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Title: Technical Note: Improvements in GEANT4 energy-loss model and the effect on low-energy electron transport in liquid water

Purpose: The GEANT4-DNA physics models are upgraded by a more accurate set of electron cross sections for ionization and excitation in liquid water. The impact of the new developments on low-energy electron transport simulations by the GEANT4 Monte Carlo toolkit is examined for improving its performance in dosimetry applications at the subcellular and nanometer level. Methods: The authors provide an algorithm for an improved implementation of the Emfietzoglou model dielectric response function of liquid water used in the GEANT4-DNA existing model. The algorithm redistributes the imaginary part of the dielectric function to ensure a physically motivated behavior at the binding energies, while retaining all the advantages of the original formulation, e.g., the analytic properties and the fulfillment of the f-sum-rule. In addition, refinements in the exchange and perturbation corrections to the Born approximation used in the GEANT4-DNA existing model are also made. Results: The new ionization and excitation cross sections are significantly different from those of the GEANT4-DNA existing model. In particular, excitations are strongly enhanced relative to ionizations, resulting in higher W-values and less diffusive dose-point-kernels at sub-keV electron energies. Conclusions: An improved energy-loss model for the excitation and ionization of liquid water by low-energy electrons has been implementedmore » in GEANT4-DNA. The suspiciously low W-values and the unphysical long tail in the dose-point-kernel have been corrected owing to a different partitioning of the dielectric function.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Medical Physics Laboratory, University of Ioannina Medical School, Ioannina 45110 (Greece)
  2. Centre d’Etudes Nucléaires de Bordeaux-Gradignan, CENBG, Chemin du Solarium, Université de Bordeaux, Gradignan 33175, France and Centre d’Etudes Nucléaires de Bordeaux-Gradignan, CENBG, Chemin du Solarium, CNRS/IN2P3, Gradignan 33175 (France)
  3. Department of Physics, Faculty of Sciences, Saint Joseph University, Mkalles, Beirut (Lebanon)
Publication Date:
OSTI Identifier:
22413606
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 7; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; BORN APPROXIMATION; COMPUTERIZED SIMULATION; ELECTRONS; ENERGY LOSSES; EXCITATION; LIQUIDS; MONTE CARLO METHOD; RESPONSE FUNCTIONS; WATER