Monte Carlo calculated beam quality correction factors for high energy electron beams

• Published in: Physica medica Vol. 117; p. 103179
• Main Authors: Alissa, Mohamad, Zink, Klemens, Röser, Arnd, Flatten, Veronika, Schoenfeld, Andreas A., Czarnecki, Damian
• Format: Journal Article
• Language: English
• Published: Italy Elsevier Ltd 01.01.2024
• Subjects: Beam quality correction factor; Dosimetry; Electrons; High energy electron beams; Ionization chamber; Monte Carlo Method; Monte Carlo simulation; Phenylpropionates; Radiometry - methods; Relative Biological Effectiveness; Water; Beam quality correction factor; Ionization chamber; Dosimetry; High energy electron beams; Monte Carlo simulation
• ISSN: 1120-1797; 1724-191X
• DOI: 10.1016/j.ejmp.2023.103179

As the dosimetry protocol TRS 398 is being revised and the ICRU report 90 provides new recommendations for density correction as well as the mean ionization energies of water and graphite, updated beam quality correction factors kQ are calculated for reference dosimetry in electron beams and for independent validation of previously determined values. Monte Carlo simulations have been performed using EGSnrc to calculate the absorbed dose to water and the dose to the active volumes of ionization chambers SNC600c, SNC125c and SNC350p (all Sun Nuclear, A Mirion Medical Company, Melbourne, FL). Realistic clinical electron beam spectra were used to cover the entire energy range of therapeutic electron accelerators. The Monte Carlo simulations were validated by measurements on a clinical linear accelerator. With regards to the cylindrical chambers, the simulations were performed according to the setup recommendations of TRS 398 and AAPM TG 51, i.e. with and without consideration of a reference point shift by rcav/2. kQ values as a function of the respective beam quality specifier R50 were fitted by recommended equations for electron beam dosimetry in the range of 5 MeV to 18 MeV. The fitting curves to the calculated values showed a root mean square deviation between 0.0016 and 0.0024. Electron beam quality correction factors kQ were calculated by Monte Carlo simulations for the cylindrical ionization chambers SNC600c and SNC125c as well as the plane parallel ionization chamber SNC350p to provide updated data for the TRS 398 and TG 51 dosimetry protocols. •Clinical electron beam dosimetry is based on ionization chambers.•For absolute dose measurements, beam quality correction factors kQ must be used.•The kQ values calculated using Monte Carlo simulations were verified by additional measurements.•For the first time, kQ values for three commonly used ionization chambers are provided for electron beam dosimetry.