“I am here to convince you that MRI (magnetic resonance imaging) is in all your futures, so you are going to have to develop some familiarity with this,” began Robert Schneider, DVM, MS, equine orthopedic surgeon at Washington State University, during his presentation on this imaging modality at the 2005 American Association of Equine Practitioners Convention, held Dec. 3-7 in Seattle, Wash. “It’s been a valuable diagnostic tool at Washington State since 1997. MRI is changing the treatment of horses with lameness problems in the distal limb.”

He explained that MRI is a hydrogen proton-based technology that generates images based on the biochemistry of the limb, not architecture (as does ultrasound). It provides detailed images of bone and soft tissue structures, highlighting different structures depending on the type of MRI image used. (Some highlight fluid, while others are best for showing anatomical structures.) At Washington State, horses are put under general anesthesia for MRI imaging and usually spend less than 90 minutes in the machine.

“MRI is indicated when a lameness diagnosis can’t be made from radiographs, ultrasound, or scintigraphy, and we know the location is in the distal limb,” Schneider said. “You must have the lameness pretty well localized; this is critical.” In other words, one doesn’t screen the whole limb with MRI looking for a problem. Rather, you focus on a specific problem area.
“Slice planes can be oriented in any direction through the leg,” he said. “Orienting slice planes through specific anatomic structures has increased our ability to see some pathologic abnormalities.

“Clients will soon be bringing you horses with MRI images that you’ll have to interpret,” Schneider said. “It’s like a cool computer game to look at these images of horses with lameness problems. We try to send CDs to all the referring veterinarians so they can develop some familiarity with looking at these things. Sometimes it’s like looking at the ocean with all the abnormalities you can find