When we think of X-ray imaging, we imagine a photon view as particles are absorbed or scattered in materials. This provides the imaging contrast in many important applications such as dental, chest X-rays, airport scanners. The application of X-ray diffraction gratings enables additional contrast modalities using conventional off-the-shelf X-ray sources. Specifically, the differential phase contrast mode can provide direct access to electron density, and the dark field (fringe visibility) contrast can give texture details well below the resolution limit of the detector – opening the door to exciting imaging possibilities, for example, in lung imaging. The standard Grating Based X-ray Phase Contrast Imaging (GBXPCI) technique uses three gratings G0, G1, G2. The first grating G0 provides the partial coherence needed for X-ray interference; the second grating G1 provides the interference of waves that generates a spatially modulated set of fringes at some distance away; the final grating G2 provides the means to interrogate the fringes before the detector. We will review the basic theory, implementation challenges, and some recent developments in literature.
Bio: Dr. Max Yuen received his BS '01 in Applied Physics from Caltech, and PhD '14 in Applied Physics from Stanford University. He was involved in the X-ray phase contrast experimental effort in the Hesselink Group in support of the DHS and TSA program for novel imaging techniques for baggage scanners. Prior to the X-ray project, he has worked on fluorescence enhancement in nano-apertures and its application in fluorescence correlation spectroscopy. During his time at Stanford, Dr. Yuen has also lectured for a number of classes in AP and EE and advised undergrads for the REU program.