Monte Carlo method for the photon attenuation by filters in conventional radiography

In this paper we have analysed the photon attenuation of the components of X-ray spectra used in diagnostic radiology carried out by the most useful filters. First, the behaviour of monoenergetic beams has been studied and the results have been used to analyze the modifications that the filters produce in given experimental spectra. These spectra have been taken from the bibliography and correspond to X-rays beams produced by accelerating voltages of 60, 80, 90 y 125 kV and filtered by 2.5 mm of aluminium and 1m of air. The effect of aluminium and copper filters of various thicknesses was analysed. Monte Carlo simulation code PENELOPE has been used to perform the radiation transport. We have investigated in detail the dependence of the attenuation of the primary beam with the initial energy and the fraction of initial photons which reach the patient. The results show that the filters have a remarkable impact on the spectral distribution, being efficient in removing the low energy photons of the Bremsstrahlung spectrum. Therefore when the spectrum impinging on the patient is strongly modelled by the filters and these dose imparted to the patient is reduced. (Author)