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Magnetic Resonance Imaging (MRI):

MRI 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 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 required 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 (or the hind shoes if the hind legs are being scanned) need to be removed prior to the scan. The entire scanning procedure takes between 2 and 4 hours, depending on the area being scanned and the temperament of the horse, however, in some complicated cases, the procedure may take even longer than this. As far as it is known, the procedure is perfectly safe and it does not involve exposure to any form of ionising radiation.

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. However, the area being scanned must be localised (usually by means of nerve blocks) prior to the procedure taking place.

One of the most useful indications for standing MRI is in the evaluation of horses with lameness originating in the foot. Our experience has shown that many horses with chronic foot lameness affecting either one or both front feet, have a variety of concurrent soft tissue injuries. These particular injuries cannot be accurately diagnosed using more conventional techniques. MRI has also proven to be very accurate in diagnosing many bone diseases (including early navicular disease and pedal bone diseases) that are difficult or impossible 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.

MRI Guidance Notes:

  • 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. Wherever possible this should be done well in advance of your appointment date. You can download our guide for insurance claims for day-case appointments HERE.
  • We will provide an estimate for the costs of the MRI examination, but in some cases we will determine that further scanning of more areas of the limb(s) with be required - this may incur extra cost, but we will discuss this with you (and usually your veterinary surgeon) before incurring further costs.
  • Please bring details of your insurance policy (i.e. 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 previous problems that the horse has encountered when being sedated, please inform us prior to arrival.
  • Please bring the horse’s passport with you.
  • Shoes need to be removed before the procedure can be carried out. If your horse is having its forelimbs scanned only its front shoes need to be removed and only hind shoes for scanning hind limbs. If your horse is coming specifically for MRI, then shoes can be removed before the horse arrives at the clinic. However, if your horse is being examined prior to an MRI at Bell Equine, shoes should be left on so we can assess the lameness. 
  • Horses should arrive for the scan with clean, dry feet. Unfortunately any purple or blue spray applied to the feet can seriously affect the image quality. To improve this please stop using the product at least 5 days prior to the scan and make sure that any spray left on your horse is thoroughly cleaned off. 
  • Your horse may have to remain at the clinic for the whole day. Although the initial scanning procedure only takes a few hours, having the horse at the clinic for longer will allow time for repeat scans to be taken if deemed necessary.
  • You will be informed when your horse can leave the clinic, normally as soon as we have completed the scan and checked to see that we have images of diagnostic quality. Arrangements to collect the horse can be made at this time.
  • Due to the large amount of information collected during the procedure, it is unlikely that you will receive any results before your horse is discharged. In most cases a full report will be produced within 3-5 days and copies will be sent to yourself and your referring vet.
  • Routine X-rays will be taken of horses having MRI of the feet prior to the procedure.  This is for our own research and development purposes and there will not be a charge for this.  It also gives us the opportunity to check for any broken clenches or rust that has been left in the feet which will have to be removed as they would adversely affect the image quality.
  • In some cases, the MRI scans will identify a problem where we believe further imaging (such as radiography, ultrasonography or nuclear scintigraphy) 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 a small number of horses, sedation may predispose them to mild colic. If your horse is prone to colic, it might be prudent to feed a laxative diet or add extra table salt to the feed (eg one tablespoon per feed) for 24 hours or so before coming for the MRI and after your horse returns home. In a few cases we may recommend giving the horse an electrolyte solution by stomach tube before travelling home. If feasible, walking exercise can also be helpful to promote gut motility.

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 fared 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 it continues to reveal new conditions that it is discovering all the time. An important way of increasing our knowledge is by correlating the results of MRI and post-mortem examinations. If, for any reason, a horse that has previously had an MRI scan has to be euthanased, then we would welcome the opportunity to perform a post-mortem examination of the scanned area. In this way we can further increase our knowledge and expertise for the benefit of horses in the future.

If you have any further questions or require more information, then please do not hesitate to contact us on 01622 813700 and ask for the hospital team.