Active-MRI, a technique developed at the University of California Davis (UC Davis) School of Medicine, has demonstrated the ability to image wrists in motion, making it possible to investigate dynamic wrist instability in vivo.
Unlike a standard MRI exam, which can take more than 30 minutes total and requires at least three minutes per image set, the active-MRI protocol takes one image every half second and can deliver a series of images in 30 seconds.
"These fast images are like a live-action movie," Robert Boutin, MD, professor of radiology at UC Davis and lead author of the study, said in a press release. "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."
The outcome of initial tests of the protocol was published Dec. 31 in PLoS ONE.
While conventional MRI isn’t fast enough to make a video of a moving wrist, CT and fluoroscopy provide their own challenges in that they involve radiation and don’t show soft tissue ligaments as well as MRI. Boutin and colleagues hoped that active MRI could provide a radiation-free modality to image wrist architecture.
The initial study to test the technique involved images of 15 wrists from 10 asymptomatic volunteers. To help eliminate banding artifacts caused by bone movement, the researchers created a harness with dielectric pads to stabilize the magnetic field and shift artifacts away from the area of interest.
During the 10 minute exam, study volunteers were asked to perform motions such as rotating their wrist or clenching their fist. Boutin and colleagues were successfully able to evaluate distal radioulnar joint subluxation ratios, scaphalunate intervals and abnormalities in extensor carpi ulnaris tendon translation.
The next step for the authors will be to validate the technology in a group of patients with signs of wrist instability, as well as use the technique to study sex distinctions in conditions such as osteoarthritis and carpal tunnel syndrome.
Click below for a video demonstration of an active-MRI showing radial and ulnar deviation of the wrist: