A Monte Carlo simulation method for reconstruction of accelerator based on verified 6 MV X-ray phase-space and energy spectrum information

Abstract

Objective To establish a novel Monte Carlo simulation method for reconstruction of medical accelerator model and X-ray energy spectrum based on IAEA Varian 6 MV X-ray phase-space file and photon energy spectrum of the target accelerator. Methods The verified 6 MV X-ray phase-space files were preprocessed to elevate the energy of each particle. Particles were saved in different Phase-Space-Let (PSL) files according to their position and energy, yielding an initial photon energy spectrum for Monte Carlo simulation of accelerator under an initial target energy. The initial photon energy spectrum was fit to a photon energy spectrum of an accelerator (Elekta Precise 10 MV X-ray accelerator) under an unknown target energy to yield a fitting coefficient, which was the weight of each PSL. Finally, an accelerator model under an unknown target energy was reconstructed using the initial PSL files and the weight information. The percentage depth dose (PDD) distribution was calculated in different square open fields. The effectiveness of this method was verified using one dimensional gamma passing rate. Results The peak position and overall distribution of the reconstructed 10 MV photon energy spectrum were in accordance with those of the verified 10 MV photon energy spectrum. The PDD calculated from the reconstructed 10 MV accelerator model agreed well with the measured PDD. The one-dimensional gamma passing rate was above 96%(1%/1 mm, threshold=0%). Conclusion The Monte Carlo reconstruction method proposed in this study is reliable, accurate, and effective. Key words: X-ray energy spectrum; Linac head beamreconstruction; Phase-Space-Let files; Monte Carlo simulation