Medical X rays are so penetrating that they pass right through the soft tissues that can reveal diseases the bone does not. But a novel X-ray imager, developed by anatomist Carol Muehleman of Rush Medical College in Chicago, physicist Zhong Zhong of Brookhaven National Laboratory, and numerous colleagues, brings tendons and ligaments, even skin and blood vessels, into view.
The new method, called diffraction-enhanced imaging, takes advantage of the intense X-ray beam generated at the National Synchrotron Light Source, a particle accelerator at Brookhaven. Once filtered and collimated, the beam passes through the body part being studied and onto a silicon crystal, which bounces the X rays onto film. Each type of soft tissue bends the X rays by a slightly different amount, which influences the intensity of the rays reaching the film. The final image offers an exceptionally clear view of the boundaries between tissues, allowing it to show, for instance, the way the surface of cartilage turns rough in the early stages of osteoarthritis.
Conventional X rays (left) focus on the bone. A new type of image (right) reveals tendons, fat, and skin as well.Photographs courtesy of Zhong zhong/Brookhaven National Laboratory (2).
In tests on cadaver toes, researchers could clearly see skin, nails, tendons, and the fat pad in the ball of the foot. "We are picking up different tissue characteristics than MRI can pick up, and the imaging times are much shorter. We're talking seconds as opposed to sometimes 45 minutes," says Muehleman. The research team is now adapting the technique to smaller, more practical X-ray sources.