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INFORMATION FOR HORSES HAVING MRI |
MRI (magnetic resonance imaging) is a diagnostic imaging technique that involves placing the part of the body to be imaged inside a strong magnetic field. Pulses of radio waves are applied to the area, and a signal (also in the form of radio waves) is received by a computer which generates the image.
MRI is a relatively new technique in equine medicine. At Bell Equine Veterinary Clinic we have a MRI scanner that can be used to image the lower leg area (from foot to knee or hock) of standing horses. Our clinic was the first veterinary clinic in the world to use this technology (the first scanner was installed in 2002, and has since been upgraded). Prior to this, MRI could only be undertaken in horses at a few centres around the world using human MRI scanners. The standing equine MRI scanner has considerable advantages over more conventional human MRI scanners, which require the horse to be placed under general anaesthesia. Our clinic has played a central role in developing this technology for clinical use in horses, and we have acquired unrivalled expertise in this area.
The standing equine MRI scanner is a low field (0.27 Tesla) scanner. Horses are scanned standing under sedation. The front shoes need to be removed (or the hind shoes if the hind legs are being scanned). The entire scanning procedure may take between 1 to 3 hours, depending on the area being scanned and the temperament of the horse. As far as it is known, the procedure is safe and it does not involve exposure to any form of ionising radiation (unlike radiography, CT scanning and nuclear scintigraphy).
MRI allows evaluation of both bone and soft tissues at the same time. The technique has specific indications for the evaluation of certain types of lameness in horses, and the area being scanned must be localised (usually by means of nerve blocks) prior to having the MRI performed. One of the most useful indications for standing MRI is in the evaluation of horses with lameness originating inside the foot. Our experience has shown that many horses with chronic lameness affecting either one or both front feet have a variety of soft tissue injuries (such as damage to the deep digital flexor tendon or one of the many ligaments in the foot); these injuries cannot be accurately diagnosed using more conventional techniques. MRI is also very accurate in diagnosing bone diseases (including early navicular disease and pedal bone diseases) that are difficult to diagnose in any other way. MRI also has many applications in evaluating other diseases in the lower legs, and our knowledge concerning its value is expanding all the time.
GUIDANCE NOTES FOR OWNERS OF HORSES HAVING MRI AT BELL EQUINE VETERINARY CLINIC
• If your horse is insured, you should inform the insurance company that we intend to undertake a MRI examination and, where appropriate, check that the insurers are prepared to cover the costs of this examination. This should be done well in advance of your appointment date.
• Please bring details of your insurance policy (ie company name and policy number) with you.
• Your horse will need to be sedated for the scan. If you know of any reason why this cannot be done safely or if you know of any problems that the horse has previously encountered when being sedated, please inform us prior to arrival
• Please bring the horse’s passport (if available) with you.
• The front shoes (for scanning front legs) or hind shoes (for scanning hind legs) will need to be removed. If your horse is coming specifically for a MRI scan, it will be helpful if the shoes can be removed before the horse arrives at the clinic.
• Wherever possible, the horse should be admitted and remain at the clinic for at least one day. Although the scanning procedure only takes a few hours, having the horse at the clinic for this period allows time for repeat scans to be taken if deemed necessary. The MRI scanner is a highly technical piece of equipment, and as such is prone to faults and unpreventable problems. If the horse remains at the clinic for a whole day, this is usually long enough to allow faults and problems to be resolved before the horse is due to go home.
• Owners will be telephoned as soon as we have performed the scan and checked to see that we have a good set of images. Arrangements to collect the horse can be made at this time.
• The MRI scanning produces a large amount of data and many separate scans. Reading these scans and preparing a report is time consuming, and usually takes at least 2 to 3 hours. In most cases it will not be possible to prepare a full report or to give the owner the results of the scan before the horse has gone home (however, we will ensure that the images are checked to establish that we have enough information to produce an accurate report). In most cases, a report will be produced within 72 hours of the horse going home. All owners and their referring vets will receive a copy of the report.
• In some cases, the MRI scans will identify a problem where we believe further imaging (such as radiography or ultrasonography) will be helpful in providing more information. In such cases, we may request permission to perform these added tests before the horse goes home.
• In view of our interests in researching the applications of MRI to lameness diagnosis in horses, we are always interested in hearing how individual horses have faired after they have returned home from having a MRI scan. We may contact owners in the future to find out how the horse has got on.
• Equine MRI is still in its infancy, and we are learning about many new conditions that it is discovering all the time. An important way of increasing our knowledge is by correlating the results of MRI with post-mortem examinations. If, for any reason, a horse that has had an MRI scan is destroyed, then we would welcome the opportunity to perform a post-mortem examination of the part that was scanned. In this way we can further increase our knowledge and expertise for the benefit of horses in the future.
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