X-ray phase contrast imaging with kilometer propagation distance within a meter

We introduce an x-ray imaging technique to facilitate dose-efficient propagation-based phase contrast imaging (PB-PCI) of large, centimeter-sized samples. The dose efficiency is realized by generating image contrast for low sampling frequencies, i.e., large pixel sizes, which would require propagation distances of tens to hundreds of meters in conventional PB-PCI. By magnifying the spatial frequency distribution of the diffracted wave field behind the sample, we strongly enhance the image contrast at short physical propagation distances, corresponding to kilometer-long distances. For this purpose, the wave field is demagnified by asymmetric Bragg crystal optics. Concomitantly, the crystal arrangement substantially reduces image blur caused by the finite x-ray source size. We demonstrate experimentally the significant increase in image contrast compared to conventional PB-PCI at the same short physical propagation distance. In combination with a subsequent Bragg magnifier, the method will allow for an even higher dose efficiency, rendering this technique a potential candidate for, e.g., low-dose (bio)medical diagnostics.