Radiography, Scintigraphy, and MRI: Benefits and Pitfalls

 Radiography, Scintigraphy, and MRI: Benefits and Pitfalls.

  • Radiography, Scintigraphy, and MRI: Benefits and Pitfalls

Likely the most commonly used diagnostic modality in horses, radiography has become even more important with the advent of digital results.

Photo: Courtesy Dr. Carter Judy

Today, veterinarians have the ability to peer inside horses’ bodies and see what’s causing a limp, swelling, or pain. The use of radiography (X rays), nuclear scintigraphy (bone scan), and MRI in horses is practically commonplace. Unfortunately, choosing which tool to use and interpreting its results is not always black and white.

During the 2014 American Association of Equine Practitioners (AAEP) Convention, held Dec. 6-10 in Salt Lake City, Utah, Carter Judy, DVM, Dipl. ACVS, discussed some benefits and pitfalls of these three imaging techniques.

“Each imaging modality has its own strengths and weaknesses,” said Judy, who practices at Alamo Pintado Equine Medical Center, in Los Olivos, California. “Knowing the caveats of each will help determine what modalities to use and how to interpret the findings.”

Nuclear Scintigraphy Veterinarians can perform this simple and relatively noninvasive procedure with the patient standing under light sedation. It reveals areas of active bone remodeling, and practitioners typically use it to identify physiologic changes in bone and soft tissue, said Judy.

 

Scintigraphy is often used when the region of lameness is unknown or indeterminate using routine techniques such as nerve blocks.Photo: Courtesy Dr. Carter Judy

 

“Scintigraphy is often used when the region of lameness is unknown or indeterminate using routine techniques such as nerve blocks to localize the area of pain,” he said.

Its downside is that you don’t always know what’s causing the bone remodeling, and it’s less effective at identifying soft tissue lesions than MRI.

MRI This tool is quickly becoming more commonly available to equine veterinarians, said Judy. Practitioners can use either a low-field MRI system in the standing patient or a high-field system in an anesthetized patient.

“Magnetic resonance imaging is used when the area of pain is known but the cause has not been well-established using other techniques,” Judy explained.

 

MRI is used when the area of pain is known but the cause has not been well-established using other techniques.Photo: Courtesy Dr. Carter Judy

 

One of the challenges of using MRI is that some findings identified using this technique might not be visible on other modalities, and vice versa, he said. Also, it can be more difficult to interpret than scintigraphy or radiographs.

Radiographs Likely the most commonly used diagnostic modality in horses, radiography has become even more important with the advent of digital results.

“While some soft tissue changes can be ascertained, the focus of radiographs is to provide an evaluation of the bony structures of an object,” Judy said.

He explained that radiography’s pitfalls include the fact that it’s use is primarily limited to bone problems; its images are two-dimensional representations of a three-dimensional structure; and it’s less sensitive than, say, MRI.

Take-Home Message All three of these modalities are user- and interpreter-dependent. Also, said Judy, it’s important to consider them complementary: “Negative results on one modality do not preclude the absence of a problem in the patient, and an alternative imaging technique may provide more insight into the pathology of a particular patient.”

ABOUT THE AUTHOR

Alexandra Beckstett, The Horse Managing Editor

Alexandra Beckstett, Managing Editor of The Horse and a native of Houston, Texas, is a lifelong horse owner who has shown successfully on the national hunter/jumper circuit and dabbled in hunter breeding. After graduating from Duke University, she joined Blood-Horse Publications as Assistant Editor of its book division, Eclipse Press, before joining The Horse.