A Multitude of Modalities

The next diagnostic options generally include MRI, nuclear scintigraphy (“bone scans”), or computed tomography (CT) scans. While beneficial, each of these modalities has its limitations. The tool with the broadest application is a CT scan, which produces three-dimensional images. A CT scan can be used to detect changes to bone that might not be visible on X-rays as well as soft tissue structures. CT scans are often used to diagnose lameness issues (including occult and complex fractures), as well as sinus, head, and neck problems.

While helpful, these scans generally are not without risk. Traditional CT scans are performed on a fully anesthetized horse. The area needing to be scanned is then placed inside the machine while the horse is lying on a large gurney. The size of the opening of the machine limits how much of a horse can be scanned. Typically an adult horse can only be scanned up to his hock or knee.

However, horse owners now have another CT tool at their disposal that is fast, able to be used on additional body parts, and less fraught with possible complications: The Equina by Asto CT.

High-Tech Imaging

Developed at the University of Wisconsin-Madison, the Equina is the first dual-purpose standing CT. The machine can be used to vertically scan the lower legs and it can be used horizontally to scan the head and neck — all on a standing, sedated horse.

To scan the limbs, a horse is lead on to a platform at ground level and the limbs needing imaging are comfortably positioned within the “target ring.” At the press of a button, a circular structure rises from the platform and surrounds both front or hind legs. Unlike CT machines used in human medicine, which have limited capabilities on what they can scan, the entire opening of the Equina can produce a scan. This allows the horse to stand anywhere that is comfortable on the target ring to have his legs scanned.

Additionally, traditional machines produce large amounts of radiation, requiring the sedated horse to be in the room alone. The Equina machine, however, is self-shielded and emits exceptionally low levels of radiation. This allows veterinary staff to remain in the room with the horse and observe him closely, ensuring they are on hand to react rapidly if he needs help.

Dr. Sabrina Brounts, a professor in large animal surgery and equine sports medicine and rehabilitation at the University of Wisconsin-Madison, says that the entire process can take as little as 15 to 20 minutes. That includes getting the horse ready and sedated, scanning him and leading him back to his stall. The horse is typically sedated with acepromazine, detomidine, or xylazine. The scan itself takes less than a minute and if all goes well, a trained team can scan three to four horses an hour.

Brounts finds one of the Equina's unique capabilities incredibly helpful: the CT can provide scans of  both limbs at the same time, regardless of if the horse is weight bearing or not.

“That gives you the information to compare both limbs [affected and unaffected] to find a cause for issues,” she explains. “The horse stands exactly like it normally does … If you had to scan one limb at a time, you would never be able to create the exact circumstances for the limbs.”

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