Journal article
Pitfalls in the beam modelling process of Monte Carlo calculations for proton pencil beam scanning.
- Winterhalter C Centre for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.
- Aitkenhead A Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK.
- Oxley D Centre for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.
- Richardson J Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK.
- Weber DC Centre for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.
- MacKay RI Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK.
- Lomax AJ Centre for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.
- Safai S Centre for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.
- 2020-02-01
Published in:
- The British journal of radiology. - 2020
Absorption, Radiation
Air
Bone and Bones
Brain
Humans
Monte Carlo Method
Proton Therapy
Radiation Dose Hypofractionation
Radiotherapy Dosage
Reproducibility of Results
Uncertainty
Water
English
OBJECTIVE
Monte Carlo (MC) simulations substantially improve the accuracy of predicted doses. This study aims to determine and quantify the uncertainties of setting up such a MC system.
METHODS
Doses simulated with two Geant4-based MC calculation codes, but independently tuned to the same beam data, have been compared. Different methods of MC modelling of a pre-absorber have been employed, either modifying the beam source parameters (descriptive) or adding the pre-absorber as a physical component (physical).
RESULTS
After the independent beam modelling of both systems in water (resulting in excellent range agreement) range differences of up to 3.6/4.8 mm (1.5% of total range) in bone/brain-like tissues were found, which resulted from the use of different mean water ionisation potentials during the energy tuning process. When repeating using a common definition of water, ranges in bone/brain agreed within 0.1 mm and gamma-analysis (global 1%,1mm) showed excellent agreement (>93%) for all patient fields. However, due to a lack of modelling of proton fluence loss in the descriptive pre-absorber, differences of 7% in absolute dose between the pre-absorber definitions were found.
CONCLUSION
This study quantifies the influence of using different water ionisation potentials during the MC beam modelling process. Furthermore, when using a descriptive pre-absorber model, additional Faraday cup or ionisation chamber measurements with pre-absorber are necessary.
ADVANCES IN KNOWLEDGE
This is the first study quantifying the uncertainties caused by the MC beam modelling process for proton pencil beam scanning, and a more detailed beam modelling process for MC simulations is proposed to minimise the influence of critical parameters.
Monte Carlo (MC) simulations substantially improve the accuracy of predicted doses. This study aims to determine and quantify the uncertainties of setting up such a MC system.
METHODS
Doses simulated with two Geant4-based MC calculation codes, but independently tuned to the same beam data, have been compared. Different methods of MC modelling of a pre-absorber have been employed, either modifying the beam source parameters (descriptive) or adding the pre-absorber as a physical component (physical).
RESULTS
After the independent beam modelling of both systems in water (resulting in excellent range agreement) range differences of up to 3.6/4.8 mm (1.5% of total range) in bone/brain-like tissues were found, which resulted from the use of different mean water ionisation potentials during the energy tuning process. When repeating using a common definition of water, ranges in bone/brain agreed within 0.1 mm and gamma-analysis (global 1%,1mm) showed excellent agreement (>93%) for all patient fields. However, due to a lack of modelling of proton fluence loss in the descriptive pre-absorber, differences of 7% in absolute dose between the pre-absorber definitions were found.
CONCLUSION
This study quantifies the influence of using different water ionisation potentials during the MC beam modelling process. Furthermore, when using a descriptive pre-absorber model, additional Faraday cup or ionisation chamber measurements with pre-absorber are necessary.
ADVANCES IN KNOWLEDGE
This is the first study quantifying the uncertainties caused by the MC beam modelling process for proton pencil beam scanning, and a more detailed beam modelling process for MC simulations is proposed to minimise the influence of critical parameters.
- Language
-
- English
- Open access status
- closed
- Identifiers
-
- DOI 10.1259/bjr.20190919
- PMID 32003576
- Persistent URL
- https://sonar.ch/global/documents/187224
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