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Dagmar Berner (Senior Lecturer in Equine Diagnostic Imaging) and Freddie Dash (Lecturer in Equine Diagnostic Imaging) spoke to Clinical Connections about what a new scanner means for patients, research and training.

A new state-of-the-art advanced CT scanner has been installed in the Equine Referral Hospital so we can better diagnose and treat conditions in our equine referral patients. The new Qalibra CT scanner also has benefits for veterinary education, advanced clinical training and research into conditions affecting horses.

This machine brings several big improvements, including that with this new design the horse stands on the ground and the CT machine moves. Thus the horse is much more likely to be still during examination and the images are of better quality. Additionally, the acquisition time is much shorter than before, reducing the likelihood of motion artefacts, further enhancing the quality of images.

Another significant difference is versatility of the system, which can be lowered to a height that enables us to scan limbs of standing sedated horses. This allows us to scan up to and including the carpus and tarsus without the need for general anaesthesia (GA).

The new CT has a larger diameter bore and with the horse anaesthetised this will enable us to visualise the entire forelimb and hindlimb as well as the cervicothoracic junction, pelvis and sacroiliac joints. Many of these areas are difficult to evaluate with other diagnostic imaging modalities. Being able to acquire images of these areas not only helps us to diagnose abnormalities more precisely but also helps to gain knowledge about certain conditions, for example of the cervicothoracic junction, which is an area that little is known about in horses.

There is a common misconception that CT is not useful for the soft tissues, however the soft tissue detail is very good with our new system. Conditions such as tendon and ligament injuries are well visualised. Therefore, we envisage more and more horses will undergo CT examination for suspected soft tissue injuries as well.

Welfare issues  

Getting an accurate, prompt diagnosis can allow for precise, swift treatment, and by catching the disease early we can improve outcomes for our patients. An example would be the diagnosis of cartilage defects as part of osteoarthritis. Diagnosticians were previously limited to radiographs, standing MRI and ultrasound, which all have their limitations. However, now using CT in combination with a radio-dense dye in the joint we can diagnose these changes earlier and with greater accuracy.

With our new CT scanner we are able to do these examinations in a standing fashion without general anaesthesia (GA), which is a significant development. The biggest problem in horses we still face, even with the best anaesthesia teams available, is the increased risk to horses during the recovery period after GA. Owners are consequently reluctant to let horses have GA for just diagnostic purposes. The new CT allows us to diagnose disease earlier and without horses requiring GA to be CT scanned.

Veterinary education, advanced training and research     

Our new CT system has massive benefits for students, residents and interns in giving them a better understanding of certain disease processes, as well as improving options for visualising the anatomy of the distal limbs. Limb CTs historically were not that common, apart from for surgical planning. However, now that we can do these examinations in standing sedated horses we will, as a profession, gain more knowledge about disease processes in this area.

Residents will be working on many more CT cases, which enables them to greatly improve their knowledge and experience with this modality. The 3D image also helps veterinary students better understand anatomy and gives them a better appreciation of disease processes.

Rose’s case  

This case highlights the usefulness of CT for orthopaedic issues in horses. Rose had a CT scan of her lower limb which, thanks to the new scanner, could be done with her standing up and using sedation only.

Rose is a 15-year-old Warmblood mare that presented to RVC Equine with the history of an acute onset left forelimb lameness. This occurred following landing from a jump approximately three weeks prior. The lameness had improved with strict rest, but not resolved.

Once at the hospital, Rose was trotted in a straight line on a hard surface and found to have a grade 2/10 left forelimb lameness. She was reactive to palpation over the deep digital flexor tendon and straight sesamoidean ligament in the proximal pastern area. Regional anaesthesia of her foot had no effect, but when the pastern was included with an abaxial sesamoid nerve block, the lameness was abolished.

Radiographic examination was normal, and ultrasound revealed no findings that could convincingly explain the lameness. Therefore, advanced imaging was recommended and, in this instance, CT with positive contrast venography was performed.

This revealed two main findings. First, an active desmopathy of the straight sesamoidean ligament, demonstrated by a contrast enhancing core lesion within the substance of this structure (green arrows) and contrast leakage into the digital flexor tendon sheath. Second, a synovial mass affecting the dorsal border of the deep digital flexor tendon within the proximal recess of the navicular bursa (blue arrows), likely representing either torn tendon fibres or a granuloma.

This information enabled the imaging and surgery teams to work together to provide a specific tailored rehabilitation regimen for Rose, incorporating class IV laser therapy, and provide the best chance of a recovery.

This is a good demonstration of the use of CT for complex cases where other imaging techniques have not provided a definitive answer. It also highlights the ability of CT to detect soft tissue injuries and its power to image a large area of anatomy quickly.

The new CT scanner was funded thanks to donations from trusts and legacies facilitated by the RVC’s charity, the Animal Care Trust, which raises funds with the aim of improving animal health and care through clinical practice, education, and pioneering research.