Validation of the spectral reconstruction of an electron beam by comparison with spectrum from Monte Carlo

Inverse reconstruction, one of the ways of calculating the energy spectrum of the central axis, has shown good results in various studies. Its validation, in the absence of the real spectrum and practicality, is usually done by comparing the PDP measured in the clinic, using the gamma index. The objective of the work is to validate the spectral reconstruction of a 6MeV electron beam from a Sinergy linear accelerator, by comparison with the spectrum derived from the Monte Carlo simulation of the accelerator head, as well as to carry out an analysis of its relationship with the validation by means of the clinically accepted gamma index criterion (>95% within 3% dose difference/3 mm in distance to agreement). The inverse reconstruction used Tikhonov regularization and generalized simulated annealing. Excellent agreement was observed between the PDP and the reconstructed dose profile (obtained from the reconstructed spectrum) and the measured and simulated PDPs (from the head simulation spectrum), as passage was >95% within of 1%/1mm and 2%/2mm for the PDPs and the dose profile, respectively. The simulated and reconstructed spectra presented similar shapes, coinciding in most probable energy and much of the low energy region. Despite serious discrepancies in the peak region, this was not reflected in clinically observable differences. In conclusion, it was verified that the reconstructed spectrum is close to one simulated by Monte Carlo, making it appropriate for clinical and research use.