Thermal Imaging for Veterinary Applications

Circulatory patterns expressed as heat emitted from an animals body can be "visualized with a high 

level of accuracy and sensitivity using an infrared camera. 

Lack of symmetry between corresponding sides of a patient's body can reveal important information 

about whether current blood flow is normal, or requires a closer look. Blood flow patterns that are 

either increased, decreased or lack symmetry can offer early indications of health problems.

Anatomical Imaging such as radiography and Ultrasound reveals a tissue’s structure. 

Physiologic imaging on the other hand, is a function of metabolic action and reveals 

the body’s response to a change in structural integrity, environment or state of health. 

Because physiological imaging captures the body in a dynamic state, changes that 

might indicate an impending problem might appear prior to anatomic disruption.

Thermography (or thermal imaging) is considered physiologic imaging because 

as the animal's metabolism changes, the circulatory pattern associated with it will

 express those changes in the form of temperature patterns. 

For example a sore tendon heats up, that fact can be measurably discerned.

Equine Thermography

Thermography is a qualitative assessment of temperatures. The infrared camera measures temperature automatically and displays a thermal image with color variations corresponding to different temperatures. A "hot spot" might indicate inflammation or increased circulation. Hot spots generally are seen in the skin directly overlying injury. A cold spot is a reduction in blood supply usually due to swelling, thrombosis, or scar tissue.

 Infrared cameras are highly sensitive and reveal minute variations in temperature whether they are medically relevant or not. Because a variety of factors can influence surface temperature, image "artifacts" must be accounted for when using a thermography camera, so experience is a key to accurate diagnosis. If a patient’s legs have been wrapped for instance, or blisters or liniments have been used, they will draw additional blood flow to the site and show up as areas with increased heat. In addition to recognizing artifacts, thermal symmetry is the rule – the comparison of one anatomic area with the same area on the other side (e.g., outside foreleg to outside foreleg).

Inflammation

Thermography can be used to determine if there is inflammation in an area that is sore on palpation, or to detect an area of increased blood flow in the absence of pain (subclinical inflammation). Because weight distribution and locomotion is a function of checks and balances, lameness in the horses is rarely expressed as a single isolated problem. Thermography also helps in detecting secondary areas with associated problems.

Horses have evolved to supress any outward indication of lameness (i.e. structural weakness) as long as possible, making accumulative or low grade injuries difficult to detect in the early stages. The sensitivity of thermal imaging however can reveal inflammatory changes in tendons and joints as much as two weeks before clinical lameness is apparent.

Muscle injury

A very valuable use of thermography is in detecting muscle injury as it can display focal areas of inflammation associated with a muscle or muscle group. In addition, muscle atrophy and circulatory disruption due to scar tissue or edema can also be seen before they become apparent clinically. Atrophy can often be recognized as an area of consistent decrease in circulation when compared to the opposite side.

Nerve injury

Nerve injury due to direct trauma or secondary to another injury or disease can also affect blood flow and can often be more readily visualized with thermography compared to other diagnostic modalities.

Preventive medicine

Thermography also can be used to assess the vasculature and blood flow to tissues before and after exercise.

Other uses include pre-purchase examinations, saddle fit, as a monitoring tool during training, pre-race examinations, hoof balance, healing assessment following tendon injuries etc. In the hands of an experienced practitioner, there are many valuable uses for this non-invasive, but reliable diagnostic tool.