Scintigraphy is a technique in which an injected form of radioisotope can be imaged by a gamma camera, which takes "pictures" of the radiation given off by the isotope. As the isotope travels and is absorbed by various systems of the horse's body, it can be observed and correlated to offer diagnostic information. Essentially, this diagnostic test detects increased blood flow to an area. The radioactive isotope is used as a marker, and a picture of where the isotopes concentrate (due to increased blood flow to an injured area) is made available to the veterinarian via computer. Scintigraphy is a non-invasive technique whereby the short-lived gamma-emitting radioisotopes are used to image body tissue, including bones and soft tissue.

Scintigraphy has become common in screening for microfractures that can develop into more severe injuries. This technique is used most extensively in racehorses. Even though many trainers have embraced the use of scintigraphy, the diagnostic tool is not available everywhere. Since scintigraphy requires the use of radioactive material and trained personnel, there has to be a special facility available within a short distance from the track, which isn't always the case. Scintigraphy isn't a lameness meter; someone has to interpret the information. Roughly a third of the time scintigraphy doesn't show the answer to a horse's lameness problem because the problem is in soft tissue, which is not visualized as well. For best results, scintigraphy should be used in combination with a lameness exam and other diagnostic tools.

Scintigraphy requires specialized handling and facilities because of the danger of radioactive isotopes used in the procedure.

Ultrasonography (ultrasound)

Ultrasound takes a safe sound wave, and through a machine, converts it into a real time picture that the veterinarian can interpret. This modality allows a veterinarian to see internal structures of the horse without any invasive procedures. Looking at an ultrasound image is almost like watching a black and white television.

There are a number of different ultrasound units available, but they perform basically the same task. Types of heads differ depending on what body part is to be imaged, and the power of the equipment is critical to its use.

Ultrasound has revolutionized medicine because it is a safe, portable, diagnostic modality that does not harm the horse, handler, or veterinarian. This non-invasive diagnostic technique visualizes the internal structures of the body by means of sound (echo) reflections--ultrasound.

The use of ultrasonic sound for diagnosis and treatment in human and equine medicine is not new. Most horse breeders, for example, are familiar with the use of diagnostic ultrasound to detect and monitor reproductive problems and pregnancy. Sport horse owners in large numbers have seen ultrasound employed in diagnosing soft tissue injuries, such as damaged ligaments and tendons. Ultrasound also can be used to evaluate the kidneys, liver, lungs, heart, or any soft tissue area, and to an extent it can be used to detect bony problems such as osteomyelitis or early fractures. In large part, ultrasound's use in bony problems depends on the veterinarian's skill and the machine itself.

Ultrasound is limited by the depth of penetration. A tendon probe only allows sound waves to travel inward a short distance. If a different scan head is used on the machine, your veterinarian can visualize deeper tissues and structures. Depth of penetration goes up to approximately 30 centimeters, or 15 inches, into a body. While ultrasound has limited applications for bone, it does have magnificent applications in soft tissue diagnostics.


Thermography is a diagnostic tool that measures heat. A heat detection device, which looks like a video camera, is used to scan the horse and determine variations in heat patterns. These variations can help a practitioner determine areas of increased or decreased blood flow, or alterations in normal heat patterns.

While thermography has been around for quite some time, the thermographic equipment that has evolved in the last two years has greatly improved the effectiveness and usefulness of this diagnostic tool. For instance, new thermographic equipment can be used in many different environmental settings, and it has a greater capability of helping veterinarians diagnose problems at an earlier stage. New equipment is fast, portable, and non-invasive. Because of how this diagnostic tool has evolved, horse owners probably will be seeing more of this tool used and it will offer greater accuracy in diagnosing.

This equipment shows veterinarians "hot spots" or increased body temperature in a horse's soft tissue and skin, usually one of the first signs of damage. The images vary in color from shades of black, blue, yellow, green, and red, with some white. Most veterinarians use a color palate with red indicating a "hot spot" that could have been caused by injury, and shades of blue indicating cooler temperatures. The increased blood flow is due to the body's bringing in more blood to an injured area, which brings in more helpful cells to aid the body in taking away debris and repairing the damaged tissue. Increased blood flow to an injured area can occur before clinical signs of pain and lameness appear.


Radiography directs beams of penetrating radiation to a body part and generates an image that allows visualization of areas that attenuate the beam differently than neighboring areas. Radiography is the use of X rays, or gamma rays, to view the internal structures of the body in order to locate problems, such as fractures. While not effective on soft tissue, X rays are common when looking at bones.

This is a non-invasive diagnostic technique with which most horse owners are familiar. It also has become common to use radiography in pre-purchase exams in order to detect problems before a horse is purchased.

The objects to be X rayed are placed before a special camera. The camera sends out a certain type of radiation, which produces a negative that is developed into film in a dark room similar to one used in a camera shop. When the film is developed, it is viewed with a light behind it, enabling the veterinarian to make a diagnosis. Taking X rays requires specialized handling because of the danger of radiation exposure.

Magnetic Resonance Imaging (MRI)

Due to a horse's large size and the equipment's limited viewing area, magnetic resonance imaging is not used very often for horses other than for legs and heads. However, a new, portable, hand-held MRI device currently is being developed by Magnavu, of California, that would make this diagnostic tool much more suitable for horses. This smaller device will be like putting a pair of calipers on a horse's limbs that allow you to go up and down on the limbs to get an MRI image. When this portable MRI device is available for use in the field, it will greatly enhance this diagnostic tool's value for more horses.

MRI offers exquisite imaging, especially of soft tissues. The details are unlike any seen on conventional X rays or ultrasound. Magnetic resonance images differ from X rays in that X rays are associated with the absorption of X ray energy, while MR images are based on proton density and proton relaxation dynamics. These vary depending on the tissue that is being examined and reflects its physical and chemical properties.

MRI is used extensively in human medicine to view internal organs for the diagnosis of cancer and other diseases. Advanced magnetic core imaging agent technology is based on the design and manufacture of extremely small, uniform, polysaccharide-coated superparamagnetic iron oxide particles. When placed in a magnetic field, such as an MRI machine, these particles become strongly magnetic, then lose their magnetism once the field is removed. These image enhancement products offer the potential for earlier, cost-effective diagnosis and management of disease through improved visualization of normal versus diseased tissue.

MRI provides information that differs from other imaging modalities. Its major technological advantage is that it can characterize and discriminate among tissues using their physical and biochemical properties (water, iron, fat, and extravascular blood and its byproducts). Blood flow, cerebrospinal fluid flow, and contraction and relaxation of organs, both physiologic an pathologic, can be evaluated. MRI produces sectional images of equivalent resolution without moving the patient. The ability to obtain images in multiple planes adds to its versatility and diagnostic utility of this tool, and offers special advantages for radiation and/or surgical treatment planning.


The endoscope has evolved from the rigid, inflexible tube originally used in medicine to today's flexible equipment with highly sophisticated imaging equipment. There are ridged ones-- laparascopes-- currently used for looking inside of body cavities. Flexible endoscopes have fiber optics that bends light so a practitioner can look through the eyepiece and see the image. The light is cold, not hot. When the endoscope first appeared, it used hot light, which meant a veterinarian was limited in the time spent in the body due to burning of the tissue.

A video endoscope has a television and a fiber optic component in it that greatly improves the image and transmits the image to a screen for easier viewing by more than one person. Video systems are available for the regular fiberoptic systems. The video systems are vital to treadmill endoscopic studies because they allow researchers to view inside the horse while it is running. Any cavity that the machine can be introduced into can be scoped, such as the uterus, bladder, or respiratory system.

"Scoping" is a procedure where a tube-like viewing apparatus (the endoscope) is inserted into an orifice or body cavity for the purpose of examining the internal portions of that cavity. High-speed treadmill endoscopy has been an invaluable tool for determining causes of poor performance and abnormal upper respiratory noise in athletic horses. While gross structural abnormalities can be diagnosed by resting endoscopy and other methods, it is the dynamic abnormalities that take place during strenuous exercise that cannot be appreciated by any other method but treadmill endoscopy.

About the Author

Tim Brockhoff

Tim Brockhoff was Staff Writer of The Horse:Your Guide to Equine Health Care from 1995 to 1999. His degree is in Agricultural Communications from the University of Kentucky, and his equine experience is with American Saddlebreds.

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