RVC Equine uses two MRI systems: one low-field system dedicated to scanning distal limbs of the standing horse, and one high-field, human scanner which we share with our small animal colleagues which can perform more detailed scans of the heads of anaesthetised foals.

MRI allows the thorough evaluation of soft tissues, but also bone and is ideally suited for the diagnoses of lesions within the foot, the most common site of lameness.

Our high-field MRI is most commonly used for the evaluation of the brain in foals showing signs of neurological problems. MRI is probably the most difficult modality to perform. Our team has the imaging and clinical experience to guarantee you the best possible care for your horse.

How does it work?

• MRI produces a stack of cross-sectional images based on the magnetic properties of tissues.
• The RVC uses a low-field MRI system for scanning legs in the standing, sedated horse and a high-field scanner for heads and leg scanning under general anaesthesia.
• The horse's leg is positioned in a magnet field with a magnet placed around the area of interest.
• Pathological processes cause the magnetic properties of tissues to change which is then shown on the image.
• During the procedure several images in different contrasts (weightings) and planes are acquired, which can take about an hour per limb and area.

What does it show?

• MRI allows simultaneous examination of both bone and soft tissue structures in three dimensions.
• It can show injuries to tendons and ligaments as well as bones and joints.
• It is especially helpful in the equine foot, the most common site of lameness in the horse.

When do we use it in the horse?

We use standing MRI when we suspect a lesion that does not show up on radiographs or ultrasound, e.g. suspected lesions of the:

• Deep digital flexor tendon
• Ligaments within the foot
• Coffin joint
• Navicular bone
• Any other bone, joint or ligament up and including the upper aspect of the canon bone and the knee

We use MRI under general anaesthetic primarily for evaluating the brain and nerves of horses that show signs of neurological disorders, such as blindness, mentation changes, ataxia etc.

A horse undergoing standing MRI of the foot

Sagittal MR images of in T1w GRE (A1 & B1) and fat suppressed images (A2 & B2) of the feet of two horses. The images on the left (A1) show the normal appearance of the navicular bone, with a smooth palmar border (arrow) and dark (hypointense) signal in fat suppressed images (circle, A2). The right images (B1) shows a horse with severe navicular bone disease, note the large defect and irregularity of the palmar border (arrow). Additionally, there is bright (hyperintense) signal within the fat suppressed images (B2), consistent with a bone oedema like lesion (circle).

Transverse MR image of the distal limbs of two horse at the level of the middle phalanx (just above the coffin bone) in T1w GRE (A1 & B1) and in T2w FSE (A2 & B2). The images on the left show the normal dark (hypointense) appearance of the deep digital flexor tendon in both sequences (A1 & A2). The images on the right show a severe lesion of the tendon, with marked increased (bright) signal intensity and enlargement of the tendon (B1, B2).