U researchers create 3-D x-ray for hip displacement

By Lana Groves, Asst. News Editor

U researchers have a new device that gives them Superman-like x-ray vision.

Instead of looking through walls, researchers will use two digital x-ray cameras, attached to special types of x-ray machines that enable them to capture motions of bones as they move in real time.

“This is the new x-ray technology of the future,” said Ashley Kapron, a U doctoral student in bioengineering who works with the device. “We’re hoping to start using the equipment on human subjects in the next year.”

The system is unique because it joins data from two standard x-ray imaging devices, fluoroscopes and a CAT scanner, to create 3-dimensional models of the bones that move exactly the way they do in a human subject. A normal CAT scan can provide a 3-D model of the bones, but cannot capture moving images as a patient must hold still to prevent blurring.

“It’s like a miniature x-ray system (that) helps the surgeon determine where he needs to place the device when he can’t see,” said Andrew Anderson, assistant professor and researcher of orthopaedic surgery. “We’ve retrofitted the normal fluoroscopes with high-speed digital cameras.”

The researchers plan to use this device to study abnormalities of the hip, including hip dysplasia. The subjects can walk up and down on a treadmill instead of standing still to allow movement of the skeleton within the field of view of the fluoroscopes.

Kapron said researchers could develop models of individual patients to pinpoint sources of pain and areas where surgical correction may be necessary. With the help of the cameras, the CAT scan will capture the movement of the hip joint and be able to determine where the pressure is coming from.

“That will give us the movement, which we put in the finite element software,” she said.

Researchers are at least a year away from using the device on human subjects. The recently-installed cameras require approval from the Food and Drug Administration.

“We have to prove that the device is just as safe, (if not) safer, than it was when we made the changes,” Kapron said. “We have to test and validate (the device) on cadavers.”

Anderson said radiation technicians will test the device to make sure it doesn’t distribute more radiation than allowed by FDA regulations. He is working with a radiation safety officer at the U to minimize the doses of radiation from the device by acquiring images from subjects only for a few seconds.

When the device is ready, Anderson and Kapron will be able to see where the highest pressure point is on a patient’s hip.

Kapron said hip abnormalities are a problem for athletes and young adults between the ages of 18-23, especially because joint problems are not always fixed through surgery.

“In the long term, it will degrade the cartilage in your joint,” she said. “It can lead to osteoarthritis.”

“We hope that if we’re able to catch it early on, we could reduce the progression at a more acceptable rate,” Kapron said.

Christopher Peters, an orthopaedic surgeon at the U, is one of about 30 surgeons nationwide trained to operate on young adults with hip dysplasia. He plans to use the device to reorient the hip joint to alleviate areas of high stress in hopes of delaying or preventing the need for a total hip replacement. The 3-D imaging device could also be used on a patient before and after surgery to note the success of the hip displacement.

The device is used at other university hospitals and medical centers, but this is one of the first times a high-speed digital camera has been retrofitted to record the image.

Funding for the $150,000 device came from the U Orthopaedic Surgery Center.

Eventually, researchers may be able to use the device to image other physical ailments besides hip displacement or joint problems.

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