In Search of an Earlier Diagnosis of Osteoarthritis

Originally Published MDDI April 2002

R&D DIGEST

Because radiography is incapable of imaging cartilage, conventional x-ray diagnosis of osteoarthritis can only demonstrate that bones are getting closer and closer together as that tissue deteriorates. Now, a technique called diffraction enhanced imaging (DEI) may provide an important tool for diagnosing osteoarthritis by detecting cartilage degeneration at an earlier stage in the disease.

Led by Dean Chapman, PhD, associate professor of physics at Illinois Institute of Technology (IIT; Chicago), and Klaus Kuettner, PhD, chair of the Department of Biochemistry at Rush Medical College of Rush-Presbyterian Saint Luke's Medical Center (Chicago), the research team has used DEI to image cartilage, and correlate certain features in the images with various disease stages of osteoarthritis. The researchers explain that DEI delivers the same dose of radiation that conventional x-rays deliver, perhaps even less.

The research team used synchrotron radiation from the National Synchrotron Light Source at Brookhaven National Laboratory (New York) to generate the DEI images. Synchrotron radiation is also produced by the Advanced Photon Source (APS) at Argonne National Labs in Illinois. The researchers explain that APS produces high-energy x-rays of a single wavelength, instead of the broader-energy beams of conventional systems. Accelerated through a large ring using magnets, the x-ray beam is "tapped" for experiments. Placing a crystal in the beam's path after it passes through an object eliminates most of the scatter that degrades conventional x-rays. This results in sharper images that highlight the edges of objects and provide greater contrast with complex backgrounds.

The scientists speculate that DEI is well suited for cartilage because the tissue exists in discrete shapes with clearly defined edges that DEI can clearly capture. The IIT researchers are now looking into developing DEI to screen for osteoarthritis in patients. Chapman considers moving DEI into a clinical setting to be a challenge. The group is currently considering alternative energy sources that can mimic synchrotron radiation. Says Chapman, "Fortunately, DEI isn't reliant on the high energy of synchrotron radiation, but on the alignment of the rays." He explains that a small prototype DEI machine at IIT uses a regular x-ray tube. The unit, however, has produced high-resolution DEI images comparable to those taken at Argonne.

Carol Muehleman, PhD, of Rush Presbyterian and one of Chapman's collaborators, believes that DEI has the potential to become a valuable diagnostic tool for physicians. "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," she says. "With DEI, we would actually be able to see the cartilage and detect osteoarthritis much earlier for treatment."

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