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See Spot. See Spot’s
Films. A Look at Veterinary Imaging You’ve heard the old radiology joke about the cat scan and lab[rador] report, but what really happens in veterinary imaging? Ultrasound and x-ray are the mainstays, but most modalities find their way into specialty care for animals. When little Mikey falls off his bicycle and hurts his arm, an x-ray at the local emergency department or imaging center may be necessary. Depending on the suspected injuries, there may be a CT or MRI for the boy. But what happens if Mikey’s pet dog or cat suffers an injury. How does imaging factor into the treatment options? It turns out that many of the imaging modalities used on human patients also examine our four-legged, furry, or feathered friends of the animal world. And even PACS is playing an increasing role. In the Spotlight According to reports published after the accident, Barbaro dislocated his ankle, or fetlock joint, and suffered major fractures of his cannon and long pastern bones and a minor fracture of the sesamoid bone in his right hind leg. Barbaro was subsequently taken to the University of Pennsylvania’s George D. Widener Hospital for Large Animals at the New Bolton Center in Kennett Square, Pa. Soon after, an x-ray image of Barbaro’s leg with more than 20 screws visible was released to the media. Since May, Barbaro has undergone several surgeries—including placing a titanium plate and nearly 30 screws to set his fractures—and endured a case of laminitis in his previously uninjured left hind hoof. The laminitis, or swelling of tissue inside the hoof, forced doctors to remove a significant portion of the hoof wall of Barbaro’s left hind leg; there is little room for swelling inside a horse’s rigid hoof. America watched regular reports on the horse’s care to see whether he would survive or need to be euthanized. Barbaro’s prognosis has improved greatly since that time, including taking short walks outdoors as part of his recovery and rehabilitation. Famous Images “Digital radiology has been the hot new equipment in the past five years, with many veterinary vendors now marketing it,” says Armbrust. “CT and MRI are in most academic institutions and large private specialty clinics.” CT and MRI are among the modalities used on site at The Animal Medical Center in New York City, says Anthony J. Fischetti, DVM, MS, DACVR, department head of diagnostic imaging. The center, located in Manhattan’s East Side, deals mainly with small animals. Veterinarians typically fall into one of two broad specialties: small or large animal specialists. According to the Web site for The Animal Medical Center, the facility’s first CT scanner was purchased in 1984, followed by an ultrasound machine the next year. A radiation therapy suite was established in 1987 and additional technology has been added since then. MRI is most often used for neuroimaging such as determining the causes of seizures and other neurological deficits, brain tumors, and inflammatory brain disease and for some vascular diseases and spinal cord compressions, among other ailments, according to Peter V. Scrivani, DVM, Dipl ACVR, an assistant professor at Cornell University College of Veterinary Medicine. “Nuclear medicine is also available at most academic institutions and specialty [especially horse] private practices,” says Armbrust. “Nuclear medicine has been used for more than 20 years.” For example, nuclear scintigraphy is frequently conducted in racehorses to determine a source of lameness, explains Scrivani. Also, says David S. Biller, DVM, DACVR, professor and head of radiology at Kansas State, some common nuclear medicine procedures include bone scans in horses and small animals and thyroid scans, especially for older felines. The procedures involve using the same contrast agents as in humans. Ultrasound & X-ray For the most part, though, radiographs are the first type of image used for treating an animal. “Radiographs are made on all parts of the body for both small and large animals,” says Armbrust. Fischetti says radiographs are ordered for approximately 70% to 80% of The Animal Medical Center’s cases. “We routinely start with radiographs because they give us a nice global image of the chest or abdomen or the extremities and then we make the decision [for further imaging] based on a couple things,” explains Biller. Those factors can include the weighing of risks and benefits in the animal’s treatment and the owner’s ability to afford the cost. Adaptation “Our MRI has a table which accommodates animals to lie on,” adds Scrivani. “For our CT scanner, we had to build a special table that we can lift the horse up on, and this table locks into the couch that moves in and out of the gantry. [The table] actually holds the weight of the horse. There are just minor changes and an understanding of how to sedate or control the animal so they don’t hurt themselves, the equipment, or the people.” “There are also standing MRI units for looking at the distal limbs in horses,” says Armbrust. A CT scanner used for veterinary imaging may require parameter changes such as decreasing the field of view. MRI equipment may require more adaptations, such as finding specific coils for certain body parts, according to Fischetti. There can also be limitations to what portion of a larger animal can be examined through CT or MRI. “Like with a horse, we have a [CT scanner] table that can hold the weight, but we can only fit their head and part of their neck into the scanner,” says Scrivani. “We can’t assess the abdomen of a horse with another modality other than ultrasound.” There can even be challenges with imaging smaller animals. “You get to a point of diminishing return,” says Fischetti. “The gantry hasn’t decreased in size, so you can get images that are very pixilated or noisy,” such as with the spine of smaller animals. “Smallness does make it difficult,” says Biller. “When they’re very small animals, magnification often decreases the overall quality of the image.” Scrivani says the amount of sedatives or anesthesia needed to control an animal for imaging really must be taken on a case-by-case basis. “It really depends on the time of the examination,” says Scrivani. The animal may be under general anesthesia for an MRI but awake for an x-ray or ultrasound. “It really does depend on the nature of the animal,” he adds. “There’s not a lot of risk to the patient other than the risk that’s associated with being under general anesthesia,” Scrivani continues. “So if they’re severely or critically ill, anesthesia for a prolonged examination may not be in the patient’s best interest.” “The main challenge veterinarians face is patient positioning/compliance,” says Armbrust. “For example, you can’t tell a dog to stay still and take a deep breath for [a] thoracic study. Most animals require one to two holders and may also require some degree of sedation or anesthesia. “For ultrasounds, animals may require sedation but less commonly,” adds Armbrust. “For ultrasounds, we generally clip the hair to get good contact.” Why Image an Animal? “The information given to us for both prognosis and diagnosis is immense. Imaging gives the ability to noninvasively evaluate the patient internally,” says Biller. “There’s a tremendous positive impact for our patients, owners, radiologists, and clinicians.” “Imaging has greatly improved patient care,” says Armbrust. “There are many instances where treatment, prognosis, or the next most beneficial diagnostic test is determined from an imaging study. We also do lots of FNA [fine needle aspiration] and biopsies based off our studies. “There certainly would be cases that don’t require imaging, but at our referral hospitals, around 80% of the patients require some sort of imaging,” adds Armbrust. “There is always the risk of radiation exposure for our personnel and the risk of fractious animals—bites and kicks, etc.” Scrivani illustrates one instance where the option of conducting an imaging test must be closely weighed. “Let’s say we suspect a very small fracture in a horse and we want to do a CT to find it,” says Scrivani. “But [after the scan] we have to wake up that horse and the horse could injure itself while being woken up, so you really have to weigh the risks of ‘do we really want to anesthetize this animal that has a nondisplaced fracture and take the chance that it might become a displaced fracture if we can’t fix it or if it would heal fine with just stall rest?’” Scrivani notes that Barbaro’s case illustrated the opposite situation. “That horse had an obvious fracture,” he says. “You needed to do the imaging or you weren’t going to do anything for that horse. That was a life-or-death decision.” What can also present problems is whether a facility has the necessary equipment and the trained personnel to use it. “We see a lot of people who have access to a CT scanner, but they’re not really trained on how to use it,” Scrivani says. No Insurance Here Veterinarians routinely deal with the duality of animals as both companions and assets. That duality can get tricky when an animal’s potential economic value is high. The case of Barbaro illustrates this point. While his racing career is over, the Kentucky Derby winner has great potential value as a breeding stallion, which raised questions about the care provided to the horse. Dean Richardson, DVM, the veterinary surgeon who led Barbaro’s surgical team, addressed that aspect in the press conference following the initial surgery on the thoroughbred. “…I made a big point about how the optimal outcome for the horse is that he be salvaged for breeding,” Richardson said. “And some people are taking that the wrong way. I want everyone to understand that if this horse were a gelding, these owners would have definitely done everything to save this horse’s life.… I’ve known the Jacksons [Barbaro’s owners] a long time...this horse could have absolutely no reproductive value and they would have saved this horse’s life.” Barbaro’s situation is an extreme example. Far more often, the emotional and economic decision plays out where a dog or cat owner will pay a few thousand dollars (or more) for high-end imaging and specialty care for a family’s beloved pet. Conversely, a feeder calf that will be raised for beef and then slaughtered and may bring roughly $750 at market simply won’t receive high-end treatment. That balance between companion and commodity value is nearly always a factor in animal medicine. “We had a donor for our MRI unit, so we can keep the cost down,” explains Scrivani. “There is an increased cost for the client, but we’re also providing better care for their pets. You will find the entire gamut of that. People who often come to Cornell are prepared to spend the big bucks and they want the best care. A lot of this [cost concern] is weeded out in the primary care facility.” “When they come to see a specialist, they’ve kind of committed to the cost,” says Fischetti of pet owners. “They’ve already kind of been filtered through. They know ‘this is going to cost me, but I want to do it.’” — Tracy Meadowcroft is an editorial assistant at Radiology Today.
Anthony J. Fischetti, DVM, MS, DACVR, department head of diagnostic imaging at The Animal Medical Center in New York City, says the center adopted PACS approximately eight months ago, with digital radiography following roughly two months later. He says having the PACS helps with archival, retrieval, and multiple viewings in a hospital that is very busy and where space is certainly a commodity. The PACS also allows for searching a large database of clinical cases for teaching and clinical research. David S. Biller, DVM, DACVR, professor and head of radiology at Kansas State University College of Veterinary Medicine, says PACS has been in use at his facility for approximately two years. “It wasn’t a difficult switch to filmless,” says Biller. “It was the only way to go.” All CT and MRI images taken before the PACS was installed have been added to the system. The facility’s ultrasounds have been backed up but not converted to PACS images. Prior radiographs generally have not been added to the PACS; however, some cases have been digitized so they are available for teaching purposes, says Biller. “We don’t ever have to be concerned that films and images are misplaced, lost, or destroyed, and that has been such a relief for me,” says Biller—images can easily be converted to a JPEG format and sent to referring veterinarians. Surgeons can also bring up images on monitors while performing operations. Monitors and LCD projectors are also used during rounds with veterinary medical students, explains Biller. Having a PACS also allows radiologists from the Kansas State University College of Veterinary Medicine to read images transmitted from a practice in Omaha, Neb., at the college’s facility. As is the case with many imaging modalities, there is little difference between animal and human PACS. CoActiv Medical Business Solutions developed both ExamPACS and PACS4VETS; the main difference between them is a few fields, including species, owner, and breed. Both programs have the same programming and functionality. — TM
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September
25, 2006
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