By introducing an analyzer crystal between sample and detector it is possible to convert into images the information on the sample carried by the phase of the wave which traversed it.
  When aligned with the monochromator crystal placed upstream of the sample, the analyzer crystal rejects all scattered photons, which blur the image and reduce detail visibility.
  A slight misalignment angle between the two crystals transforms into different shades of gray on the detector film the different scattering angles of the photons which traversed the sample. These angles are, to first order approximation, proportional to the gradient of the real part of the refractive index, which is responsible for wave phase shifts. In this way one can convert into image contrast the information on the sample internal structure carried by the phase of the wave.
 The picture shows an image of a bee (which is practically transparent to X-rays used in dagnostic practice) obtained with this technique.