Semiempirical adjustments to bremsstrahlung model for x-ray production from CT tubes

In this study, we carried out an analytical description for the x-ray bremsstrahlung spectrum generated by a Toshiba CT Scanner installed in a Public Hospital in Sao Jose, Brazil. The goal is to obtain simple empirical equations that predict the photon yield in good agreement with measured results. The new points developed by this study are: (a) the use of recommended and more accurate databases of stopping power for electrons by thick materials; (b) a new normalization procedure is proposed to impose the energy conservation between total photon emitting and total electron bremsstrahlung energy loss; (c) a new approach to radiation self-attenuation. A complete database of stopping power for electrons by thick materials is available from National Institute of Standards and Technology Physics Reference Data. These data have an uncertainty of 5% in medical x-ray energy levels. These points are improved with respect to previous models, which use many complex empirical equations to predict electron and self-attenuation behaviors. The electron energy as a function of the depth penetrated into the thick target is described through the experimental electronic energy loss. The penetration function has been found to be similar to the Thomson-Whiddington equation but with different exponential dependence.