Modeling the head of PRIMUS linear accelerator for electron-mode at 10 MeV for different applicators

This study is to validate the utilization of Monte Carlo (MC) simulation to model the head of Primus linear accelerator, thereafter, using it to estimate the energy fluence distribution (EFD), the percentage depth dose (PDD), and beam profiles.

The BEAM_NRC code that is based on the EGS_NRC code has been used for modeling the linear accelerator head for 10 MeV electron beam with different applicator sizes (10 × 10, 15 × 15, and 20 × 20 cm² ). The phase space was acquired from BEAM_NRC at the end of each applicator and then used as an input file to DOSXYZ_NRC and BEAMDP to calculate the EFD, PDD, and beam profiles.

There were a good consistency between the outcomes of the MC simulation and measured PDD and off-axis dose profiles that performed in a water phantom for all applicators. The PDD for the applicators proved to be favorable as a direct comparison of R₁₀₀ , R₉₀ , R₈₀ , and R₅₀ yielded results of < 2 mm, while it was 6 mm in R₁₀₀ for the applicator 15 × 15 cm² . The discrepancies in the surface doses (<3%) showed a quick decline in the build-up region and differences reached 0% within the first 2.4 mm. For the beam profiles comparison, the differences ranged from 2% (2 mm) to 3% (6 mm) for all applicators.

Our examination demonstrated that the MC simulation by BEAM_NRC code was accurate in modeling the Primus linear accelerator head.