Comparison of the MCNP4C and BEAMnrc Monte Carlo codes when simulating different electron energies of a Neptun 10pc linear accelerator

Given the weaknesses of analytical electron dose calculation algorithms and the shorter Monte Carlo simulation time for electrons compared to photons, electron Monte Carlo is a useful practical tool in treatment planning. To our knowledge, no electron simulation work has been published on the Neptun 10pc linac (Zdaj, Poland). The purpose of this study was to simulate this linac’s 6, 8 and 10 MeV electron beams using the MCNP4C and BEAMnrc Monte Carlo codes and compare their calculations with measurements. Method: The ITS energy-indexing algorithm was used in MCNP4C. For BEAMnrc, phase-space files stored for realistic electron beams were used as input into DOSXYZnrc Monte Carlo code. Central-axis percentage depth doses (PDDs) and off-axis dose profiles at 6,8 and 10 MeV were simulated and measured using a P-type electron diode detector in a water phantom. Simulation parameters were first fine-tuned by comparing the calculated PDD curves and dose profiles at the 10×10 cm2 field size with measurements and four other field sizes were subsequently compared. Results: The best simulated 6, 8 and 10 MeV electron beams had Gaussian distributions with full-width-at-half-maximum values of 1.2, 1.6 and 2.0 MeV respectively. For both codes, agreement between measured and calculated doses was within 2%/2mm and the AAPM TG-53 acceptance criteria at all energies. BEAMnrc ran at least six times faster than MCNP4C. Conclusion: Despite the differences in head and applicator geometry between the Neptun and other linacs, its successful simulation is demonstrated. Both simulated models are reliable for electron dose calculation in water. BEAMnrc’s faster calculation and ease of head geometry set-up make it a more practical option while MCNP4C offers more flexibility in defining complex geometries.

کلیدواژه ها:

Monte Carlo simulation ، MCNP ، BEAMnrc ، electron radiotherapy