On a blustery January morning at the Brookfield Zoo, all is quiet inside the world-renowned zoo’s 20,000 square-foot animal hospital. The beds are empty, save one where doctors are spaying a female rabbit. But with approximately 3,500 animals in their care, members of the zoo’s veterinary team are well aware that the situation could change at any moment.
When an animal is ill or needs a preventive check-up, diagnostic imaging is of the utmost importance. Fortunately the zoo, located just outside of Chicago, houses not only a sophisticated advanced medical diagnostic imaging suite — equipped with one of the world’s largest CT scanners — it is also the only zoo or aquarium in the world with a full-time radiologist on staff.
Marina Ivančić, DVM, DACVR, joined the staff in 2016, just before the zoo received a donation of a new large-bore 16-slice CT scanner from a local hospital. The equipment, a considerable upgrade from the zoo’s previous scanner, is capable of imaging animals up to 660 pounds, such as adult gorillas, tigers or dolphins.
“I look at every type of imaging on every animal there is,” said Dr. Ivančić, who also consults through teleradiology with veterinarians in zoos and aquariums across the globe. “We do CT scans of hundreds of varying species, ranging in size from a tiny 45-gram violet-backed starling to a 290-kilogram okapi. Some patients as small as 2-gram dart frogs undergo whole-body radiography using our dental unit!”
Along with the new CT scanner, the imaging suite is equipped with portable ultrasound units, two direct digital radiography units, dental radiography and a C-arm fluoroscopy unit, also added in 2016.
The zoo, which opened in 1934, has built its imaging suite over time. It has had a CT scanner since 2009, digital radiography since 2007 and ultrasonography since the early 1990s, Dr. Ivančić said.
All of the zoo’s diagnostic imaging equipment is standard technology normally used by humans and is donated by area hospitals.
An infinite number of conditions can be detected with diagnostic imaging, including pulmonary disease, kidney or bladder stones — a common issue in domestic cats and otters — and cancer. Procedures are commonly, but not always, performed under sedation.
“Some animals allow us to conduct diagnostic imaging evaluations without restraint or even sedation,” Dr. Ivančić said. “We can perform voluntary ultrasound in animals such as dolphins, great apes and giant anteaters. We are able to monitor the health of a fetus during pregnancy, perform echocardiography to look for heart disease, and/or complete routine whole-body ultrasound to assess general health without the need for sedation, restraint or anesthesia.”
For those that do need sedation, the zoo’s new CT scanner drastically increases the speed of scanning, decreasing the time an animal needs to be sedated. During a CT scan under sedation, the animal is secured in place on the table and monitored closely by a veterinary anesthesiologist who is also board-certified in zoological medicine.
Dental procedures, which are performed under anesthesia, can be completed more precisely and quickly with CT guidance.
“With onsite CT, we can nearly instantaneously obtain critical measurements and describe anatomical variation to a dental specialist to help guide nerve blocks and endodontic procedures,” Dr. Ivančić said.
For example, the veterinary teams used CT to help guide endodontic procedures in one of the zoo’s sloth bears.
Imaging equipment can also be an enormous help as a preventive tool for any of the nearly 400 different species at the zoo.
One recent example is Arie, a California sea lion unable to live in the wild who was taken in by the Brookfield Zoo. During a routine preventive CT scan in September 2016, the team noticed an unusual conformation — a swelling that was determined to be scoliosis of the spine. The CT scan also provided a baseline to monitor for associated degenerative arthritic changes in her spine.
“This helped us better understand why she was stranded in the wild and was unable to survive,” Dr. Ivančić said. “We can now provide her with a safe environment, companionship with other sea lions, and decades of care.”
In another case, ultrasonography was used to image an umbilical hernia in a pygmy hippo, facilitating diagnosis of intestinal entrapment, which allowed veterinarians to pursue emergency exploratory laparotomy and save the animal’s life.
Another zoo leading the way in veterinary radiology is the San Francisco Zoo & Gardens, an urban oasis nestled against the Pacific Ocean.
Home to more than 1,000 exotic, endangered and rescued animals representing more than 250 species, the zoo has been offering onsite imaging care for its animals for more than 40 years.
Because the zoo’s imaging volume is not high enough to warrant a staff radiologist, some clinical diagnostic imaging is done in-house while other exams are performed off-site at veterinary clinics, said Graham Crawford, DVM, chief of veterinary services at the zoo, which was established in 1929.
“We use radiography and ultrasound on all animals, from frogs and birds to big cats, bears and large-hoof animals like giraffes,” Dr. Crawford said. “We do not have in-house MRI or CT, so when the need arises, we can take animals out of the zoo to local specialty veterinary clinics that have that equipment.”
For MRI and CT, animals are placed on the gantry and slid into the scanner, he said.
“We can fit animals up to the size of a 550-pound male lion or a 350-pound male gorilla onto our stationary radiology unit in the hospital,” Dr. Crawford said. “For larger animals, like rhinos or giraffes, we have a mobile radiology unit that we can take into the exhibit.”
Over the years, both zoos have benefitted from substantial advancements in imaging the animals they house and care for — progress which will only continue as technology progresses.
“I’ve seen the advancement from analog to digital and wireless radiography and the standard use of ultrasound in general practice,” Dr. Crawford said. “CT and MRI technologies are now readily available, but are generally found in specialty veterinary practices.”
At Brookfield Zoo, which houses many rare and endangered species, the advanced imaging equipment also plays a role in the conservation of wildlife. Through its advanced medical imaging suite, the zoo has built a comprehensive database of normal medical images that serves as a global resource for zoos and wildlife medicine.
“We can glean an enormous amount of data about an animal’s health in less than one minute, which is invaluable since data available for reference is limited with endangered and rare species,” Dr. Ivančić said.
Imaging will continue to play a critical role in zoological medicine, which is on the cusp of other significant advancements.
“Zoological and wildlife medicine has increasingly embraced advancements in technology in the last several decades, and diagnostic imaging is an enormous component of this progress,” Dr. Ivančić said.
Dental procedures, which are performed under anesthesia, can be completed more precisely and quickly with advance CT guidance. Above: Graham Crawford, DVM, chief of veterinary services at the San Francisco Zoo, performs dental work on a tiger at the zoo. Image courtesy of the San Francisco Zoo
Veterinary radiology is a growing field, with more than 600 members in the American College of Veterinary Radiologists (ACVR), a nonprofit organization of veterinary specialists in radiology and radiation oncology founded in 1961.
Candidates must complete a doctor of veterinary medicine (DVM) degree in veterinary school and become board-certified through the ACVR, followed by a one- or two-year internship and multi-year residency under the supervision of an ACVR board certified radiology diplomate.
ACVR sponsors four specialty societies: the Veterinary Ultrasound Society, the Society of Veterinary Nuclear Medicine, the CT/MRI Society and the Large Animal Diagnostic Imaging Society.
For more information, go to ACVR.org.
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