Energy response and proton range measurement with EBT3 film simulated by Geant4 / 中国辐射卫生

ABSTRACT

@#<b>Objective</b> To calculate the energy dependence of absorbed dose in EBT3 film, and to reveal the error in the measurement of proton absorbed dose by EBT3 film. <b>Methods</b> Beam energy was gradually increased in the clinical photon and proton energy ranges. Geant4 was used to calculate the difference in absorbed dose between EBT3 film and the same volume of water. The results were compared with the theoretical values. <b>Results</b> For photons and protons, the thresholds for absorbed dose with energy dependence were 100 keV and 11 MeV, respectively. The energy dependence was consistent with the theoretical values when the photon and proton energies were higher than the corresponding thresholds, and irrelevant to the theoretical values when energies were lower than the thresholds. The differences between the proton Bragg peak and 50% dose point and the actual positions were less than 1%. <b>Conclusions</b> For protons and photons with high energy, the energy dependence of absorbed dose in EBT3 film is negligible. For protons and photons with low energy, EBT3 film shows very different energy dependence of absorbed dose, which should be taken into consideration. The proton Bragg peak and 50% dose point measured by EBT3 film are basically the same as the actual positions.