By exploiting the spatial coherence of X-ray beams coming from synchrotron light sources one can study several phenomena having a possible impact on diagnostic radiology. Conventional absorption radiology is based on the different X-ray absorption properties of different materials. A severe limitation of this method is the fact that low density biological samples having low X-ray absorption produce low values of the image contrast and a scarce visibility of the details. This is typically the case of mammography, where one wishes to examine soft tissue. An alternative approach to absorption is the so-called "phase contrast radiology" where, besides absorption differences, one detects the phase shifts undergone by the electromagnetic wave after traversing a given detail.
  This is equivalent to saying that image contrast is produced using the real part of the refractive index, which determines phase shift properties, rather than its imaginary part, which determines absorption properties: hence the name "phase contrast imaging". The picture shows the comparison between a conventional absorption radiography of a mimosa flower (A) and a phase contrast image of the same object (B).