Magnetic resonance imaging (MRI)
MRI is an advanced imaging technique that enables us to look very closely at specific areas of a horse, usually the feet or lower legs. This is the same type of technology used in human hospitals, adapted for use in horses.
The Leahurst Equine Hospital has a Hallmarq standing MRI unit. We were one of the first equine hospitals in the UK to install and operate this system and have done scans on over 1,000 horses since then.
When is MRI used?
MRI is useful for assessing the ligaments and tendons in a horse’s lower legs and feet in more detail. It is also very useful for identifying bone bruising and disease. This form of imaging is often undertaken when lameness has been localised to a specific region of the lower leg and has undergone X-rays.
MRI is also used in horses with foot penetrating injuries. For example, if nails or other objects have punctured the foot. This provides us with the best information about the structures that have been damaged and if further treatment such as surgery is needed (e.g. life-threatening infection in one of the synovial structures in the foot).
MRI is a valuable tool in specific cases to help us to make a final diagnosis, guide treatment and make a prognosis about a horse’s athletic future.
How does MRI scanning work?
MRI is a complex imaging technique where strong magnets are used to align the protons in the tissues of the horse's legs. Radio waves are then beamed at the leg, causing the protons to shift out of alignment. When the radio wave beam is turned off, the protons realign, emitting radio waves of their own. The MRI sensors detect these tiny radio waves and turn them into the images we read. All of this is completely painless and non-invasive for the horse.
What does MRI scanning involve?
Horses need to have any metal shoes and associated nails removed as metal interferes with the magnet. Horses are then sedated and are then positioned in the scanner. Each region takes about 45 minutes while approximately 300 images are obtained. Horses are required to stand still to obtain high quality images so fidgety horses can take longer to scan.
These scans are then assessed in depth by our team of specialists, a process that can take several days to do properly. Once the diagnosis is made, treatment options are discussed with the owner of the horse and their usual veterinary surgeon.
What type of conditions can be diagnosed?
Common injuries detected on MRI of the horse's foot include arthritis of the coffin joints, injuries to the deep digital flexor tendon, navicular disease and collateral ligament injury. Many lame horses have more than one injury per foot and sometimes further nerve blocks and additional tests are required to work out which is the more significant injury.