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An exciting newX-ray imaging technology has been successfully developed to the pointwhere it is nowready for translation into all kinds of beneficial applications, including potentially life-saving uses in security and healthcare. A five-year project led by UCL (University

College London) has developed a breakthroughwhereby, comparedwith conventional X-rays, tumours can be identified in living tissue earlier and smaller cracks and defects inmaterials can be identified. This is because it excels at determining different shapes and different types ofmatter – a capability that conventional X-rays could onlymatch by using prohibitively high doses of radiation. The technique at the heart of the advance

is called phase-contrast X-ray imaging. Instead ofmeasuring the extent towhich tissue ormaterials absorb radiation – as in conventional X-ray imaging – itmeasures the physical effect that passing through different types of tissue ormaterial has on the speed of the X-ray itself. Project leader professor Alessandro Olivo

says: “The technique has been around for decades but it has been limited to large- scale synchrotron facilities, such as Oxfordshire’s Diamond Light Source.We’ve nowadvanced this embryonic technology to make it viable for day-to-day use in medicine, security applications, industrial

Phase-contrast X-ray imaging (PCI) or phase-sensitive X-ray imaging is a general termfor different techniques that use information concerning changes in the phase of an X-ray beamthat passes through an object in order to create its images. Standard X-ray imaging techniques, like

radiography or computed tomography (CT), rely on a decrease of the X-ray beam’s intensity (attenuation)when traversing the sample,which can bemeasured directly with the assistance of an X-ray detector. In PCI however, the beam’s phase shift caused by the sample is notmeasured directly, but is transformed into variations in intensity,which then can be recorded by the detector.

8 /// Environmental Engineering /// February 2017

 Siemens is one of the companies investigating entirely new concepts for X-ray systems. The aim is to achieve a radical increase in imaging resolution and to enable phase-contrast X-ray imaging. This entirely new technique helps, for instance, in the identification of tumours. Moreover, examinations involving cardiovascular diseases can be carried out without contrast agents. Nearly one out of 10 patients suffer from allergic reactions to these substances. A multi-year R&D project, which is scheduled to run until 2017, brings together experts from Siemens Healthcare, Corporate Technology and other partners.

production lines,materials science, non- destructive testing, the archaeology and heritage sector, and awhole range of other fields.” This vast potential is already beginning to

be explored. For example:  Under licence, NikonMetrology UK has incorporated the technology into a

WHAT IS PHASE-CONTRAST X-RAY IMAGING? In addition to producing projection

images, PCI, like conventional transmission, can be combined with tomographic techniques to obtain the 3D distribution of the real part of the refractive index of the sample. When applied to samples that consist of

atoms with low atomic number Z, PCI is more sensitive to density variations in the sample than conventional transmission- based X-ray imaging. This leads to images with improved soft tissue contrast. In recent years, a variety of phase-

contrast X-ray imaging techniques has been developed, all of which are based on the observation of interference patterns between diffracted and undiffracted waves.

prototype security scanner. This is being tested and further developed to provide enhanced threat detection againstweapons and explosives concealed, for example, in baggage.  Building on EPSRC-fundedwork, a new three-year project supported by the Wellcome Trustwill see the Nikon Metrology/UCL teamdevelop a prototype scanner for use during breast cancer surgery in collaborationwith Barts Heath and QueenMary University of London. The aimis to help surgeons determine the exact extent of themalignancy and to reduce the need to recall patients for further operations, resulting inmore effective breast conservation surgery, less need for fullmastectomies andmore rapid treatment.  The technology can even detect some tissue types invisible to conventional X-ray machines, such as cartilage, and plans are proceeding to set up a spinout company to take this aspect towards commercialisation. “This has the potential to be an incredibly

versatile, game-changing technology,” says Olivo. “We’re currently negotiatingwith a number of companies to explore howit could be put to practical use.”

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