Thermography in equines:

What does the Infrared Thermal Imaging Camera capture and measure?

Thermography captures and measures temperature (Radaelli V. et al., 2014); the symmetry of thermal patterns in different anatomical structures, mainly soft and musculoskeletal tissues.

The way thermography can capture and measure temperature is because infrared (IR) cameras have an electronic sensor device capable of capturing heat, emitted as infrared energy and invisible to the human eye, on a visible light screen.

What is inflammation and why is it important?

Inflammation is an important part of the defense system and is essential for survival.

Inflammation occurs naturally when the body reacts defensively to any harmful stimulus.

When inflammation occurs, there are a series of complex chemical reactions.

According to the duration and the physiological response mechanism, inflammation can be divided into two types: acute and chronic. For the purposes of my work, I will focus on the chronic condition because the acute condition usually resolves within hours following the injury and is not within my professional competence.

With expert hands we can visualize and palpate the signs of the inflammation process - vasodilation, increased blood flow, smooth muscle and relaxation of arterioles, among others - but with the IR camera we can capture the range of temperature increase after an injury due to the chronic inflammatory process.

Therefore, it is important to understand the physiology of the inflammation process because when it goes from acute to chronic - when the acute response is not able to eliminate the causal factor/harmful stimulus - we can do it through images and establish different treatment protocols for the improvement of the horse.

How does thermography work?

Thermography works by capturing the infrared energy emanating from the horse due to its body temperature (Soroko M. et al., 2018).

This form of infrared energy is not visible to the human eye (Radaelli V. et al., 2014), so a camera with electronic sensors capable of capturing this form of energy is needed.

With the IR camera software, the images are processed and reflected in a visual image, capable of being seen and interpreted by the human eye.

The sensors convert the infrared emissions into a visual graphic representation showing different colors - which will represent different temperature ranges - which a specialized thermography technician is able to analyze.

Each temperature range is assigned a color. Generally, "hot" spots are commonly characterized as red or white, while "cold" spots are black or blue, although the color palette can be altered by the operator.

Before an anatomical area can be considered abnormal, multiple thermographic images of the area of interest must be taken from at least two views 90° apart.

What are the benefits of using thermography?

Personally, and in relation to my profession - osteopath - and the horses I work with - polo ponies -, I consider that there are three main benefits in the use of thermography:

1. Being able to identify early signs of inflammation (Soroko M. et al., 2018) so that the veterinarian in charge of the horses I work with can carry out further investigations.
2. Monitoring and tracking the rehabilitation process
3. Show the owner the results of physical therapy (before/after) through pictures

What type of injury can we detect with thermography?

The following list is not exhaustive and we must not forget that in many cases what the IR camera detects are signs of inflammation prior to the pathology. A temperature difference of more than 1° between symmetrical regions is considered sufficiently significant for further investigation. Pathologies and lesions that we can detect with thermography:

1. Location of a generalized lameness (Turner, 1991).
2. Tendon injuries
3. Navicular disease
4. Abscesses on hooves
5. Foot balance
6. Joint inflammation
7. Stress fractures
8. Muscle damage
9. Back pain (Von Schweinitz, 1999)

Are there any contraindications to the use of thermography?

None, since it is a non-invasive imaging method that is performed without contact, without penetrating radiation, or emission of ultrasonic waves, nor is it necessary to place the animal in an electromagnetic field, unlike other research and diagnostic methods (Radaelli V. et al., 2014).

Examination and protocols.

It is easy to make mistakes in the interpretation of thermal images due to the influence of external factors, so it is imperative to work with an established protocol and a controlled environment to promote accuracy in the interpretation of images (Soroko M. et al., 2018).

With the following protocol we can create valid thermographic images:

1. Stability of the animal with a competent handler - if necessary, use physical restraints to stabilize the animal without any type of drug containment - (Radaelli V. et al., 2014).
2. Control the ambient temperature of the room - consider a room without sunlight or any extraneous radiation (Radaelli V. et al., 2014).
3. Considerations regarding excess fur, hair and sweat of the animal
4. Remove limb supports and topical medications at least one hour prior to evaluation.
5. Correct equipment and calibration settings. Perpendicular angle of 45°, animal in the center of the screen, good focus.
6. Review the anatomical area of interest in 90° separate planes.
7. Symmetry: If there is any concern or doubt about the heat pattern in an anatomical section/structure, capture both anatomical sides and compare them.
8. Capture and document that the asymmetric heat pattern remains constant over a period of 4 to 6 minutes. This helps confirm that the region requires further investigation.

Why do I choose to use thermography for professional polo ponies?

Polo is a high-speed, impact sport with macro and micro repetitive movements that place demands on joint integrity and stability, and it is also known that every polo pony owner is afraid of tendon injuries. Thermography has been reported to be sensitive enough to detect soft tissue injuries to the flexor tendon or suspensory ligament two weeks before the horse becomes lame, muscle damage and the “forgotten” back pain of the horse (Von Schweinitz, 1999), which I believe are sufficient clinical reasons, due to the demands of the game, to have access to a non-invasive tool such as this, capable of giving an instant indication of these conditions.

Early detection of injuries (Soroko M., et al., 2018) in polo ponies can make the difference in the season.

References:

1. Dietrich Graf von Schweinitz, 1999, Thermographic diagnostics in equine back pain. ScienceDirect doi.org/10.1016/S0749-0739(17)30170-0
2. Radaelli, V. et al., 2014, Use of thermography techniques in equines: Principles and applications, Journal of Equine Veterinary Science, 34, 345–350
3. Soroko M., Howell K. 2018 Infrared Thermography: Current applications in equine medicine. Journal of equine Veterinary Science. doi.org/10.1016/j.jevs.2016.11.002
4. Turner T.A. 1991, Thermography as an aid to the clinical lameness evaluation. Vet. Clin. N. Am. Equine Pract. DOI: 10.1016/s0749-0739(17)30502-3