X-Ray Images Made Clearer by New Technology

Dark-field images provide more detail than ordinary X-ray radiographs and could be used to diagnose the onset of osteoporosis, breast cancer, or Alzheimer's disease; to identify explosives in hand luggage; or to pinpoint hairline cracks or corrosion in functional structures; according to the researchers who developed the technique, from Paul Scherrer Institute (PSI; Villigen PSI, Switzerland) and the Ecole Polytechnique Federale de Lausanne (EPFL; Switzerland).

Up to now, dark-field X-ray imaging required sophisticated optics and could only be produced at facilities such the PSI's 300 m-diameter, US$200 million synchrotron. With the new nanostructured gratings described in this research, published online January 20, 2008, in the journal Nature Materials, dark-field images could soon be produced using ordinary X-ray equipment already in place in hospitals and airports around the world.

Unlike conventional X-ray images, which show a simple absorption contrast, dark-field images capture the scattering of the radiation within the material itself, exposing slight inner changes in bone, soft tissue, or alloys. The overall clarity of the images is striking. The improved sensitivity in measuring bone density and hairline fractures could help diagnose the onset of osteoporosis. Because cancer or plaque cells scatter radiation slightly differently than normal cells, dark-field X-ray images can also be used to examine soft tissue, providing safer early diagnosis of breast cancer or the plaques associated with Alzheimer's disease.

Security screening equipment equipped with dark-field image capability could better identify explosives, whose microcrystalline structures strongly scatter X-ray radiation. In addition, because X-rays penetrate a material without damaging it, dark-field images could help reveal scattering-producing micro-cracks and corrosion in structures such as airplane wings or the hulls of boats.

"Researchers have been working on dark-field X-ray images for many years,” explained Dr. Franz Pfeiffer, a professor at EPFL and researcher at the PSI. "Up until now these images have only been possible using sophisticated crystal optical elements.” Crystal optics, however, only work for a single X-ray wavelength, and therefore, are highly inefficient. "Our new technique uses novel X-ray optical components, in the form of nanostructured gratings, that permit the use of a broad energy spectrum, including the standard range of energies in traditional X-ray equipment used in hospitals or airports, added Dr. Christian David, Dr. Pfeiffer's colleague at PSI. "This opens up the possibility for adapting current imaging equipment to include dark-field imaging.”

Dr. Pfeiffer plans to collaborate with the Center for Biomedical Imaging (CIBM; Geneva, Switzerland), a joint center with the Universities of Lausanne and Geneva (Switzerland) and their associated hospitals, to develop an adaptation for existing medical equipment. "When combined with the phase contrast imaging technique that we developed in 2006, we now have the possibility of providing the same range of imaging techniques in broad-spectrum X-ray imaging that we do with visible light.”


Related Links:
Paul Scherrer Institute
Ecole Polytechnique Federale de Lausanne