Article

Comparison of GEANT4 very low energy cross section models with experimental data in water

Université Bordeaux 1, CNRS/IN2P3, Centre d'Etudes Nucléaires de Bordeaux-Gradignan, CENBG, Chemin du Solarium, BP 120, 33175 Gradignan, France.
Medical Physics (Impact Factor: 3.01). 09/2010; 37(9):4692-708. DOI: 10.1118/1.3476457
Source: PubMed

ABSTRACT The GEANT4 general-purpose Monte Carlo simulation toolkit is able to simulate physical interaction processes of electrons, hydrogen and helium atoms with charge states (H0, H+) and (He0, He+, He2+), respectively, in liquid water, the main component of biological systems, down to the electron volt regime and the submicrometer scale, providing GEANT4 users with the so-called "GEANT4-DNA" physics models suitable for microdosimetry simulation applications. The corresponding software has been recently re-engineered in order to provide GEANT4 users with a coherent and unique approach to the simulation of electromagnetic interactions within the GEANT4 toolkit framework (since GEANT4 version 9.3 beta). This work presents a quantitative comparison of these physics models with a collection of experimental data in water collected from the literature.
An evaluation of the closeness between the total and differential cross section models available in the GEANT4 toolkit for microdosimetry and experimental reference data is performed using a dedicated statistical toolkit that includes the Kolmogorov-Smirnov statistical test. The authors used experimental data acquired in water vapor as direct measurements in the liquid phase are not yet available in the literature. Comparisons with several recommendations are also presented.
The authors have assessed the compatibility of experimental data with GEANT4 microdosimetry models by means of quantitative methods. The results show that microdosimetric measurements in liquid water are necessary to assess quantitatively the validity of the software implementation for the liquid water phase. Nevertheless, a comparison with existing experimental data in water vapor provides a qualitative appreciation of the plausibility of the simulation models. The existing reference data themselves should undergo a critical interpretation and selection, as some of the series exhibit significant deviations from each other.
The GEANT4-DNA physics models available in the GEANT4 toolkit have been compared in this article to available experimental data in the water vapor phase as well as to several published recommendations on the mass stopping power. These models represent a first step in the extension of the GEANT4 Monte Carlo toolkit to the simulation of biological effects of ionizing radiation.

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    • ") with the Geant4 - DNA ( Incerti et al . , 2010 ) low energy extension is being employed in the present study . The physical models were the default models provided by G4EmDNAPhysics ( Incerti et al . , 2010 ) . The transport cut - off was 7 . 4 eV . The Auger effect in atomic de - excitation was activated . The spectra of radionuclides were taken from ( Howell , 1992 ) and en - ergies and yields are presented in Table 1 . In our simulations we used these values as initial energies according to the yield of Fig . 2 . ( a ) Cell geometry of "
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    ABSTRACT: Geant4-DNA is used to calculate S-values for different subcellular distributions of low-energy electron sources in various cell geometries. Calculations of cellular S-values for monoenergetic electron sources with energy from 1 to 100keV and the Auger-electron emitting radionuclides Tc-99m, In-111, and I-125 have been made using the Geant4 Monte Carlo toolkit. The Geant4-DNA low-energy extension is employed for simulating collision-by-collision the complete slowing-down of electron tracks (down to 8eV) in liquid water, used as a surrogate of human cells. The effect of cell geometry on S-values is examined by simulating electron tracks within different cell geometries, namely, a spherical, two ellipsoidal, and an irregular shape, all having equal cellular and nuclear volumes. Algorithms for randomly sampling the volume of the nucleus, cytoplasm, surface, and whole cell for each cell phantom are presented. Differences between Geant4-DNA and MIRD database up to 50% were found, although, for the present radionuclides, they mostly remain below 10%. For most source-target combinations the S-values for the spherical cell geometry were found to be within 20% of those for the ellipsoidal cell geometries, with a maximum deviation of 32%. Differences between the spherical and irregular geometries are generally larger reaching 100-300%. Most sensitive to the cell geometry is the absorbed dose to the nucleus when the source is localized on the cell surface. Interestingly, two published AAPM spectra for I-125 yield noticeable differences (up to 19%) in cellular S-values. Monte Carlo simulations of cellular S-values with Geant4-DNA reveal that, for the examined radionuclides, the widely used approximation of spherical cells is reasonably accurate (within 20-30%) even for ellipsoidal geometries. For irregular cell geometries the spherical approximation should be used with caution because, as in the present example, it may lead to erroneous results for the nuclear dose for the commonly encountered situation where the source is localized to the cell surface. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 06/2015; 104:113-123. DOI:10.1016/j.apradiso.2015.06.027 · 1.06 Impact Factor
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    • "In their paper, the authors have tested many hypotheses and suggested that the disagreement was essentially due to the influence of the number of steps in the scoring shells on the scattering angle of the electrons as confirmed by Schaart et al. (2002). In this context, we have tested the influence of elastic scattering modeling on the energy scoring by using two different theoretical models, either the screened Rutherford model or the partial-wave based approach proposed by Champion et al. (2009) and recently implemented into the GEANT4-DNA code (Incerti et al., 2010). Thus, for 10 keV electrons , we have observed that the DPK (not shown here) obtained when describing the elastic scattering process via the screened Rutherford model was in strong disagreement with that provided by the partial-wave model with particularly a shift of the peak position as well as an overestimated magnitude. "
    Dataset: ARI2014a
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    • "In their paper, the authors have tested many hypotheses and suggested that the disagreement was essentially due to the influence of the number of steps in the scoring shells on the scattering angle of the electrons as confirmed by Schaart et al. (2002). In this context, we have tested the influence of elastic scattering modeling on the energy scoring by using two different theoretical models, either the screened Rutherford model or the partial-wave based approach proposed by Champion et al. (2009) and recently implemented into the GEANT4-DNA code (Incerti et al., 2010). Thus, for 10 keV electrons , we have observed that the DPK (not shown here) obtained when describing the elastic scattering process via the screened Rutherford model was in strong disagreement with that provided by the partial-wave model with particularly a shift of the peak position as well as an overestimated magnitude. "
    Dataset: ARI2014a
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