Abstract
This work aims to characterize mammographic x-ray beams incident and transmitted by breast phantoms (from 0 to 45 mm) composed from known proportion of glandular and adipose tissue-equivalent materials. This study was performed for mammographic x-ray beams generated by a mammography equipment using different target/filter combinations (Mo/Mo, Mo/Rh and W/Rh). It was studied the modification of spectra shape of the beams transmitted through different thicknesses of these materials. It was also evaluated the penetrability of these transmitted beams by its correlations to the HVL, which were experimentally estimated and derived from the x-ray spectra measured using a spectrometry system with a CdTe detector. The x-ray spectra transmitted by the phantom with higher density presented lower intensity than those transmitted by those with lower density, as expected. The differences between the HVL values derived from the spectra and those estimated using air kerma measurements are lesser than 6% for about 88% of the spectra measured in this work. The expected spectra variations with phantom thickness, revealed by the measured transmitted x-ray spectra, were also confirmed by HVL measurements and agree with the estimated attenuation curves.The motivation of the study was related to the robustness of the spectra as a descriptor of radiation beams and the possibility of using these transmitted spectra for dose assessment related to mammographic procedures. We can conclude that developed method is able to characterize mammographic x-ray beams making it possible the use of this kind of data for dose assessment in mammography.
Highlights
Transition metal (TM) compounds play a major role in condensed matter physics and materials science
The simplest 3d transition metal oxides (TMOs), e.g. MnO, CoO, and NiO have allowed us to reach the current understanding of the electronic structure of these materials and their insulating bandgap either as Mott-Hubbard or as charge-transfer (CT) insulators, as stated by the Zaanen-Sawatzky-Allen (ZSA) diagram [25]
It took more than two decades to have a direct experimental proof of the ZSA theory and it came from a combined experiment of X-ray absorption (XAS) and emission (XES) spectroscopies on the most ionic TM compounds, the difluorides TMF2 (Cr-Zn) at the TM L2,3 and F K edges [18]
Summary
Transition metal (TM) compounds play a major role in condensed matter physics and materials science. The electronic band structure of NiF2 has been studied using the full potential linearized augmented plane wave (LAPW) method, with the exchange and correlation effects treated in the local spin-density approximation (LSDA) [6] This calculation correctly predicts the insulating ground state in NiF2 but the bandgap is largely underestimated as compared to the experimental determination obtained from soft X-ray spectroscopies [18]. It was used to produce 3-D nanoporous flexible electrodes for commercial applications [24] It shows potential as a cathode material for rechargeable Li ion batteries [16, 26] which in a NiO-doped NiF2-C version of the previous cathodes was investigated by hard X-ray absorption spectroscopy [17]. In RIXS at the nickel L2,3 edges, the metal emission that follows resonant excitation of a 2p electron produces d-excited states of the ground configuration
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