Improving medical students

The Future of X-Ray – Dark Field X-Rays

Posted by medliorator on January 25, 2008

A set of simple silicon filters could dramatically improve the quality of X-ray images produced in hospitals and at airport checkpoints.


X-ray images normally reveal the way different materials, including body tissue, absorb X-ray radiation. finer details are often lost in a fog caused by areas with intermediate radiation-absorbing ability.


researchers led by Franz Pfeiffer of the Paul Scherrer Institute, in Villigen, Switzerland, and including colleagues at the Niels Bohr Institute in Copenhagen, Denmark, have figured out a way to produce much clearer snapshots for little extra cost. The team adapted a technique known as dark-field microscopy, which is normally used by biologists to get a clearer view of cells under a light microscope.


Dark-field microscopy improves the contrast of an image by using only scattered light. Pfeiffer and colleagues have shown that the same principle can be applied to X-ray images. This is done by ignoring conventional X-rays passing through an object and only collecting those that scatter off it instead. The team has developed a set of silicon filters that make this possible: radiation that passes straight through an object can be ignored, and rays bent through a tiny angle, as a result of scattering, are collected.


The process involves taking four separate images, each with the three filters in a slightly different arrangement. Software then compares each snapshot to produce a final high-contrast picture. Although the process means exposing the subject to a higher total dose of radiation, Pfeiffer says this can be justified in some circumstances.


The resulting images reveal physical details that would normally be invisible. For example, since soft tissue and bone differ strongly in their ability to scatter X-ray, the dark-field technique could help a doctor spot small splinters of bone or cartilage after a bad fracture.


The technique is not yet ready for deployment in hospitals as it only works with relatively low-intensity X-rays. However it could be used for some clinical investigations like mammography and Pfeiffer’s team is working on making it suitable for more powerful X-ray machines. They plan to test it on live animals within the next 12 months.

‘Dark field’ X-rays reveal bodies in new detail [NewScientist]


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