MAGNETIC resonance imaging (MRI) was first performed on live horses at Washington State University in 1997. Over the last 20 years, this diagnostic modality has been intensively developed and improved considerably. Corresponding with the development of the standing MRI scanner, there has been a steep increase in clinical use during the past 10 years. Troytown Grey Abbey Equine Hospital and Hallmarq Veterinary Imaging co-operated to install the only equine MRI unit in Ireland.

Standing equine MRI can image structures along the entire lower limb, from the foot to the knee or hock. Images are taken as slices through the limb, at an angle and position determined by the system operator according to the results of prior tests (such as nerve blocks and X-rays). By positioning images either parallel or at right angles to key structures, any clinical abnormalities such as inflammation, enlargement or degeneration are clearly revealed in a way that has no parallel in X-ray, CT, ultrasound or nuclear scintigraphy (bone scanning).

Standing MRI has the ability to accurately identifying the specific cause of lameness in over 90% of cases, according to Warren Schofield. Soft tissues are barely visible on X-ray, and bone changes which show up clearly on MRI may never appear or may appear weeks later using X-rays. MRI most often results in an immediate and definitive diagnosis even in hard-to-image areas such as within the foot. Schofield stated that: “The success rate of diagnosis with MRI highlights the limitations of X-ray. X-ray identifies the specific cause of lameness in maybe less than 50% of cases”.

MRI shows ligaments, tendons and bone in great detail. Schofield explained that: “Often bone problems are ruled out because X-rays are normal. However, bone bruising is very common and can cause lameness in many horses, especially jumpers or those working at high-speed. An MRI scan can give owners a definitive answer and it means that the horse will be treated appropriately - often all that is necessary to help the bone heal is rest.”

“The aim of the MRI facility is to speed up the diagnosis process and help racehorses, sport horses and leisure horses back on the road to recovery. All kinds of horse owners are making use of the facility, with an early and accurate diagnosis, treatment can be more specifically targeted to the known cause of lameness. This will hopefully reduce recovery time and any risk of further injury.”

Schofield continued by saying: “Undoubtedly we, as veterinarians, are working more in conjunction with farriers and physiotherapists to help treat lameness.”

Often during a lameness work-up nerve blocks will be used to discover where the pain is coming from. This is then followed by X-ray or ultrasound examinations, but because these imaging tools only show bone (X-ray) or mainly soft tissues (ultrasound) it is common not be able to identify the significant problem.

In these cases a standing MRI can save time, money and worry through an early, safe and accurate diagnosis.

You don’t have to spend money trying different treatments before resorting to MRI months later. MRI scans are safe because it is performed in standing horses, thus avoiding the risks of general anaesthesia in our elite athletes, and accurate because, in the absence of X-ray or ultrasound findings, you often have to rely on judgement and not a positive, clear diagnosis.

MRI CASES

MRI needs to be used in conjunction with a thorough clinical examination and other appropriate tests. The following criteria will help to select the correct cases:

  • Chronic lameness which has been localised to the foot or in the lower limb by nerve block.
  • In situations where X-rays are negative or equivocal.
  • Access to the injured area by ultrasound is difficult or impossible.
  • For penetrating foot injuries needing urgent attention.
  • After acute onset of lameness during exercise.
  • To monitor treatment and healing before returning to work.

    • THE PROCESS

    The Hallmarq MRI Scanner is located in a purpose designed building, situated within the main equine hospital site. A specialist team of veterinarians and nurses at Troytown Grey Abbey are fully trained to use the scanner.

    It takes a few hours to get quality MRI scans and the horse will have to be sedated for the scanning so that they stand very still. The scans can be organised on an out-patient basis, or by admittance to the hospital for the period necessary to get the scans.

  • The shoes are removed and, for foot scans, checks made for residual nail fragments.
  • The horse is sedated and stood in an electrically screened room with its leg inside a large magnet.
  • Scanning takes 1-2 hours for each area scanned, possibly longer if a horse is uncooperative. Then the horse will need some time to recover from sedation before going home.
  • Typically 500-600 images are collected, and interpreted by a specialist which may take 24-72

    • hours.

  • No ionising radiation is used and there are no known biological effects of magnetic fields.

    • If you would like further information on MRI scanning, contact Troytown Grey Abbey on 045 521686.