MR Image Orientation (Images are displayed like “slices” through the leg. The orientation terms refer to the direction of the slice.)
Sagittal (SAG): Vertical slices, from left to right across the leg.
Transverse (TRA) or Axial: Horizontal slices across the leg, top to bottom and front to back and rotated to align with the anatomy of the part being imaged.
Frontal (FRO), Dorsal or Coronal (COR): Vertical slices from front to back. These images are also rotated to align with anatomical structures.
Sagittal
Transverse (Axial)
how well the horse stands in the magnet determines how clear the images are. Feet are by far the easiest as there is little movement from the patient during the scanning process. It’s one thing to put a horse under anesthesia for colic sur-
gery to save his or her life—that is worth the risk of complica- tions, but it’s another thing to unnecessarily risk your horse’s life for an elective, diagnostic procedure. The low field, standing magnet only requires a horse to be sedated enough to stand quietly. They remain awake during the procedure and intravenous sedation is given through a catheter before and during the procedure, according to the horse’s response. Besides being safer for the horse, it’s more affordable for the owners. Overall, the benefits of a low field system far out- weigh the disadvantages of a high field system in lower limb diagnostics.
When Is MRI Right for Your Horse? In the performance horse, a common outcome of a lameness
work-up is a horse that goes sound when blocked to a region on the limb but often has no visible changes on radiographs or ultrasound. In these cases, veterinarians have no choice but to assume a particular diagnosis and rely on the response
78 January/February 2014
Frontal ( Dorsal)
to treatment in order to determine if their assumption is ac- curate or not. Using a standing MRI helps to eliminate these “educated guesses.” Until the development of the MRI, many lameness cases
have been inaccurately diagnosed, especially in the foot. (See sidebar regarding a foot pain study.) Besides providing diag- notics images in areas that other modalities cannot access, the MRI is the only technique that distinguishes between the many causes of palmar (heel) foot pain. As a result, this tool allows veterinarians to evaluate both bone and soft tissue in the foot to determine if there is an acute injury or a chronic problem. The MR images created provide an abundance of information on the area in focus, giving veterinarians and owners a collective picture of what’s going on. Bone, tendons, ligaments and other soft tissues are all displayed together. More and more equine veterinary clinics are embracing
this tool and are delivering more targeted diagnoses, better treatments and thus better results for the horses. It’s another way our industry is advancing to improve the health and wellness of our equine athletes.
To see a complete list of where the standing MRI units have been installed, go online to
www.hallmarq.net.
Illustrations by Amy Stuverude
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