Despite the benefits of mammography investigations, some studies have shown that X-ray exposure from the mammography screening itself can statistically cause breast cancer in a small fraction of women. Therefore, a dose reduction in mammography is desirable. At the same time, there is a demand for a higher spatial resolution in mammographic imaging. The most promising way to achieve these goals is the use of advanced photon-processing semiconductor X-ray detectors with optimum sensor materials. This study addresses the investigation of the optimum semiconductor sensor material for mammography in combination with the photon-processing detector Medipix3RX. The influence of K-shell fluorescence from the sensor material on the achievable contrast-to-noise ratio is investigated, as well as the attenuation efficiency. The three different sensor materials, CdTe, GaAs, and Si are studied, showing advances of CdTe-sensors for mammography. Furthermore, a comparison of the contrast-to-noise ratio between a clinical Se-detector and Medipix3RX detectors with Si-and CdTe-sensors is shown using a self-produced mammography phantom that is based on real human tissue.

Pixelated photon counting semiconductor X-ray detectors like the Medipix feature adjustable energy thresholds allowing selective counting of photons of a specified energy. This development permits for energy selective X-ray imaging with advanced material information. Furthermore the photon counting function principle of these detectors allows X-ray imaging with reduced noise, providing contrast improvement in low contrast objects. The aim of this study is to analyze the behavior of the new Medipix3 detector, especially regarding flatfield correction for X-ray imaging applications. First high resolution low contrast X-ray images and energy selective X-ray images acquired with the Medipix3 detector are presented as well in this paper.

We show that the conduction band structure of dilute ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{\mathrm{As}}_{1-y}{\mathrm{N}}_y$ with $x⩽0.37$ and $y⩽0.04$ can be described consistently by the experimentally motivated band anticrossing model. The interband transition energies $E_{-}$ , $E_{-}+{\Delta }_0$ , and $E_{+}$ have been derived from a full line shape fit to photomodulated reflectance (PR) spectra recorded at room temperature. The PR data were taken (a) from a series of ${\mathrm{Al}}_{0.06}{\mathrm{Ga}}_{0.94}{\mathrm{As}}_{1-y}{\mathrm{N}}_y$ samples with $y⩽0.04$ and (b) from a set of ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{\mathrm{As}}_{0.99}{\mathrm{N}}_{0.01}$ layers with $x⩽0.37$ . The latter series covers the range of Al concentrations where the ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ band gap energy $E_{\mathrm{M}}$ is expected to cross the nitrogen-induced energy level $E_{\mathrm{N}}$ . The resulting nitrogen- and Al-concentration dependent interband transition energies are described by the band anticrossing model using a matrix element for the coupling between the nitrogen-induced states and the extend lowest conduction band states of $C_{\mathrm{MN}}=2.32\mathrm{eV}$ and a nitrogen level energy $E_{\mathrm{N}}=(1.625+0.069x)\mathrm{eV}$ , the latter measured with respect to the GaAs valence band edge.