In the hands of a trained veterinarian, infrared (also called thermal) imaging is a powerful tool for finding abnormalities such as infections, tumors, inflammation, fractures and muscle stress or injury in horses, pets and wildlife that may not otherwise be detected by more traditional methods. Infrared cameras detect radiated thermal energy in the 7 – 14 micron (typical for medical purposes) region of the spectrum, just beyond the visible wavelengths. They are passive (do not emit radiation of any type), non-contact, non-invasive instruments that cause little stress in the animal so there is usually no need for sedation. It lets the owner immediately “see” the problem visually and both doctor and owner can then decide if further diagnosis is needed. Thermal imaging is an efficient method of evaluating the overall condition of the animal. It can provide rapid assessments resulting in quick care while eliminating a lot of guesswork.
Animals cannot tell what hurts and instinctively try to hide pain since it is a sign of weakness and may invite attack. Relatively inexpensive thermal imaging can discover a potential problem before it becomes serious or it may indicate that more expensive analysis or treatment is not necessary. While it won’t replace x-rays, ultrasound, MRI’s or physical exams, many vets who are familiar with infrared technology claim it is an extremely useful addition to existing diagnostic equipment and complements other techniques. Infrared cameras are about 40 times more sensitive to heat than the human hand (traditional palpation) and can detect temperature differences of less than 0.05 C.
Thermal imaging measures skin temperature changes and variations that correspond to metabolic changes in underlying tissue. These changes are often caused by an increase or decrease in blood flow; inflammation (warm-increased circulation) or nerve dysfunction (cool-decreased circulation). Increased heat is a major indicator of inflammation in a tendon or joint, hemorrhages or infection. Tumors and lesions also have increased blood flow and thus higher temperatures than the surrounding areas. Nerve damage and circulatory disorders can also be detected with thermal imaging and may indicate problems up to three weeks before clinical signs are apparent. Thermography has been proven to be an effective tool in highlighting areas that need a closer look. Nerve damage and cold limbs are often overlooked because of the lack of heat. The ability to monitor the effectiveness of treatment and recovery is particularly valuable. Other technologies such as MRI or positron emission tomography (PET) scans do not provide the same information as thermal imaging.
When considering infrared equipment, it should be state-of-the art, reasonably priced, contain an uncooled detector and be hand-held for ease of use and portability. Mounted cameras, however, may be used to monitor and evaluate livestock at feeding or milking stations.
Infrared Cameras Inc. (ICI) of Beaumont, Texas manufactures such an instrument in the IR-Pad 640 Veterinary, a winning combination of infrared thermal technology and wide-screen Tablet system with custom calibration for all veterinarian applications. This portable, ultra-rugged indoor/outdoor IR system features a 640 X 512 detector; perfect for capturing high-resolution images in the office or field. It includes ICI’s IR Flash Touch Software which allows complete control over the color palette for viewing the black and white IR images in color scale and contains a full suite of analysis tools as well as Report Building software.
Although this technology can be used on almost any type of animal (including humans) its use first became common in the horse industry, particularly for race horses, and has been a part of the equine health business since the 1960s. It is often used in pre-purchase exams, saddle-fit evaluations, hoof-balancing, abscess detection, pre and post-event physicals, general diagnostics including infection, inflammation, chronic and degenerative diseases, nerve and muscle injury as well as treatment and recovery monitoring.
Infrared cameras simply map warm and cool areas on a horse that might indicate a problem. The horse should be exercised to stimulate blood flow and then rested. The temperature will stay elevated in injured areas for up to 24 hours. While images are often taken by a technician they should be reviewed and interpreted by a qualified, infrared thermography-trained veterinarian. Thermography is particularly valuable in diagnosing neurological problems because it can differentiate between common lameness and rarer vascular problems. This helps eliminate unnecessary treatment and can show whether or not the animal is improving. Early detection of inflammation in tendons allows them to be fixed before rupturing; saving the horse a lot of pain and the owner a lot of vet bills.
Since buying a horse is usually a significant investment, thermal imaging should be part of any pre-purchase exam. It can reveal problems that were missed in the physical exam or were temporarily covered up by recent injections or medication. The overall thermal pattern should show good symmetry. The thermographer must understand basic anatomy and realize that each animal has its own thermal pattern as well, which should be recorded as a baseline for future reference. Patterns are often more useful for evaluations than actual temperatures.
Poorly fitted saddles can cause flinching, dipping, uneven gait and other unusual behavior. The horse’s back should show evenly distributed pressure points (see image…) in order to provide comfort to both the animal and rider.
Lameness is often caused by multiple problems; a series of corrections may be needed to resolve the issue. Thermal imaging helps detect these secondary problems and can aid in the evaluation of the progress being made in several areas of the body. Trainers can see if a horse is well enough to be “pushed” without causing further damage.
Pets can benefit from thermal imaging as well. Dogs have a high threshold of pain so injuries might go unnoticed. They work and play hard so pain and injuries are common: joint stiffness and muscle problems, hip dysplasia (abnormal growth), skeletal problems often related to arthritis, toe injuries and problems from improperly fitting harnesses. Dental problems are often seen when unhealthy teeth appear cooler than surrounding healthy ones because of decreased circulation through the pulp. Increased blood flow to a dog’s leg may indicate injury or inflammation. However, it might be warm because the animal is using it more while staying off the injured one. Viewing the paw prints left on the floor after he moves away may show that one is cooler than the rest (not putting pressure on this paw) and that could result from pain in that leg or portion of the hip.
Cats are especially good at hiding pain so “touching” may not always be a reliable indicator. Most older cats have osteoarthritis, a degenerative joint disease that causes pain to certain degrees. Pain medication is available if the condition is diagnosed, most are not. Thermal imaging can help by showing hot spots in areas such as the back or hip that might indicate centers of pain.
Farmers and ranchers can benefit from thermal imaging by monitoring the general health of their livestock for many of the before mentioned conditions as well as problems associated with calving that include muscle and back injuries. Cows and sheep are also susceptible to foot abscesses (easily detected) that may need to be drained or pared. This will speed recovery and get them back into production as soon as possible with lower vet bills and less pain and discomfort to the animal.
Many of the past problems with thermal imaging were simply caused by untrained vets and techs using poor techniques with inferior equipment. Additionally, misinterpretations can be caused by different types and thicknesses of fur, moisture in fur and heating or cooling sources in exam area such as sunlight, heating/cooling vents and wind (if outdoors). It cannot be overemphasized that the final interpretation of images should be done by a veterinarian trained in the techniques of thermal imaging.