Assessment of Gafchromic Film Dosimetry for Low-Energy Proton Beams Using Geant4 Monte Carlo Simulations
Abstract
Purpose
Accurate dosimetry of low-energy proton beams (2–4 MeV) for radiobiological experiments is challenging due to beam modification in air. This study extends previous work on Gafchromic HD-V2 film dosimetry by quantitatively validating experimental dose measurements using Geant4 Monte Carlo simulations.
Methods
Gafchromic HD-V2 films were irradiated with 2–4 MeV proton beams at the ECU Accelerator Laboratory under vacuum conditions at a fixed distance and under in-air conditions at varying distances (13, 17, and 24 mm) from the beamline exit window. Calibration curves were obtained by correlating film gray values with delivered dose. Lateral dose profiles were extracted from the irradiated films using radial line analysis across the 1-inch film diameter. Geant4 simulations were performed using a geometry matching the experimental setup, and dose distributions were scored in regions corresponding to the film active layer. Dose values at the maximum, 50%, and 13% relative dose levels were extracted from the lateral profiles to quantitatively compare experimental film measurements with Geant4 simulations.
Results
Calibrated Gafchromic HD-V2 film measurements showed good agreement with Geant4 Monte Carlo simulations across all investigated proton energies and distances from the exit window. Agreement at the 50% and 13% relative dose confirmed consistency in the central and low-dose regions of the lateral beam profile, while maximum dose comparisons demonstrated accurate reproduction of peak dose characteristics. Lateral dose profile comparisons further showed agreement in profile shape and dose fall-off behavior.
Conclusion
Calibrated Gafchromic HD-V2 film dosimetry was validated against Geant4 Monte Carlo simulations, demonstrating accurate characterization of low-energy proton beam dose distributions for radiobiological applications.