Spectral phase-contrast X-ray imaging with high-resolution detectors

X-ray phase contrast imaging (XPCI) records phase shifts in X-rays as they pass through matter, enabling the distinction of features, such as soft tissues, that have low contrast in conventional absorption-based methods. Phase contrast beam tracking technique uses an absorbing mask to shape the X-ray beam into an array of beamlets before they reach the detector. Analyzing these beamlets provides information on X-ray absorption, refraction (differential phase), and ultra-small-angle scattering. In XPCI, mask visibility is typically defined as the ratio between the standard deviation and the mean value measured from a chosen region in the mask image. The primary focus of this study is to investigate the influence of detector spatial resolution on mask visibility. Three different scintillator-coupled scientific CMOS detectors, with varying pixel sizes and scintillator thicknesses, were tested to highlight the difference in response in terms of visibility from a given mask. Additionally, the impact of visibility on the image quality in refraction images was investigated through a wave optics simulation. The results showcase the trends of contrast and signal-to-noise ratio values as a function of mask visibility. This work is part of the development of a novel setup for combined X-ray Spectral Imaging (XSI) and XPCI undertaken by INFN's Sphere-X project implemented at the Elettra Sincrotrone Trieste.