October 19, 2012
For many of us, ultrasound technology can be summed up as “the machine, the myth, the legend.” This article strives to demystify a valuable imaging tool that may be more within veterinarians’ reach than they first believed.
When Charles Maloy, president of E.I. Medical Imaging in Loveland, Colo., makes a veterinary sales presentation, “The two questions that come out of their mouth every single time are: ‘What’s the price?’ and ‘How do I use the darn thing?’” he said.
Ultrasound education is increasingly available and, while the equipment remains a substantial investment, “You can get systems with full capability, including cardiac imaging packages, for about half the cost from as recent as three to four years ago,” said J.K. Waldsmith, DVM, president of Vetel Diagnostics in San Luis Obispo, Calif.
Very simply put, ultrasound produces an image made from reflected sound, causing an echo and showing up in varying shades from white to gray on a screen. It’s used frequently for abdominal and cardiac studies in small-animal medicine, and on musculoskeletal and reproductive evaluations in horses.
Applications are constantly expanding. Dr. Waldsmith said new high-frequency probes even enable veterinarians to ultrasound all ocular structures.
“It’s an incredible tool. It’s made a huge difference in our ability to diagnose,” said Kathy Spaulding, DVM, diplomate of the American College of Veterinary Radiology.
A clinical radiology professor at Texas A&M University College of Veterinary Medicine, Dr. Spaulding specializes in abdominal ultrasound.
“I think ultrasound has become one of the major diagnostic tools in how we practice medicine. Not all practices use it, but most progressive practices do,” she said.
Spaulding said the “first wave” of ultrasound use in veterinary medicine began in universities in the late 1970s and early 1980s. One of her earliest ultrasound lectures as a professor at North Carolina State University was to an audience of three: one student, one practitioner and one anatomist.
“Now, people are hungry for it,” she said. “People realize how valuable it is,” and some veterinarians are adding ultrasound technology to stay competitive in business.
“The equipment and the price have improved significantly. You don’t necessarily have to have a $200,000 unit to have a good image,” Spaulding said.
Noting that ultrasound originally was used a lot for confirming pregnancies, she said: “We’re constantly improving our knowledge of how sound interacts with tissue. We’re also learning our limitations.”
Ultrasound is good for studies of muscle, bladder calculi, all abdominal organs, thyroid and heart, Spaulding said. It’s not as good on bones or lungs (although the surfaces can be imaged), but air and gas surrounding a structure will obstruct the image. In the thorax, ultrasound can detect fluid in the pleural space or loss of air in the lungs, she said.
With the advent of ultrasound imaging, “We don’t do nearly as many contrast studies as we used to,” Spaulding said, such as upper GI, intestinal tract, or cystograms in the urinary tract. “For instance, with a bladder tumor, you can use ultrasound and you don’t have to put an iodine contrast agent in the bladder.”
Ultrasound can act as a guide for procedures such as biopsy, fine-needle aspirate and follicle aspiration, said Erika Wierman, DVM, sales manager for E.I. Medical Imaging.
“The more we learn about the pathophysiology of disease, the more we are able to use ultrasound to identify problems as well,” she said. “While magnetic resonance imaging and computed tomography scan can also be used for internal examinations, only ultrasound—and perhaps fluoroscopy, to some extent—allow real-time evaluation of these structures.”
With all that said, “It’s still a difficult and challenging field,” Spaulding acknowledged. “You can teach the science of it easier than you can teach the art of it, and the art is practice, practice, practice.”
Texas A&M veterinary students are taught an instructive course on ultrasound in the third year, with a two-week hands-on course in the fourth year, she said.
“And more and more people are coming back and doing continuing education in ultrasound,” she noted.
Waldsmith figures it takes about 200 cases before the practitioner is really comfortable with normal anatomy and image artifacts.
“Once that level of confidence is achieved, tissue abnormalities, including measurements, are much more apparent,” Waldsmith said.
“There’s a learning curve there, definitely,” Spaulding said. “If you send an image out for interpretation, you’ve got to have a good image of the organ, a knowledge of anatomy, correct machine settings and knowledge of diseases that affect that organ. You have one image, and if it isn’t good, it’s hard to interpret.”
Spaulding suggested that an ultrasound rookie might break down learning into manageable stages.
“First, learn to recognize bladder calculi and tumors. Next, shunts. As you learn, you use it for more and more different types of things,” she said, marveling: “When I’m doing an ultrasound-guided cystocentesis or tumor aspirate, there’s nothing like watching that needle go exactly where you want it to go and missing vital structures, like vessels.”
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