In addition to discerning finer details than current methods, this technique could require a lower overall X-ray dose to produce an image. A conventional X ray relies on differences in the amount of radiation that various tissues absorb. Dense tissues, such as bones, absorb more radiation and cast sharp shadows that show up on a piece of film, while soft tissues block the beam less effectively. A phase-contrast X ray, on the other hand, records information from the beams themselves after they have passed through different tissues.
All tissues cause the X rays to slow down, resulting in what's known as a phase shift.
The size of the shift depends on the type of tissue. In the experimental setup that Wilkins' group used, the X-ray beam had a spot size of 20 micrometers or less, which makes the wave crests well matched, although not as completely correlated as in a laser. Also, the distances between object and image are larger than those used in X-ray imaging, Wilkins says. Those experiments typically require X rays of a single wavelength, so samples must be taken to the nearest high-energy synchrotron.