Monte Carlo computation of 3D distributions of stopping power ratios in light ion beam therapy using GATE-RTion

Marta Bolsa-Ferruz*, Hugo Palmans, David Boersma, Markus Stock, Loïc Grevillot

*Corresponding author for this work

Research output: Journal article (peer-reviewed)Journal article

5 Citations (Scopus)


Purpose: This paper presents a novel method for the calculation of three-dimensional (3D) Bragg–Gray water-to-detector stopping power ratio (sw,det) distributions for proton and carbon ion beams. Methods: Contrary to previously published fluence-based calculations of the stopping power ratio, the sw,det calculation method used in this work is based on the specific way GATE/Geant4 scores the energy deposition. It only requires the use of the so-called DoseActor, as available in GATE, for the calculation of the sw,det at any point of a 3D dose distribution. The simulations are performed using GATE-RTion v1.0, a dedicated GATE release that was validated for the clinical use in light ion beam therapy. Results: The Bragg–Gray water-to-air stopping power ratio (sw,air) was calculated for monoenergetic proton and carbon ion beams with the default stopping power data in GATE-RTion v1.0 and the new ICRU90 recommendation. The sw,air differences between the use of the default and the ICRU90 configuration were 0.6% and 5.4% at the physical range (R80 — 80% dose level in the distal dose fall-off) for a 70 MeV proton beam and a 120 MeV/u carbon ion beam, respectively. For protons, the sw,det results for lithium fluoride, silicon, gadolinium oxysulfide, and the active layer material of EBT2 (radiochromic film) were compared with the literature and a reasonable agreement was found. For a real patient treatment plan, the 3D distributions of sw,det in proton beams were calculated. Conclusions: Our method was validated by comparison with available literature data. Its equivalence with Bragg–Gray cavity theory was demonstrated mathematically. The capability of GATE-RTion v1.0 for the sw,det calculation at any point of a 3D dose distribution for simple and complex proton and carbon ion plans was presented.

Original languageEnglish
Pages (from-to)2580-2591
Number of pages12
JournalMedical Physics
Issue number5
Publication statusPublished - May 2021
Externally publishedYes


  • carbon ion beam therapy
  • GATE
  • GATE-RTion
  • Geant4
  • light ion beam dosimetry
  • Monte Carlo
  • protontherapy
  • stopping power ratio
  • Protons
  • Radiotherapy Dosage
  • Humans
  • Ions
  • Proton Therapy
  • Radiometry
  • Monte Carlo Method

ASJC Scopus subject areas

  • Biophysics
  • Radiology, Nuclear Medicine and Imaging


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