New x-ray technique images cartilage, may lead to earlier diagnosis of osteoarthritis

March 17, 2002

An innovative x-ray technique called diffraction enhanced imaging (DEI), which produces images with about 27 times greater contrast than regular x-ray images, could be an extremely valuable tool to physicians trying to detect osteoarthritis, a degenerative disease of the cartilage, while the condition is in its early stages of development. Images taken using DEI, clearly show cartilage, whereas with conventional x-rays, the cartilage is invisible.

Using DEI, the researchers, led by Dean Chapman, associate professor of physics at Illinois Institute of Technology (IIT), and Klaus Kuettner, Chairman of the Department of Biochemistry at Rush Medical College of Rush-Presbyterian Saint Luke's Medical Center in Chicago, have been able to not only image cartilage, but to correlate certain features in their DEI x-ray images with various disease stages of osteoarthritis, a degenerative cartilage joint disease that affects more than half the nation's elderly. The research was published in the March issue of Osteoarthritis & Cartilage.

"Since cartilage is a tissue that cannot be imaged by conventional radiography, this could be an important new tool for diagnosing osteoarthritis much earlier in the disease cycle," says Chapman . Today, conventional x-ray diagnosis of osteoarthritis shows only that bones are getting closer and closer together as the cartilage deteriorates. Chapman and Kuettner believe that DEI can fill the x-ray imaging void in detecting cartilage degeneration earlier.

The DEI images taken used synchrotron radiation from the National Synchotron Light Source at Brookhaven National Laboratory in New York. Sychotron radiation is also produced by the Advanced Photon Source (APS) at Argonne National Labs in Illinois. The APS produces high energy x-rays of a single energy, or wavelength instead of the broader-energy beams of conventional x-ray machines. The x-rays are accelerated through a gigantic ring using magnets before they can be "tapped" for experiments. By placing a crystal in the path of the x-ray beam after it passes through an object, most of the scatter that degrades conventional x-rays is eliminated, resulting in sharper images that highlight the edges of objects and make them stand out against complex backgrounds. And, DEI delivers the same dose of radiation that conventional x-rays deliver, perhaps even less.

DEI works especially well for cartilage because it exists in very discrete shapes with clearly defined edges that DEI excels in picking up. Chapman and colleagues are now looking into developing DEI to screen for osteoarthritis in patients. Moving DEI into a clinical setting is definitely a challenge, says Chapman, but one that can be overcome. Currently, Chapman and his students are looking at alternative energy sources that mimic synchrotron radiation. "Fortunately, DEI isn't reliant on the high energy of synchotron radiation, but on the alignment of the rays" says Chapman. A prototype he is building of a small DEI machine at IIT uses a regular x-ray tube which has produced high-resolution DEI images comparable to those taken at Argonne. A clinical machine is still years away, but Chapman is confident that one day DEI will be available in hospitals and clinics.

Carol Muehleman, of Rush Presbyterian St. Luke's Medical Center in Chicago and one of the leading scientists working with Chapman on the research, is convinced that the new DEI technology has the potential to become an extremely valuable tool to physicians trying to detect osteoarthritis while the condition is in its early stages of development.

"Right now we can only determine, by regular x-rays, if a person is losing their cartilage through degeneration by watching the spaces between their bones get smaller as the cartilage wears down," Muehleman says. "With DEI, we would actually be able to see the cartilage and detect osteoarthritis much earlier for treatment."

The team of scientists at both institutions predicts that pharmaceutical companies developing drugs to treat osteoarthritis may be interested in using DEI. Now, companies induce osteoarthritis in animals either chemically or mechanically before treating them with experimental drugs. To see if the drugs work, the animals' cartilage is observed post-mortem. Now that cartilage can be imaged using DEI, pharmaceutical companies may eventually be able test the efficacy of their drugs throughout the course of the disease process.

The Rush scientists were eager to work with Chapman on imaging cartilage using DEI after seeing DEI images for mammography taken in 1997. The images were of a standard test object used to grade the sensitivity of mammography machines. The object contains tumor-like tissue as well as artificial fibrils found in certain breast cancers. When compared to conventional images of the test object, the DEI images showed almost every single feature in the test object, including the tape that held it in place, while the conventional x-ray image showed only the largest features. The results of the research were published in the March 2000 issue of Radiology. Chapman estimates that DEI images have about 27 times greater contrast than regular x-ray images.

"Because of the high resolution DEI gives, it can also actually show where the cartilage is breaking down, giving us a picture of how the disease progresses in a patient, something we haven't been able to see with x-rays before," Kuettner says.

DEI also has applications in national security. In January, 2002, Chapman used DEI to image a conventional cafeteria knife, which showed up much more clearly than if the knife were imaged using the standard equipment used to scan baggage at airports. It is just one of the ways engineers and scientists at IIT are turning the focus and expertise towards fighting terrorism post September 11.
-end-


Illinois Institute of Technology

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