New Geant4-DNA physics model for electron track-structure simulations in gold nanoparticles.

To develop a new Geant4-DNA physics model for electron track-structure simulations in gold nanoparticles (AuNPs) that overcomes important deficiencies of the current default model and is applicable over a broad energy range from 10 eV to 1 MeV.A model of the energy-loss-function of solid-Au with parameters optimized by optical data and self-consistency tests is presented and used to calculate inelastic cross sections using the relativistic plane wave Born approximation (RPWBA). Low-energy corrections for non-Born effects are included and a practical approximation to the Landau damping mechanism of plasmon decay is proposed that accounts for secondary electron production and facilitates its application to Monte Carlo (MC) track-structure simulations.

Verification of Geant4-DNA step-by-step-reaction-diffusion master equation model for long-term radiolysis simulation.

Purpose: This paper describes the verification of the step-by-step-reaction-diffusion Master Equation (SBS-RDME) model, implemented in Geant4-DNA, for long-term radiolysis simulations in the Fricke dosimeter.

Methods: Scaling for reaction rate constants due to the high acidity of the Fricke solution was applied. The secondary electrons generated by gamma irradiation from Co-60 were used as the radiation source for the simulations.

GANDALF: Generative ANsatz for DNA damage evALuation and Forecast. A neural network-based regression for estimating early DNA damage across micro-nano scales.

Purpose: This study aims to develop a comprehensive simulation framework to connect radiation effects from the microscopic to the nanoscopic scale.

Method: The process begins with a Geant4-DNA simulation based on the example "molecularDNA", producing a dataset of twelve different types of early DNA damages within an Escherichia coli (E. coli) bacterium, generated by proton irradiation at different kinetic energies, giving a nano-scale view of the particle-matter interaction.

Results of a Geant4 benchmarking study for bio-medical applications, performed with the G4-Med system.

Background: Geant4, a Monte Carlo Simulation Toolkit extensively used in bio-medical physics, is in continuous evolution to include newest research findings to improve its accuracy and to respond to the evolving needs of a very diverse user community. In 2014, the G4-Med benchmarking system was born from the effort of the Geant4 Medical Simulation Benchmarking Group, to benchmark and monitor the evolution of Geant4 for medical physics applications. The G4-Med system was first described in our Medical Physics Special Report published in 2021.

Analytic and Monte Carlo calculations of dose-mean lineal energy for 1 MeV-1 GeV protons with application to radiation protection quality factor.

Radiation quality for determining biological effects is commonly linked to the microdosimetric quantity lineal energy ( ) and to the dose-mean lineal energy ( ). Calculations of are typically performed by specialised Monte Carlo track-structure (MCTS) codes, which can be time-intensive. Thus, microdosimetry-based analytic models are potentially useful for practical calculations.

Investigating ultra-high dose rate water radiolysis using the Geant4-DNA toolkit and a Geant4 model of the Oriatron eRT6 electron linac.

Ultra-high dose rate FLASH radiotherapy, a promising cancer treatment approach, offers the potential to reduce healthy tissue damage during radiotherapy. As the mechanisms underlying this process remain unknown, several hypotheses have been proposed, including the altered production of radio-induced species under ultra-high dose rate (UHDR) conditions. This study explores realistic irradiation scenarios with various dose-per-pulse and investigates the role of pulse temporal structure.

Development of a novel computational technique to create DNA and cell geometrical models for Geant4-DNA.

Background: This study aimed to develop a novel human cell geometry for the Geant4-DNA simulation toolkit that explicitly incorporates all 23 chromosome pairs of the human cell. This approach contrasts with the existing, default human cell, geometrical model, which utilizes a continuous Hilbert curve.

Methods: A Python-based tool named "complexDNA" was developed to facilitate the design of both simple and complex DNA geometries.

Quantitative analysis of dose dependent DNA fragmentation in dry pBR322 plasmid using long read sequencing and Monte Carlo simulations.

Exposure to ionizing radiation can induce genetic aberrations via unrepaired DNA strand breaks. To investigate quantitatively the dose-effect relationship at the molecular level, we irradiated dry pBR322 plasmid DNA with 3 MeV protons and assessed fragmentation yields at different radiation doses using long-read sequencing from Oxford Nanopore Technologies. This technology applied to a reference DNA model revealed dose-dependent fragmentation, as evidenced by read length distributions, showing no discernible radiation sensitivity in specific genetic sequences.

In vitro validation of helium ion irradiations as a function of linear energy transfer in radioresistant human malignant cells.

Purpose: Based on considerable interest to enlarge the experimental database of radioresistant cells after their irradiation with helium ions, HTB140, MCF-7 and HTB177 human malignant cells are exposed to helium ion beams having different linear energy transfer (LET).

Materials And Methods: The cells are irradiated along the widened 62 MeV/u helium ion Bragg peak, providing LET of 4.9, 9.

"dsbandrepair" - An updated Geant4-DNA simulation tool for evaluating the radiation-induced DNA damage and its repair.

Purpose: Interdisciplinary scientific communities have shown large interest to achieve a mechanistic description of radiation-induced biological damage, aiming to predict biological results produced by different radiation quality exposures. Monte Carlo track-structure simulations are suitable and reliable for the study of early DNA damage induction used as input for assessing DNA damage. This study presents the most recent improvements of a Geant4-DNA simulation tool named "dsbandrepair".

Monte Carlo simulations of microdosimetry and radiolytic species production at long time post proton irradiation using GATE and Geant4-DNA.

Background: Radiobiological effectiveness of radiation in cancer treatment can be studied at different scales (molecular till organ scale) and different time post irradiation. The production of free radicals and reactive oxygen species during water radiolysis is particularly relevant to understand the fundamental mechanisms playing a role in observed biological outcomes. The development and validation of Monte Carlo tools integrating the simulation of physical, physico-chemical and chemical stages after radiation is very important to maintain with experiments.

Lithium inelastic cross-sections and their impact on micro and nano dosimetry of boron neutron capture.

To present a new set of lithium-ion cross-sections for (i) ionization and excitation processes down to 700 eV, and (ii) charge-exchange processes down to 1 keV u. To evaluate the impact of the use of these cross-sections on micro a nano dosimetric quantities in the context of boron neutron capture (BNC) applications/techniques.The Classical Trajectory Monte Carlo method was used to calculate Li ion charge-exchange cross sections in the energy range of 1 keV uto 10 MeV u.

In-silico calculations of DNA damage induced by α-particles in the Ra DaRT decay chain for a better understanding of the radiobiological effectiveness of this treatment.

Diffusing alpha-emitters radiation Therapy (DaRT) is an interstitial brachytherapy technique using Ra seeds. For accurate treatment planning a good understanding of the early DNA damage due to α-particles is required. Geant4-DNA was used to calculate the initial DNA damage and radiobiological effectiveness due to α-particles with linear energy transfer (LET) values in the range 57.

Geant4-DNA simulation of human cancer cells irradiation with helium ion beams.

Purpose: This study aimed to develop a computational environment for the accurate simulation of human cancer cell irradiation using Geant4-DNA. New cell geometrical models were developed and irradiated by alpha particle beams to induce DNA damage. The proposed approach may help further investigation of the benefits of external alpha irradiation therapy.

The general-purpose Geant4 Monte Carlo toolkit and its Geant4-DNA extension to investigate mechanisms underlying the FLASH effect in radiotherapy: Current status and challenges.

FLASH radiotherapy is a promising approach to cancer treatment that offers several advantages over conventional radiotherapy. With this novel technique, high doses of radiation are delivered in a short period of time, inducing the so-called FLASH effect - a phenomenon characterized by healthy tissue sparing without alteration of tumor control. The mechanisms behind the FLASH effect remain unknown.

Space radiation quality factor for Galactic Cosmic Rays and typical space mission scenarios using a microdosimetric approach.

Space radiation exposure from omnipresent Galactic Cosmic Rays (GCRs) in interplanetary space poses a serious carcinogenic risk to astronauts due to the-limited or absent-protective effect of the Earth's magnetosphere and, in particular, the terrestrial atmosphere. The radiation risk is directly influenced by the quality of the radiation, i.e.

Modeling of scavenging systems in water radiolysis with Geant4-DNA.

Purpose: This paper presents the capabilities of the Geant4-DNA Monte Carlo toolkit to simulate water radiolysis with scavengers using the step-by-step (SBS) or the independent reaction times (IRT) methods. It features two examples of application areas: (1) computing the escape yield of HO following a Co γ-irradiation and (2) computing the oxygen depletion in water irradiated with 1 MeV electrons.

Methods: To ease the implementation of the chemical stage in Geant4-DNA, we developed a user interface that helps define the chemical reactions and set the concentration of scavengers.

Simulation of DNA damage using Geant4-DNA: an overview of the "molecularDNA" example application.

Purpose: The scientific community shows great interest in the study of DNA damage induction, DNA damage repair, and the biological effects on cells and cellular systems after exposure to ionizing radiation. Several methods have been proposed so far to study these mechanisms using Monte Carlo simulations. This study outlines a Geant4-DNA example application, named "molecularDNA", publicly released in the 11.

Sub-keV corrections to binary encounter cross section models for electron ionization of liquid water with application to the Geant4-DNA Monte Carlo code.

Introduction: The electron ionization cross section of water is one of the most important input in Monte Carlo studies of cellular radiobiological effects. Analytical cross section models of the binary-encounter type have the potential of reducing simulation time and facilitate application to a variety of biological materials (other than water). The Binary-Encounter-Bethe (BEB) and Binary-Encounter-Dipole (BED) models of NIST are perhaps the most popular of such models giving reliable results for atoms and molecules in the gas-phase over a wide energy range.

Prediction of DNA rejoining kinetics and cell survival after proton irradiation for V79 cells using Geant4-DNA.

Purpose: Track structure Monte Carlo (MC) codes have achieved successful outcomes in the quantitative investigation of radiation-induced initial DNA damage. The aim of the present study is to extend a Geant4-DNA radiobiological application by incorporating a feature allowing for the prediction of DNA rejoining kinetics and corresponding cell surviving fraction along time after irradiation, for a Chinese hamster V79 cell line, which is one of the most popular and widely investigated cell lines in radiobiology.

Methods: We implemented the Two-Lesion Kinetics (TLK) model, originally proposed by Stewart, which allows for simulations to calculate residual DNA damage and surviving fraction along time via the number of initial DNA damage and its complexity as inputs.

Electron tracks simulation in water: Performance comparison between GPU CPU and the EUMED grid installation.

Purpose: We explored different technologies to minimize simulation time of the Monte-Carlo method for track generation following the Geant4-DNA processes for electrons in water.

Methods: A GPU software tool is developed for electron track simulations. A similar CPU version is also developed using the same collision models.

Intercomparison of nanodosimetric distributions in nitrogen simulated with Geant4 and PTra track structure codes.

To facilitate the use of Geant4-DNA for radiation transport simulations in micro- and nanodosimeters, which are physically operated with tissue-equivalent gases such as nitrogen (and propane), this work aims to extend the cross section data available in Geant4-DNA to include those of nitrogen for electron energies ranging from 1 MeV down to the ionisation threshold. To achieve this, interaction cross section data for nitrogen that have been used with the in-house PTB PTra track structure code have been implemented in the current state-of-the-art Geant4-DNA simulation toolkit. An intercomparison has been performed between the two codes to validate this implementation.