Estimating Transmission Curves of Primary X-Ray Beams Used in Diagnostic Radiology

This paper shows the comparison among experimental, theoretical published data and data generated by the Geant4 toolkit to determine X-ray transmission curves in an energy range suitable for radiology as well a study of the influence of spectra and shielding composition on transmission data. The objectives of this work were: to compare the differences on transmission data considering different shielding material composition, to validate the application for Geant4 and to calculate transmission curves for new material based on the proposed methodology. Transmission curves and fitting equations for lead, concrete, barited concrete and barited mortar were obtained as a function of shielding thickness and X-ray polychromatic spectra. The simulated transmission curves for lead showed to be statistically the same when compared to published reference. Good agreement was calculated between the experimental data and the data simulated using Geant4. For the other composite materials no comparable reference data is available, but the spread in the transmission values is below 10% for the range of the thicknesses used in real shielding. The results showed that changes in composition for the studied materials can have some impact on the transmission data. The X-ray transmission was sensitive to changes in the incoming beam energy spectra for a fixed acceleration voltage. The simulation application developed in this work can be used, associated to a shielding composition elemental analysis, to customize transmission curves for different composite materials and X-ray spectra.