Dynamic flat field correction in edge illumination imaging

Edge Illumination (EI) X-ray phase contrast imaging (XPCI) is a promising technique that, next to conventional attenuation contrast, provides phase contrast and dark field contrast. Opposed to conventional x-ray imaging though, EI-XPCI is more vulnerable to focal spot drifts, leading to intensity changes in the acquired projections. As a result, attenuation, phase, and dark field contrast parameters that are estimated from these projections also suffer from these variations. In this work, through accurate phase contrast simulations using the recently developed CAD-ASTRA toolbox, we study the effect of the focal spot drifts on EI-XPCI parameter estimation. These variations are then modeled by computing eigen flat fields (EFFs). Subsequently, the EFFs are used to normalize the projections corresponding to each phase step of an EI-XPCI acquisition. Results indicate that dynamic flat field correction (FFC) based on EFFs outperforms conventional FFC in EI-XPCI.