If you’re a horse person and read equine publications or have shopped for products for your horse, there’s a good chance you’ve seen a thermal image. But what is a thermal image really? What is it used for and does thermal imaging really have benefits?
An infrared thermal imaging camera identifies temperature distribution on the surface of a horse’s body based on metabolic processes that occur beneath the surface. So what does that mean? All objects emit energy, most of which is not visible by the naked eye. Thermal imaging cameras make the invisible visible by displaying thermal patterns.
A thermal scale starts at black, which indicates cold, and then progresses to white, which is the hottest point of the scale. When imaging a horse, the most common colors you’ll see are red, yellow, green, blue, purple.
What do we look for when interpreting thermal images?
When doing equine thermal images, we look for three primary things:
Inflammation – There will always be areas of red and even white on a horse’s thermal image. That’s because horses are obviously living things that have vascular flow, muscles, nerves, bones, and other soft tissue. There are areas on a horse that should show red or white on a thermal image, perhaps because it’s a vascular area or a part of the horse’s anatomy where the coat or skin is thinner. However, when there are areas which display red or white which are not supposed to display that thermal pattern, it’s a red flag, potentially indicative of injury.
Insufficient Circulation – As there are areas of a horse’s body that should be warmer, there are also areas where it’s appropriate to see a cool pattern. For example, there is very little blood flow in a horse’s legs, so they typically show up purple and blue on a thermal image. For this reason, a horse should be mildly worked either on the lunge line, in a round pen, or under saddle so that circulation is pushed through the legs to see a pattern with better blood flow to identify issues. There are times where there are areas that should have good circulation, and the thermal patter runs blue or purple regardless. This is another red flag because it means that blood flow is being constricted and warrants further investigation.
Asymmetry – The third and most important thing to be identified in a thermal image is asymmetry. Horses are generally symmetrical creatures – what you see on the right should be present on the left. When looking at thermal images, left to right are always compared. If a horse displays inflammation in an area on one side of the body and not the other, it is indicative of a potential issue. For example, horses infrequently suffer suspensory ligament injuries in both front legs at the same time (although it certainly can and does happen), so when imaging a horse, if inflammation is seen in the left suspensory and not the right, it would be indicative of an injury. If the inflammation is seen in both, the interpreting veterinarian would determine if the thermal pattern were a normal pattern or one that is of concern.
When should thermal imaging be used?
There are four primary applications for thermal imaging:
If a horse has a lameness or injury that is in need of diagnosis, thermal imaging can be used to narrow down or diagnose an area of injury. There are many diagnostic tools out there and the question about what makes each one different is often asked. Below is a table that outlines the most common diagnostic tools, their benefits and disadvantages, and relative cost.
What to look for in an equine thermographer
Thermal imaging is a science, and therefore the images need to be taken and interpreted by a trained professional. The thermal imaging process is akin to when a person gets an x-rays. When getting an x-ray, usually an x-ray technician takes the images and those images are then sent to a Doctor of Radiology (Radiologist) for interpretation. With thermal images, a Certified Infrared Thermographer (CIT) will take the images and send them to a veterinarian who specializes in interpreting thermal images. That veterinarian will then write a report with all of the findings. There are some vets that are certified in thermography and offer this service, but usually the person taking the images is different than the vet.
A few things are key in the process and should not be ignored: