In optical microscopy , dark-field imaging is a well-established means of enhancing contrast. By diverting most of the illuminating light before it reaches the focal plane and imaging only with light that scattered within the sample, one can highlight small scattering inhomogeneities that are hard to discern in the glare of the illumination source.
One would like to do the same with x-ray imaging. Bone and some pathological tissues incorporate microscopic x-ray scattering sites that would provide much better contrast than one gets with conventional medical radiographs, which rely entirely on x-ray absorption. Dark-field x-ray imaging would also help security screening by distinguishing between microscopically homogeneous soft materials and similarly absorbing explosives like Semtex that incorporate telltale micro-granule scatterers. And for safety inspection of materials, microfractured regions would reveal themselves as x-ray scatterers in a dark-field image.
The problem with x rays, and especially with the hard, multi-keV x rays...
