Analytical and simulative investigations of moiré artefacts in Talbot-Lau X-ray imaging

Besides the well-known conventional X-ray attenuation image, Talbot-Lau X-ray imaging (TLXI) provides additional information about the small-angle scattering and refractive features of an object. In general, TLXI setups have to be mechanically robust, since already slight inaccuracies during the measurement process result in moire artefacts. This work derives moire artefacts as a result of phase-stepping inaccuracies. The dependency of these artefacts on the phase-stepping inaccuracies is mathematically derived by a Taylor series expansion and verified by a simulation. Among other things, it is shown that moire artefacts can be calculated by a weighted mean of phase-stepping position deviations to their target positions. These weighting factors vary for each image. Moire artefacts can even be affected by object features which are not displayed in the particular contrast. The findings of this work offer the possibility to develop advanced reconstruction algorithms which suppress moire artefacts in the reconstructed images. This reduces the method's susceptibility to setup component inaccuracies as well as external influences and hence facilitates TLXI for clinical practice. (C) 2017 Optical Society of America