X-ray imaging approaches that are sensitive to phase effects can capture weakly-attenuating sample features that are not easily seen with conventional x-ray imaging. One of the most recently-developed approaches to capturing phase effects is single-grid or speckle-tracking phase contrast x-ray imaging. This approach directly resolves a reference pattern, created by illuminating either a grid [1, 2] or a piece of sandpaper [3, 4], and looks at sample-induced distortions to that reference pattern to extract phase effects and/or dark-field effects. At the x-ray energies used at synchrotron imaging beamlines, these directly-resolved distortions are typically in the micron range, so the approach is well-suited to microscopy with a field of view close to 1mm across. This method of phase contrast imaging presents a distinct advantage for high-speed or time-resolved imaging, in that only one sample exposure is required to extract attenuation, phase and dark-field effects. Other advantages include a sensitivity to a slowly-changing sample thickness/density via differential contrast, and the ability to simultaneously capture differential contrast in both directions within the image plane (e.g. x and y) [5].
This presentation will describe recent developments in single-grid/speckle imaging, including computational approaches to the extraction of contrast modalities, biomedical applications of the technique [6], the extension to single-exposure, single-energy material segmentation [7], and a theoretical model to describe the combined attenuation, phase and dark-field effects [8, 9].