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Meet the Veterinary Specialists: The Radiologist

Pet Column for the week of August 2, 2004

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Services - Veterinary Profession

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Kim Marie Labak
Information Specialist

Editor's Note: As people have become more health-conscious, and bonds between humans and their pets have deepened, the demand for veterinary specialties such as dermatology, behavior, pathology, and surgery has risen. The following is part of a series exploring these specialties and the University of Illinois veterinarians who practice and teach them.

Veterinary radiology, like its human medicine counterpart, is central to diagnosing and solving many medical problems. Dr. Stephen Kneller, veterinary radiologist retired from the University of Illinois Veterinary Teaching Hospital in Urbana, was board certified in radiology in 1972, when the field had only around 30 specialists. Today, there are over 200 board-certified veterinary radiologists.

As in many veterinary specialties, most technology and equipment in veterinary radiology comes from human medicine. Like "people doctors," veterinarians can use X-rays, CT scans, ultrasound, nuclear imaging, and MRIs to help diagnose medical conditions. Dr. Kneller says that although special veterinary X-ray machines are designed differently to accommodate positioning of animals, the equipment in the teaching hospital used for ultrasound, CT scans, and most X-rays is identical to the equipment found at the local "people hospital."

X-rays, or radiographs, and CT scans (CT stands for computed tomography; they're also known as cat scans, from computed axial tomography) are very similar. They both give veterinarians a picture based on density of tissues, so dense materials such as bone or metal will show up bright white, while soft tissues and fluid appear gray, and gas appears dark or black.

The difference lies in the perspective; radiographs give a front-to-back or side-to-side view through the body, while CT scans can give pictures of horizontal "slices" of the body. These sliced views are particularly useful when looking at the head, since the skull is comprised of many layers of bones that blur together in a standard radiograph.

Ultrasound can give more specific information than radiographs or CT scans, since it can differentiate between different types of soft tissues. Not only does ultrasound show the difference between bone and tissue, but it can differentiate between normal tissue and some damaged or cancerous tissue. Ultrasound is primarily used for cardiology and for examining abdominal organs such as the liver, spleen, and kidneys. The disadvantages of ultrasound are the limitations on how deeply into the body it can image and the difficulties in anatomic orientation.

Magnetic resonance imaging, or MRI, is used primarily for neurology to visualize the brain and spinal cord and at some institutions has virtually replaced the procedure known as the myelogram, in which a radio-opaque material that shows up on x-rays is injected into the space surrounding the spinal cord.

Nuclear medicine is a field of imaging in which an isotope is injected into a patient, usually intravenously. Damaged or newly formed bone will attract this isotope, and radiologists can see bone lesions, such as stress fractures, that would not show up on a normal radiograph. This procedure is used mostly on racehorses.

Most general practice veterinarians take X-rays and interpret them at their practice, but often specialists are consulted for second opinions as well as for more advanced techniques including CT scans, ultrasounds, MRIs, and nuclear imaging. These specialists have more than just fancier equipment; they also have specialized training and more specialized experience.

Board certification in radiology, as well as many other specialties, requires graduation from an accredited veterinary college, three to four years of residency training under the tutelage of at least two board-certified specialists, and acceptable performance on board examinations. The University of Illinois currently has three board-certified veterinary radiologists on staff, and has trained nine radiology residents.

Dr. Kneller explains that your average general practice veterinarian may see four or five radiographic cases a day, or as few as one every other day, whereas the radiology team at the university's Veterinary Teaching Hospital averages more than 15 radiographic cases, 15 ultrasound cases, and 2 to 6 MRI and CT cases every day.

Radiology is very subtle and complex, and Dr. Kneller says "it requires reconstructing three-dimensional animals from flat images. This requires putting together knowledge of anatomy, physiology, and the physics of radiological imaging." Specialists work as part of a team with general practice veterinarians and other specialists to diagnose and solve medical problems.

For more information about veterinary radiology and other veterinary specialties, visit the AVMA Web site at and click on "Veterinary Specialty Organizations."