's importance lies not only in the modification of the yield of H 2 O 2 , but also in the fact that the potential high levels of H 2 O 2 in the MB peaks may catalyze this reaction, thereby producing cytotoxic ⋅ OH.…”

Section: Discussionmentioning

confidence: 99%

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Monte Carlo study of the free radical yields in minibeam radiation therapy

Masilela

Prezado

2023

Medical Physics

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BackgroundMinibeam radiation therapy (MBRT) is a novel technique which has been shown to widen the therapeutic window through significant normal tissue sparing. Despite the heterogeneous dose distributions, tumor control is still ensured. Nevertheless the exact radiobiological mechanisms responsible for MBRT efficacy are not fully understood.PurposeReactive oxygen species (ROS) resulting from water radiolysis were investigated given their implications not only on targeted DNA damage, but also for their role in the immune response and non‐targeted cell signalling effects: two potential drivers of MBRT efficacy.MethodsMonte Carlo simulations were performed using TOPAS‐nBio to carry out the irradiation of a water phantom with beams of protons (pMBRT), photons (xMBRT), 4He ions (HeMBRT), and 12C ions (CMBRT). Primary yields at the end of the chemical stage were calculated in spheres of 20 μm diameter, located in the peaks and valleys at various depths up to the Bragg peak. The chemical stage was limited to 1 ns to approximate biological scavenging, and the yield of · OH, H2O2, and was recorded.ResultsBeyond 10 mm, there were no substantial differences in the primary yields between peaks and valleys of the pMBRT and HeMBRT modalities. For xMBRT, there was a lower primary yield of the radical species · OH and at all depths in the valleys compared to the peaks, and a higher primary yield of H2O2. Compared to the peaks, the valleys of the CMBRT modality were subject to a higher · OH and yield, and lower H2O2 yield. This difference between peaks and valleys became more severe in depth. Near the Bragg peak, the increase in the primary yield of the valleys over the peaks was 6% and 4% for · OH and respectively, while there was a decrease in the yield of H2O2 by 16%. Given the similar ROS primary yields in the peaks and valleys of pMBRT and HeMBRT, the level of indirect DNA damage is expected to be directly proportional to the peak to valley dose ratio (PVDR). The difference in the primary yields implicates a lower level of indirect DNA damage in the valleys compared to the peaks than what would be suggested by the PVDR for xMBRT, and a higher level for CMBRT.ConclusionsThese results highlight the notion that depending on the particle chosen, one can expect different levels of ROS in the peaks and valley that goes beyond what would be expected by the macroscopic PVDR. The combination of MBRT with heavier ions is shown to be particularly interesting as the primary yield in the valleys progressively diverges from the level observed in the peaks as the LET increases. While differences in the reported · OH yields of this work implicated the indirect DNA damage, H2O2 yields particularly implicate non‐targeted cell signalling effects, and therefore this work provides a point of reference for future simulations in which the distribution of this species at more biologically relevant timescales could be investigated.

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\smash{${\mathrm{H}}_{2}{\mathrm{O}}_{2}+{\mathrm{Fe}}^{2+}\to {}^{\cdot}\mathrm{OH}+{\mathrm{OH}}^{-}+{\mathrm{Fe}}^{3+}$}

which, at the time the simulations were ran, could not be included due to the lack of appropriate chemical species, as well as time scale limitations in TOPAS‐nBio.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Monte Carlo study of the free radical yields in minibeam radiation therapy

Masilela

Prezado

2023

Medical Physics

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“…While our results and fits are so far only valid for low LET irradiation modalities, temperaturedependence will be further expanded to include higher LET modalities in future studies. For higher LET, the number of reactions must be expanded in order to properly simulate the radiolysis of pure liquid water (Baba et al 2021a, Baba et al 2021b, Hervé du Penhoat et al 2001 and a revision to the water dissociation schemes could be necessary due to the higher contribution of oxygen reactions (Shin et al 2021). The results obtained from this and past works (D-Kondo et al 2021, Ramos-Mendez et al 2021) show that at low LET modalities, there is no need to simulate oxygen related reactions due to the low contribution that this chemical specie gives to the whole chemical yields.…”

Section: Discussionmentioning

confidence: 99%

TOPAS-nBio simulation of temperature-dependent indirect DNA strand break yields

Ramos-Méndez¹,

Garcia-Garcia²,

Domínguez-Kondo³

et al. 2022

Phys. Med. Biol.

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Current Monte Carlo simulations of DNA damage have been reported only at ambient temperature. The aim of this work is to use TOPAS-nBio to simulate the yields of DNA single-strand breaks (SSBs) and double-strand breaks (DSBs) produced in plasmids under low-LET irradiation incorporating the effect of the temperature changes in the environment. A new feature was implemented in TOPAS-nBio to incorporate reaction rates used in the simulation of the chemical stage of water radiolysis as a function of temperature. The implemented feature was verified by simulating temperature-dependent G-values of chemical species in liquid water from 20oC to 90oC. For radiobiology applications, temperature-dependent SSB and DSB yields were calculated from 0oC to 42oC, the range of available published measured data. For that, supercoiled DNA plasmid dissolved in aerated solutions containing EDTA irradiated by Cobalt-60 gamma-rays were simulated. TOPAS-nBio well reproduced published temperature-dependent G-values in liquid water and the yields of SSB and DSB for the temperature range considered. For strand break simulations, the model shows that the yield of SSB and DSB increased linearly with the temperature at a rate of (2.94±0.17)x10–10 Gy–1Da–1 oC–1 (R2=0.99) and (0.13±0.01)x10–10 Gy–1Da–1 oC–1 (R2=0.99), respectively. The extended capability of TOPAS-nBio is a complementary tool to simulate realistic conditions for a large range of environmental temperatures, allowing refined investigations of the biological effects of radiation.

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“…Additional calculations included the energies, positions, and directions of the secondary electrons, as well as the transport of the secondary electrons. Multiple ionizations were not included [ 37 ]. The code was previously validated with experimental data such as radial dose experiments [ 38 ].…”

Section: Methodsmentioning

confidence: 99%

Simulation of Radiation-Induced DNA Damage and Protection by Histones Using the Code RITRACKS

Plante,

West,

Weeks

et al. 2024

BioTech

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(1) Background: DNA damage is of great importance in the understanding of the effects of ionizing radiation. Various types of DNA damage can result from exposure to ionizing radiation, with clustered types considered the most important for radiobiological effects. (2) Methods: The code RITRACKS (Relativistic Ion Tracks), a program that simulates stochastic radiation track structures, was used to simulate DNA damage by photons and ions spanning a broad range of linear energy transfer (LET) values. To perform these simulations, the transport code was modified to include cross sections for the interactions of ions or electrons with DNA and amino acids for ionizations, dissociative electron attachment, and elastic collisions. The radiochemistry simulations were performed using a step-by-step algorithm that follows the evolution of all particles in time, including reactions between radicals and DNA structures and amino acids. Furthermore, detailed DNA damage events, such as base pair positions, DNA fragment lengths, and fragment yields, were recorded. (3) Results: We report simulation results using photons and the ions 1H+, 4He2+, 12C6+, 16O8+, and 56Fe26+ at various energies, covering LET values from 0.3 to 164 keV/µm, and performed a comparison with other codes and experimental results. The results show evidence of DNA protection from damage at its points of contacts with histone proteins. (4) Conclusions: RITRACKS can provide a framework for studying DNA damage from a variety of ionizing radiation sources with detailed representations of DNA at the atomic scale, DNA-associated proteins, and resulting DNA damage events and statistics, enabling a broader range of future comparisons with experiments such as those based on DNA sequencing.

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A simulation-based study on water radiolysis species for 1H+, 4He2+, and 12C6+ ion beams with multiple ionization using Geant4-DNA

Cited by 5 publications

References 41 publications

Monte Carlo study of the free radical yields in minibeam radiation therapy

Monte Carlo study of the free radical yields in minibeam radiation therapy

TOPAS-nBio simulation of temperature-dependent indirect DNA strand break yields

Simulation of Radiation-Induced DNA Damage and Protection by Histones Using the Code RITRACKS

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