Bolsa‐Ferruz, M; Palmans, H; Boersma, D; Stock, M; Grevillot, L (2021) Monte Carlo computation of 3D distributions of stopping power ratios in light ion beam therapy using GATE‐RTion. Medical Physics, 48 (5). pp. 2580-2591. ISSN 0094-2405

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Abstract

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 falloff) 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.

Item Type:	Article
Keywords:	carbon ion beam therapy, GATE, GATE-RTion, Geant4, light ion beam dosimetry, Monte Carlo, protontherapy, stopping power ratio
Subjects:	Ionising Radiation > Dosimetry
Divisions:	Medical, Marine & Nuclear
Identification number/DOI:	10.1002/mp.14726
Last Modified:	05 May 2023 13:39
URI:	https://eprintspublications.npl.co.uk/id/eprint/9231