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Stanford Report, October 22, 1997

New dimension to joint imaging: 10/22/97

Adding a new dimenstion to joint imaging

Stanford's MRT scanner belongs to a new generation of magnetic resonance imaging systems that are giving radiologists a completely different way to image injured and diseased joints.

Magnetic resonance imaging of joints through their full range of motion requires a system, such as the MRT, that has an open configuration instead of the narrow tube of a conventional scanner. Two Stanford researchers are exploring the MRT's capabilities for dynamic imaging of the knee, shoulder and other joints.

Conventional magnetic resonance imaging typically provides static images obtained with the patient lying motionless in the scanner, explained Dr. Gabrielle Bergman, an assistant professor of radiology and chief of musculoskeletal imaging, who is conducting the joint studies with Dr. Christopher Beaulieu, assistant professor of radiology.

"With the MRT, we can now have the patient stand up and do the movement that causes pain, and see what happens inside the joint when it's in that position," Bergman said. "This is a completely new approach, so it's very exciting."

For knee studies, the MRT's design allows the patient to stand upright in the scanner and bend and stretch the knee during imaging. Images of the weight-bearing knee in motion are very different from standard images of the knee at rest in a neutral position, Bergman said. "You can see problems such as abnormal patellar tracking [misalignment of the kneecap], which may play a role in retropatellar pain syndrome," she said.

A special device called a tracking coil makes these exams possible. Taped onto the patient's skin over the joint being imaged, the tracking coil tells the scanner precisely where the joint is as the patient moves, so the images all show the same part of the anatomy.

The shoulder ­ one of the most complex joints in the body ­ can be examined through its full range of motion in the MRT. The physical examination an orthopedist might perform as a first step in diagnosing shoulder pain can now be repeated with the patient in the scanner, adding a whole new dimension to the exam.

"The doctor can stand right next to the patient during imaging, moving the patient's arm and seeing what's going on internally," Bergman said.

At this point, radiologists are still learning how to interpret the images obtained using these new techniques. Soon, however, the MRT scanner may be used more routinely in the diagnosis of joint problems, Bergman said.