CT unit delivers diagnostic clarity

Medical imaging specialist Dr. Kimberly Tryon (left) and medical imaging technologist Debbie Paisley review an image onscreen during a CT study of a calf. Photo: Michael Raine.

Medical imaging specialist Dr. Tawni Silver can’t hide her enthusiasm when she describes the Western College of Veterinary Medicine’s new CT (computed tomography) unit.

In the world of veterinary medical imaging, this machine is like the Cadillac of CT scanners with the ability to simultaneously acquire 16 three-dimensional “slices” or high-resolution images of an animal during each 0.5-second revolution.

“With this machine, we’re on the leading edge of CT imaging for veterinary medicine in Canada,” says Silver. The WCVM’s new unit is available for both small and large animal patients at its Veterinary Medical Centre.

CT is like a three-dimensional X-ray. Once a patient is placed on a table in the machine’s doughnut-shaped gantry, medical imaging specialists send X-rays all the way around the animal’s body and collect multiple images.

The veterinary college’s new CT machine can do this 360-degree imaging in just seconds. For example, Silver says she and her WCVM colleagues can now scan a Labrador retriever’s thorax (chest area) in 15 to 30 seconds while the veterinary college’s old CT scanner took about five minutes to do the same type of study.

“That might not sound like a lot, but the speed makes a huge difference — especially when you’re imaging a moving part of the body like the thorax,” points out Silver.

Every time the animal breathes, there’s chest movement that causes “artifacts” or additional features not normally present on a CT-generated image. With the WCVM’s previous machine, medical imaging specialists had to temporarily stop the patient’s breathing for a certain amount of time so the motion wouldn’t make artifacts on the scan.

As Silver explains, the less time the machine needs to produce the images, the less risk there is for an animal that may already be suffering from traumatic injuries or other health complications. “Now we can temporarily stop the patient’s breathing for 15 seconds without any potential harm to the animal while we take the CT images.”

As well, the faster machine decreases anesthesia time (the norm for all horses and other large animal patients undergoing a CT study) and opens up the option of using sedation on dogs, cats and other small pets.

That means a typical CT study on a dog — including sedation, positioning, the actual scanning and recovery — can be done in less than an hour at the veterinary teaching centre.

The shorter time frame for CT scanning also reduces the time that anesthesiologists must be separated from their patients by a protective lead barrier. “That allows us to get back to hands-on monitoring of the patient more quickly,” explains Dr. Tanya Duke, a veterinary anesthesiologist at the WCVM’s medical centre.

“Plus the less time it takes for the scans, the less likely we are to see anesthesia issues arise in our patients during the CT studies. That cuts down on the need for us to don protective lead gowns and to stay with our patients during the imaging procedure.”

Besides its speed, the new CT machine produces high-resolution images that are exceptional in quality. “CT scans give us a three-dimensional slice of an animal’s body — it’s like slicing a loaf of bread. The narrower the slice, the more accurate the information,” explains Silver, adding that the new CT unit allows specialists to image two-millimetre slices of an animal — a significant improvement over the old unit’s capabilities.

“Now we can scroll through all of those image slices so we can follow a specific blood vessel or we can look at an animal’s entire liver, one slice at a time,” says Silver.

The new technology also allows specialists to develop three-dimensional reconstructions of specific areas. For example, Silver can direct the imaging software to remove the sight of bones so only an animal’s muscles or blood vessels can be viewed. Images can also be used for teaching or easily sent to a referral patient’s primary veterinarian for review.

Since the new CT unit began operating in June 2011, WCVM medical imaging specialists have used the technology for evaluating complicated bone fractures and for viewing animals’ skulls, brains and nasal passages — areas that don’t show up well on conventional X-rays.

“On radiographs, all of the bones in the skull are superimposed on each other, meaning that we can’t see individual bones. But now we can produce a high-quality, three-dimensional view of a patient’s skull.”

CT imaging is also considered the gold standard for identifying tumours in the lung and is vital to planning for pet radiation oncology therapy.

In dogs, the technology is ideal for the detailed visualization of orthopedic disease. It’s also invaluable for describing specific elbow dysplasias, orthopedic injuries and spinal conditions like intervertebral or lumbosacral disease. As a result, the new CT machine has almost made invasive myelograms of dogs’ spines a thing of the past.

In horses, Silver says CT imaging provides specialists with detailed images of the soft tissue beneath the hoof wall — information that’s critical for diagnosing conditions such as navicular syndrome, laminitis, deep digital flexor tendon disease and fractures in equine patients.

“This new CT machine is allowing us to see so much better when it comes to details in soft tissue. MRI (magnetic resonance imaging) is still the gold standard for soft tissue images, but since CT studies can be done so much faster, it’s a valuable option to have available for patients that can’t be under anesthesia for an hour-long MRI study,” points out Silver, who is still learning about all of the new machine’s capabilties.

“Considering all the things we can accomplish with CT scans, this technology is still one of the most economical ways to diagnose a wide range of health conditions in our patients. It really adds a lot to our centre’s medical imaging capabilities.”

For more information, contact the WCVM Veterinary Medical Centre’s Small Animal Clinic at 306-966-7126.