X-ray Dark Field Imaging

摘要

A new kind of enhanced contrast X-ray imaging of weakly absorbing materials in dark field mode is presented. Samples such as plastics and biological tissue are a perpetual challenge for radiographic imaging. Recent innovative approaches such as Diffraction Enhanced Imaging (DEI), "phase contrast", grating interferometry (Talbot-Lau), or Refraction Enhanced Imaging (REI) have in common that they yield enhanced contrast based on deflected X-rays. Here, we introduce a REI modification, which works with a slightly bent single crystal reflecting in Bragg geometry. The samples are placed upstream of the thin crystal within a parallel synchrotron beam. The crystal's curvature creates a dark-field stripe in the transmission image, similar to the inverse of a Darwin-Prins rocking curve of plane crystals. The reflection condition is met better or worse as a steady function of incidence position. Refracted beam portions of sample interfaces appear bright on black stripes. The entire image is finally synthe-sized by multiple dark-field stripes. The technique is an alternative to the mentioned techniques. We demonstrate the technique's advantage by examples of biological and technical microstructures.