Abstract
In order to quantify the scattered photon beam during X-ray radiography, deterministic particle transport algorithm uses the buildup factor (BUF) and the primary beam. However, from existing models describing such parameter for multilayer attenuators, we investigated three commonly used ones (Lin & Jiang, Kalos and Burke & Beck). Thus, the High Definition Reference Korean man (HDRK) was exposed to 150keV photon point source and particle histories were computed comprising the attenuation of the primary beam and the scattered beam contribution. For that purpose, we developed an in-house C++ based program to store projected phantom images, at an imaging detector distant with 1m far from the source, with possible choice between concerned BUF models. The thorax part only of the HDRK man was irradiated and based on specific Geometric Progression (GP) fitting parameters, Compton and total attenuation coefficients and equivalent atomic number of 25 organs, computations were carried out. We found a close image similarity for both models of Lin & Jiang and Kalos (SSIM=0.94). Also, the projected image resolution was ordered in the following way from better to worst: Lin & Jiang, Kalos and Burke & Beck. A correct model choice will be of great interest to the large community of radiation physicists, in general, and to medical imaging, teletherapy and brachytherapy physicists, in particular, since multilayer BUF parameters are the key parameter for point kernel calculations.

Key words: Buildup Factor; Multilayer; Human Tissues ; Radiography; HDRK man;