Simulation and experimental verification of prompt gamma-ray emissions during proton irradiation

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

Abstract

Irradiation with protons and light ions offers new possibilities for tumor therapy but has a strong need for novel imaging modalities for treatment verification. The development of new detector systems, which can provide an in vivo range assessment or dosimetry, requires an accurate knowledge of the secondary radiation field and reliable Monte Carlo simulations. This paper presents multiple measurements to characterize the prompt γ-ray emissions during proton irradiation and benchmarks the latest Geant4 code against the experimental findings. Within the scope of this work, the total photon yield for different target materials, the energy spectra as well as the γ-ray depth profile were assessed. Experiments were performed at the superconducting AGOR cyclotron at KVI-CART, University of Groningen. Properties of the γ-ray emissions were experimentally determined. The prompt γ-ray emissions were measured utilizing a conventional HPGe detector system (Clover) and quantitatively compared to simulations. With the selected physics list QGSP-BIC-HP, Geant4 strongly overestimates the photon yield in most cases, sometimes up to 50%. The shape of the spectrum and qualitative occurrence of discrete γ lines is reproduced accurately. A sliced phantom was designed to determine the depth profile of the photons. The position of the distal fall-off in the simulations agrees with the measurements, albeit the peak height is also overestimated. Hence, Geant4 simulations of prompt γ-ray emissions from irradiation with protons are currently far less reliable as compared to simulations of the electromagnetic processes. Deviations from experimental findings were observed and quantified. Although there has been a constant improvement of Geant4 in the hadronic sector, there is still a gap to close.

Details

Original languageEnglish
Pages (from-to)4197-4207
Number of pages11
JournalPhysics in medicine and biology
Volume60
Issue number10
Publication statusPublished - 21 May 2015
Peer-reviewedYes

External IDs

PubMed 25955576
ORCID /0000-0001-9023-3606/work/162845602

Keywords

Keywords

  • Geant4, Prompt gamma imaging, Proton therapy