Moving images could be invaluable when it comes to diagnosing wrist problems say a group of researchers at University of California-Davis. The multi-disciplinary team of radiologists, medical physicists, and orthopaedic surgeons say that they have found a way to create “movies” of the wrist in motion using a series of brief magnetic resonance imaging (MRI) scans. Called “Active-MRI,” the technique could be used to diagnose subtle changes in physiology that indicate the onset of conditions such as wrist instability.

Fig. 1 – The forearm of a healthy volunteer in the wrist harness.

“These fast images are like a liveaction movie,” said Robert Boutin, professor of radiology at UC Davis and lead author of the study. “The movie can be slowed, stopped, or even reversed as needed. Now patients can reproduce the motion that’s bothering them while they’re inside the scanner, and physicians can assess how the wrist is actually working. After all, some patients only have pain or other symptoms with movement.”

Wrist instability can occur when carpal bones become misaligned and affect joint function. This often occurs as a result of trauma to the ligaments between wrist bones. It causes abnormal mobility and chronic pain that can lead to osteoarthritis. Early diagnosis, when less-invasive treatments are possible, can lead to good outcomes in managing the condition.

Current methods, such as dynamic computed tomography and fluoroscopy, can image a moving wrist, but these approaches involve radiation and do not show soft tissue as well as MRI scans.

“MRI scans provide detailed anatomical information of wrist structures without using ionizing radiation, but they cannot help diagnose problems with bone or tendon position that are best seen when the wrist is moving,” said Abhijit Chaudhari, assistant professor of radiology at UC Davis. “Active-MRI provides a detailed and ‘real time’ view of the kinesiology of the wrist in action using a widely available and safe technology.”

However, adapting MRI capabilities to providing moving images required overcoming a number of serious hurdles. A complete MRI exam usually takes at least 30, with each image set requiring at least three minutes—not nearly fast enough to make a video. So, the team developed a new protocol that takes one image every 0.5 seconds, delivering a series of images in a half minute.

Another barrier was the presence of imaging errors called banding artifacts. Movement of the bones in the wrist area can interfere with the scanner’s magnetic field, creating signal drop-offs. The resulting dark bands can obscure the moving wrist. The team overcame this problem with dielectric pads, which stabilize the magnetic field and shift artifacts away from the area of interest and to the side, allowing doctors to clearly see the wrist bones.

Active-MRI was tested on 15 wrists of 10 subjects with no symptoms of wrist problems. The participants’ wrists were imaged as they performed motions such as clenching the fist, rotating the wrist, and waving the hand side-to-side. Each exam lasted ten minutes.

Their next step is to validate the technology by using it on patients with symptoms of wrist instability. In addition, they plan to use Active-MRI to study sex distinctions in musculoskeletal conditions, including why women tend to be more susceptible to hand osteoarthritis and carpal tunnel syndrome.

NASA Tech Briefs Magazine

This article first appeared in the February, 2014 issue of NASA Tech Briefs Magazine.

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