Dr. Dean Chapman
Canada Research Chair in X-ray Imaging
We’ve all heard of extreme sports; well, this is extreme x-ray imaging.
Diffraction enhanced x-ray imaging (DEI) is a new technology that makes use of x-ray refraction and scattering as well as absorption in developing image contrast. The new sources of contrast are particularly well suited for soft tissue imaging, which is not easily viewed using conventional x-ray.
“In imaging, everything is contrast,” explains Dean Chapman. “Contrast from conventional radiation comes from absorption—you see features because those features absorb more of the x-rays than the surrounding features. Your lungs, for example, show up on an x-ray because they don’t show up. The kind of imaging we have developed gives you contrast to see soft tissue features.”
When you send an x-ray through the human body it will go through in a nearly straight line—some of the x-rays will be absorbed while others will be bent slightly on their way through. Chapman explains that we can pick up on these very subtle changes of direction caused by density variations.
“With traditional radiography, you try to stop some of the x-rays in the tissue—if you don’t stop anything you don’t get contrast,” he says. “We would like to NOT stop the x-rays at all. Instead, we would like to observe the optical effects as they pass through you—we want to see them being bent at angles; we want to see them being scattered.”
Using the DEI method, an x-ray will interact with the tissue it encounters and then, ideally, come out on the other side. When it comes out, it will contain information about what it “saw” along the way.
“I am developing an instrument that can ask that x-ray what it saw,” Chapman explains. “With conventional radiography, we really aren’t interrogating the beam at the level we aught to be.”
He says, if we try to pick up as many of the interactions as possible, we may be able to interpret the information in a way that will allow us to identify specific tissue types in an imaging system. “Rather than just getting a greyscale image that only shows you density, you could have an image that shows you where cartilage is, for example, or bone, or cancer.”
Not only does DEI produce image quality that is up to 25 times higher than conventional x-rays, it is much less dangerous because 30 or 40 times fewer x-rays are absorbed by the body. The trick is to transfer that technology from a synchrotron. (A synchrotron produces extremely bright light which allows scientists to see the microscopic nature of matter down to the level of the atom.)
“It is one thing to use this technology for research at a synchrotron, but there is not going to be a synchrotron at every clinic,” admits Chapman. “We are trying to determine if we can do this using conventional sources of x-ray.”
The DEI method was developed by Chapman, along with Bill Tomlinson, Director, University of Saskatchewan-owned Canadian Light Source synchrotron, and a graduate student, as part of a synchrotron mammography research program. Another area of active research is finding other applications for the technology. One of the areas they are currently exploring is cartilage imaging, which could potentially aid in the development of drugs to treat osteoarthritis.