Simulation of spread-out bragg peaks in proton beams using Geant4/TOPAS

Christian Velten, Wolfgang A. Tomé

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


The simulation of proton Spread-Out Bragg Peaks (SOBPs) was implemented using the Geant4-based TOPAS Monte Carlo software. Dynamic proton energy switching was implemented using TOPAS time features, while beam weights were calculated using an empirical power law formalism with Bragg peaks spaced by 0.5 mm. To find power parameters yielding flat SOBPs we sampled power parameters for maximum kinetic energies of 50 MeV to 250 MeV and SOBP widths of 15% to 40% of the depth of the distal SOBP end. Simulations were run in a 50 cm cubic water phantom using a uniform squared proton beam. Depth dose was scored along the central axis in a binned cylinder with 1 cm diameter in 2.5 mm increments. Power parameters yielding a flat SOBPs were found to vary with, both energy and SOBP width and differed significantly from previously reported values based on simulations with MCNPX.

Original languageEnglish (US)
Article number047001
JournalBiomedical Physics and Engineering Express
Issue number4
StatePublished - Jul 2020


  • Geant4
  • SOBP
  • proton therapy
  • simulation

ASJC Scopus subject areas

  • Biophysics
  • Bioengineering
  • Biomaterials
  • Physiology
  • Biomedical Engineering
  • Radiology Nuclear Medicine and imaging
  • Computer Science Applications
  • Health Informatics


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