By Meghan Lepisto, Publications and Media Relations Manager, University of Wisconsin School of Veterinary Medicine
Scientists at the University of Wisconsin–Madison have created a diagnostic imaging tool that fills a longstanding, unmet need in the diagnosis and treatment of a variety of conditions facing horses and other large animals. Named Equina, it is the first helical computed tomography (CT) scanner on the market to vertically scan the lower legs of a standing, sedated large animal. The system is also the first dual-purpose standing CT machine; this means it can scan up and down a patient’s legs and move horizontally to scan the head and neck.
The first Equina machine was installed for evaluation in the winter of 2018 at UW Veterinary Care, the teaching hospital of the UW School of Veterinary Medicine (SVM), and the service is now available for patients. Already, more than 150 horses have been scanned at the hospital using the new system. This has led to findings undetectable by earlier methods, including a brain tumor, an orbital tumor behind the eye, and diseases of the feet, teeth and sinuses.
“The CT has changed the way we can evaluate lameness and orthopedic injury in the distal limb and has virtually replaced radiography (X-rays) as the gold standard diagnostic for disease of the teeth and skull,” says Dr. Samantha Morello, clinical associate professor of large animal surgery at the SVM.
CT provides improved imaging of bone and soft tissue compared to traditional X-rays and allows for easier and faster imaging. While X-rays yield a two-dimensional version of a three-dimensional object, which can lead to obscurities, CT “removes that layer of ambiguity” through three-dimensional, cross-sectional images, explains Dr. Ken Waller, clinical associate professor and section head for diagnostic imaging at the SVM.
In addition, because a horse can remain standing in the scanner and only requires sedation, there’s no need for general anesthesia – a cost savings for the client and safety advantage for the patient and hospital personnel.
The technology has also proven beneficial for referring veterinarians in the region and for those pursuing training at the SVM.
“This is a great opportunity to bring novel technology to the state and to our school,” says Dr. Waller.
The idea for the machine began with Dr. Peter Muir, an orthopedic surgeon at the SVM who for more than two decades has studied bone biology and the mechanism that leads to stress fractures in racing greyhounds and thoroughbreds. The types of career-ending fractures suffered by racehorses and other performance horses often begin as small cracks or stress lesions in the bones of the lower leg, which are hard to detect on radiographs, but can be easily seen on CT. Muir realized that having new technology to screen for the injuries would be an important innovation.
In 2013, Dr. Muir approached Rock Mackie, then director of medical engineering at the Morgridge Institute for Research, with the idea of developing a vertical CT scanner for horses. The end result “is sort of CT in reverse” says Dr. Muir. Cutting-edge robotics precisely move a 2,000-pound CT scanner around the horse. The intellectual property behind the technology was patented by the Wisconsin Alumni Research Foundation.
The system continues to be refined based on clinician feedback. Units have also been installed at the University of Minnesota College of Veterinary Medicine and the University of Melbourne’s U-Vet Werribee Equine Centre in Victoria, Australia.
Equina’s creators hope that as the technology becomes more widely adopted, horses exhibiting lameness or other signs of injury can be screened for early signs of a break and treated before the fracture becomes a serious clinical problem.
Dr. Muir and others at the SVM are pursuing multiple areas of clinical research around standing CT to advance equine studies. Asto CT LLC, the company founded at the university that developed Equina, is also exploring potential applications for the machine in human medicine, for example, in radiotherapy.