Introduction to Standing Equine MRI
With over two decades of experience in Magnetic Resonance Imaging (MRI) and a commitment to advancing equine veterinary care, Hallmarq pioneered the world’s first and only Standing Equine MRI (sMRI) machine. Now considered the gold standard by equine vets around the globe, this unique imaging modality brings the same diagnostic capability to equine clinical practice as human MRI. With optimal horse health at the forefront of every design decision, standing MRI is unparalleled in providing images of soft tissue in a safe, effective, and affordable procedure.
Diagnostic in over 90% of cases, Standing Equine MRI is one of veterinary medicine’s most valuable non-invasive imaging technologies. By visualising slices through tissue, MRI equipment—when used in horses—can quickly and precisely localise damage to soft tissue structures such as tendons, ligaments, and muscles to identify the specific cause of lameness, all without general anaesthesia.
MRI is increasingly used in equine practice for evaluating musculoskeletal structures (MSK) and injuries. It provides an unparalleled evaluation of soft tissue structures over all other imaging modalities. MSK MRI allows for detailed examination of injury or inflammation of soft tissue structures such as tendons, ligaments, and muscles. When evaluating complex structures such as the equine hoof, MRI helps provide invaluable information.
In this comprehensive Guide to Standing Equine MRI, we answer your questions on how this technology works and the benefits and capabilities of Standing Equine MRI in diagnosing and treating lameness in horses.
How Standing Equine MRI Works
Standing Equine MRI is a low-field MRI procedure performed while the horse remains standing. This specially designed scanner is safe for the horse and handler and is carried out with gentle sedation for the patient. By visualising slices through tissue, standing MRI can quickly and precisely localise damage to both bone and soft tissues without the need for general anaesthesia.
So, how does it work? MRI technology relies on strong magnetic fields and radiofrequency pulses. These magnetic fields align the protons inside the body’s hydrogen atoms. When radiofrequency pulses are applied, they disrupt this alignment. As the atoms return to their normal state, they emit captured signals to create cross-sectional images that show the differences between various tissue types.
Although classed as a low field, the magnet used in a standing MRI machine is incredibly powerful at 0.27 Tesla. However, as MRI does not use ionising radiation, the magnetic field or the radiofrequency waves are not harmful to your horse or people, making it safer for repeated use.
Preparation for Standing Equine MRI
The connection between the horse and the image is invaluable, and looking at the lameness pattern on the day of the scan benefits the outcome. Your vets will discuss the case with the referral practice ahead of the day and provide as much useful information about the case as possible. It is also important for the vets to see and evaluate the feet. Information on the shoe, trimming, balance, and any distortion to the coronary band will help them interpret everything they see on the MRI images.
However, ensuring the patient is well-prepared, and as relaxed as possible before a standing MRI will pay dividends. In particular, time spent on preparation of the feet before the scan is essential for successful imaging.
- Most practices take one or two X-rays before performing the MRI to help check for clenched (metal) fragments, which can cause artefacts (distortion) on the images.
- Ahead of the scan, the horse’s shoes must be removed. In most cases, just two shoes need to be removed: the leg to be scanned and the adjacent leg.
- Any metallic objects will distort the image, and steel horseshoes could become stuck to the magnet, putting the horse and handler in danger.
- The horse’s legs should be clean and dry and free from any blue or purple antiseptic sprays that will affect image quality if not removed.
- Once at the veterinary practice, the horse should be given time to stand in the stall, urinate, and settle before going into the scan room.
- Once the horse is in the scan room, the end goal is a comprehensive set of high-quality sequences taken from the region of interest in a reasonable time.
Procedure Overview
When it comes to diagnosing equine lameness, acquiring the best possible MRI images starts long before the patient enters the MRI room.
- As an extremely safe diagnostic imaging modality, MRI poses no risk to the patient
- Your horse will not require general anaesthesia but a small amount of gentle sedation will be administered to help it remain calm throughout the procedure
- An experienced vet will choose the appropriate type of sedation based on the individual patient’s health condition and the duration of the scan
- They will closely monitor the horse’s vital signs throughout the procedure to ensure safety
- Once prepared for scanning, the sedated horse is walked into the MRI scanner, and the lame leg is placed between the poles of the magnet
- To enable the capture of quality images, a radiofrequency coil is fitted around the injury site
- The operator makes any adjustments to ensure that both the patient and system magnet are in the right place
- Careful positioning of the limb to be scanned is vital if clinically diagnostic images are to be taken
However, even the most docile horses will sway or move slightly when standing, and this movement changes the shape of the joint as the horse shifts its weight distribution. Hallmarq’s Standing Equine MRI incorporates our award-winning motion correction software. This technology – unique within the equine industry -is specifically designed to compensate for any slight movement of the horse’s limb throughout the imaging process. It helps enable faster scan times to provide detailed clinical images of each horse seen by the vets.
MRI scanning can be a slow process to obtain clinically diagnostic images. Typically taking 1-3 hours, most horses can be seen on a day-patient basis. If scans of multiple areas (e.g. feet and fetlocks) are required, your vet may recommend that the horse stay overnight and be imaged over two days to avoid large amounts of sedation on one day.
Applications and Uses
With no risk to the horse, Standing Equine MRI is far safer than conventional or “down” MRI. Where imaging can only be done with the horse recumbent (or lying down), a general anaesthetic will always be required. General anaesthetic even in a healthy horse carries some risk; 1% of horses [1] suffer complications, which can be life-threatening.
MRI is typically the best choice for diagnosing bony and soft tissue disease when more conventional imaging techniques are negative, unclear or access is difficult. An additional benefit to imaging the limbs while the horse is standing and gently sedated is that it allows internal structures to be assessed while they’re load-bearing, which is usually when the lameness is most apparent.
As the gold standard in diagnostic imaging, standing MRI is proven to deliver a definitive diagnosis in over 90% of lameness cases. Chief amongst them is the ubiquitous navicular disease. MRI is the only modality to distinguish between the multiple causes of navicular disease or heel pain.
Historically, navicular disease was diagnosed when abnormal changes to the navicular bone were seen on X-ray. With the wealth of additional information MRI gives us about the bones and soft tissues within the hoof capsule, we now know navicular disease or syndrome can cause foot pain due to several different problems.
Structures such as the impar ligament and the insertion of the deep digital flexor tendon (DDFT) are extremely difficult, even impossible to assess without MRI. Understanding how damage to these structures results in navicular disease has enabled vets to direct treatment more specifically and, therefore, more effectively in these cases.
The applications and uses of standing MRI are far broader than just navicular disease. The equine foot is very complicated, and it’s important to evaluate as many structures as possible. The dynamic process that MRI enables is key to diagnosis, especially in specific areas where anatomic detail is required, such as:
- Dorsal margin lesion on the DDFT
- Distal border fragments on the navicular bone
- The flexor cortex to see fine areas of fluid accumulation signalling early pathology
- Coffin joint cartilage and fibre cartilage on the back of the navicular bone
Where other imaging modalities might fail, MRI identifies subtle lesions such as bone inflammation and early onset degenerative joint disease earlier than ultrasound and radiography. In addition, when additional assessment to radiography is necessary (e.g. penetrating injury, fracture), standing MRI is an invaluable aid to surgical planning and offers vital benefits in guiding treatment plans for rehabilitation. Monitoring patient progress optimizes treatment and speeds time to a return to competition.
A case studies library is available here detailing each patient’s history, their specific injuries, what scanning with standing MRI found, potential diagnosis, treatment, and prognosis. Clinical images are included to illustrate the findings and annotated to highlight the area of concern.
Advantages and Limitations
As with every modality available in equine medicine, MRI has its advantages and limitations. No single diagnostic method gives us all the answers. It’s important to remember, therefore, that the information provided by any diagnostic imaging technique must be examined in the context of the individual patient.
Advantages
Apart from being an incredibly safe advanced imaging tool, MRI is unmatched in its ability to reveal details in soft tissues. Unlike other modalities, it can ‘see’ through the hoof capsule, providing invaluable information about the foot and revolutionizing the diagnosis of conditions such as navicular disease and DDFT injuries. Although less common nowadays, mainly due to awareness, education, and the use of MRI as the gold standard in diagnosis, a DDFT injury is the most common site of damage in the foot identified by standing MRI scanning of sport horses.
“Hallmarq’s MRI has revolutionized the way foot lameness has been diagnosed in thousands of cases over the last 20 years. Excellent image quality facilitates accurate diagnoses, appropriate treatment selection, and formulation of a prognosis.”
Dr Sarah Taylor, BVM&S MSc PhD Cert ES(Orth) DipECVS DipECVSMR MRCVS, The University of Edinburgh. The Royal (Dick) School of Veterinary Studies
For racehorses in training, fast work at high speeds places the fetlock – particularly the back of the joint – under extreme forces. This repetitive, extreme shock absorption by the joint can lead to traumatic lesions affecting the subchondral bone and/or cartilage. While the lesions can be severe, horses can appear only mildly lame, ‘work out’ of the lameness, or even appear sound but not performing as well as expected. If left unchecked, these lesions can lead to catastrophic breakdown of the fetlock joint, ending the racing career of an individual or resulting in fracture and – in the worst-case scenario – emergency euthanasia.
An MRI diagnosis is far more cost-effective than multiple rounds of the examine-treat-repeat loop. Most UK insurance companies now cover the costs of specialist treatment, including Standing Equine MRI. Some will ask that you cover a certain percentage of the costs, and other policies might exclude certain conditions or treatments. Always check with your own insurance company first.
Limitations
Likely costs associated with a Standing Equine MRI scan and incurred by the horse owner will be:
- Transporting your horse to and from the referral clinic
- The expertise of staff who are specifically trained in MRI scanning
- The cost of sedation for the horse
- Pre-MRI X-rays to detect clench (metal fragments)
- Stabling if needed, although – for the most part – your horse will be seen on an out-patient basis
- A radiologist report written by a specialist who examines and interprets the MRI images to provide a diagnosis
Along with the associated costs, there is also the question of accessibility. For some horse owners, the nearest Standing Equine MRI may be too far away to sensibly consider transporting their horse for treatment. For others, however, making that journey is well worth the investment. With a clear diagnosis, you can make the best decision for your horse and agree on a targeted treatment plan to ensure their safe return to work.
Post-Procedure Care
Post-procedure care of equine MRI patients is essential to their recovery, and the advice of your vets should be followed carefully:
- After the MRI scans are complete, your horse will remain at the veterinary practice for careful monitoring during their recovery period
- Ensuring a return to normal temperature, movement, and gut motility is important
- Food should be slowly reintroduced, and ideally, the patient should pass faeces
- Your horse, once ready, can safely return home and – in most cases – on the same day
- Once home, strenuous activity should be avoided for at least the first 24 hours or upon the guidelines provided by the referring vet
- The large number of images obtained during the MRI scan will need to be reviewed and interpreted by an experienced radiologist
- In most cases, a comprehensive report will be produced within 3-5 days and copies will be sent to you and your referring vets
Comparing Standing MRI to Other Diagnostic Tools
As with all diagnostic imaging technologies, standing MRI has advantages and disadvantages. Here, we look at the practical application of the available modalities most commonly used to aid lameness diagnosis in equine practice. Each has its unique benefits, and deciding which to use depends on various factors, including the type of issue, cost, and the details each imaging method can capture.
Radiography (X-ray)
X-ray is often the primary method of assessing bone condition. It has the advantage of being relatively inexpensive and can often be used without bringing the horse into the clinic (ambulatory). However, its main limitation is that the two-dimensional images produced show shadows of overlying bones. This makes it hard to completely evaluate the complicated structure of the carpus and tarsus, where multiple bones overlap. Occasionally, a horse might be diagnosed with a fracture via X-ray but not respond to treatment as expected. In these cases, an MRI might reveal that nearby soft tissue structures have also been affected and require treatment. Certain fractures or pre-fracture bone changes can also be missed on X-rays.
Magnetic Resonance Imaging (MRI)
Unlike X-rays, MRI can detect fluid in the bone that is often the precursor of a fracture. This is particularly common in racehorses since their carpal and fetlock joints are under intense strain during fast work. Spotting the damage early allows changes to the horse’s management to avoid potential injury. Although some of the more severe lesions can be seen on X-rays, often, by the time they are visible, the disease has progressed. Due to its superior ability to identify subtle changes earlier in the progression of the disease process, detection with MRI enables rest periods and training modifications to be made before clinical disease terminally affects the horse. MRI can also be used to monitor the return to health of the joint before performance training is resumed.
Ultrasound
Ultrasound is widely used to image soft tissues in human and veterinary medicine. It’s a relatively cheap technique, but the grainy images can be difficult to interpret and rely heavily on the operator’s skill. Ultrasound waves will not pass through bone, so the technique is particularly difficult to use around the bones of the carpus or the splint bones in the upper leg. Standing MRI gives far more detailed information on the condition of the horse’s leg’s tendons and ligaments, and seeing slices taken in multiple directions allows a complete evaluation of the area.
Computed Tomography (CT)
CT scans use X-rays and computer processing to create cross-sectional images of the body. CTs are highly effective for imaging bone and mineralized tissue and for detecting fractures. The CT scanner rotates around the patient, capturing multiple photos of the area of interest from different angles. These images are then used to build a detailed 3D reconstruction of the internal structures. CT scans are faster than MRI, a key benefit of its technology, particularly in emergencies. However, MRI’s superior imaging capabilities allow for the detection of problems that CT might miss.
“Standing MRI allows us to accurately diagnose the cause of lameness in the vast majority of cases where standard diagnostic techniques fail to give us the answer. It permits the selection of appropriate treatment methods, whereas, without it, we would often have been guessing.”
Tim Mair, BVSc, PhD, DEIM, DESTS, DipECEIM, MRCVS, Bell Equine Veterinary Hospital, Kent, UK
The Future of Equine MRI
The use of MRI in Orthopaedic imaging has been a reliable modality for many years. As with any modality, the ultimate goal of low-field MRI – when used in equine practice – is to aid effective lameness diagnoses. Increased knowledge and image acquisition techniques continue to grow as specialists in the field of equine lameness diagnosis look for new and improved ways of benefiting the patient.
With the image quality key, software enhancements that minimize artefacts and allow for the horse’s natural sway continue to be developed. The field of veterinary diagnostic imaging is undergoing significant transformation with the integration of artificial intelligence (AI) tools. Their application brings the benefit of reduced scan times and improved image quality. For the equine patient, reduced scan times mean less time spent under sedation and a quicker return to health.
Conclusion
Key findings:
- MRI is cost-effective and has a multi-modal ability to identify soft tissue and osseous pathology
- MRI is unparalleled in providing images of both soft and bony tissues
- MRI allows detailed cross-sectional imaging of the target structures using multiple planes to depict up to 500 images per hoof
- MRI images the region of interest in slices orientated in any 3D plane so that a lesion can be visualized without superimposition of adjacent structures
- MRI does not use ionizing radiation, reducing the biological hazards associated with its use compared with that of radiography or computed tomography
- MRI is sensitive enough to depict evidence of pre-fractural damage, hairline fractures, and singular lobe ligament damage
- MRI distinguishes water from fat, highlighting areas of pathology such as inflammation and bruising in a way that X-ray, CT, ultrasound, and nuclear scintigraphy cannot
- MRI provides multiple views, allowing you to appreciate the full extent of the injury
As access to MRI becomes increasingly available in veterinary hospitals and speciality centres, the applications for use continue to grow. In cases where traditional diagnostic methods may not cause lameness, standing MRI can offer a more comprehensive view, often helping to achieve a definitive diagnosis essential to patient care.
“Our MRI unit offers significant benefits over our previous imaging capabilities, such as radiographs and ultrasound. It offers the highest soft tissue imaging detail possible and unlocks certain diagnoses for us now that were never possible previously. This enables us to make the most accurate diagnosis for our equine patients and means our treatment plans can be more specific and targeted. Since installing Standing Equine MRI at our practice, we have been able to offer a higher standard of care to horses who come to see us“
Andrew Jones, Clinical Director, and Surgeon CVS Endell Equine Hospital, UK
Despite MRI being the gold standard in lameness diagnosis, it is not infallible, and 100% sensitivity and specificity are impossible. But, with MRI proving diagnostic in over 90% of lameness cases, its efficacy is not to be ignored. MRI provides the best technique available to the equine vets under “reasonable” conditions. Additionally, without the need for general anaesthetic, the procedure is risk-free to the horse and, therefore, less expensive for the owner and vet than the treat-repeat loop so often sought.. For specialists in equine surgery, its impact as a tool to aid pre-surgical planning is key.
Hallmarq is proud to be pushing the boundaries of what can be achieved with advanced diagnostic imaging. Our Standing Equine MRI machine enables imaging of the distal limb without the need for general anaesthesia this has improved safety for horses, made advanced imaging more affordable and accessible to owners, and increased the number of horses that can undergo advanced imaging. All this combines to increase patient welfare and veterinary knowledge.
FAQ’s
- What is a standing equine MRI scan?
Standing Equine MRI is one of veterinary medicine’s most valuable non-invasive diagnostics.
- How does the standing equine MRI work?
The standing equine MRI uses a specialized magnet and imaging system designed to accommodate a horse’s lower limbs while the animal remains standing and awake, eliminating the need for general anaesthesia. It captures detailed cross-sectional images of bones, joints, and soft tissues by creating a strong magnetic field and using radio waves to generate high-resolution images, allowing vets to diagnose conditions without invasive procedures.
- Why would my horse need an MRI?
Your horse might need an MRI to diagnose conditions that are difficult to detect with other imaging methods like X-rays or ultrasounds, such as soft tissue injuries, subtle bone fractures, or joint issues. MRI is particularly useful for identifying problems in the horse’s hooves, tendons, ligaments, and joints, helping to pinpoint the cause of lameness or discomfort when other diagnostic tools are inconclusive.
- Is a standing MRI safe for my horse?
Yes, a standing MRI is generally safe for your horse. It is a non-invasive procedure that does not require general anaesthesia, reducing the risks associated with sedation and allowing the horse to remain calm and comfortable.
[1] Morgan, Jessica M., Helen Aceto, Timothy Manzi, and Elizabeth J. Davidson. ‘Incidence and Risk Factors for Complications Associated with Equine General Anaesthesia for Elective MAGNETIC RESONANCE IMAGING’.Equine Veterinary Journal, 7 November 2023, evj.14026. https://doi.org/10.1111/evj.14026.
