Thermography presents a noninvasive, safe, and cost-effective diagnostic imaging modality (on average, $350 for a whole horse scan and interpretation) that is a valuable complementary tool in equine health care. As with other technologies, we are seeing considerable advancements in thermographic cameras’ resolution and user-friendliness, along with significant decreases in physical size and initial purchase costs. As thermography gains popularity and interest, it is tremendously important that veterinarians, technicians, and horse owners understand the advantages this physiologic imaging tool offers, as well as its limitations.
The first step in understanding what thermography can and can’t do is learning the difference between anatomic and physiologic imaging. Anatomic imaging, which includes radiographs, CT scans, and MRI, reveals to the practitioner a specific affected area. These techniques show one static moment in time of a body part and are not sensitive to metabolic changes in blood flow or nerve conduction. Physiologic imaging is dynamic and sensitive and includes nuclear scintigraphy (bone scan) and infrared thermography. The latter might detect metabolic changes related to active inflammation, blood flow, or nerve conduction. Veterinarians typically follow thermography with anatomic imaging to diagnose the underlying disease process at a specific area of activity or concern.
So how does thermography work? The thermographic camera detects infrared waves on the body surface that are invisible to the human eye and converts them to an image we can see. Consider what happens when you injure yourself: You bang your knee; the area becomes hot, red, and inflamed; and at a cellular level as an immune response, the body releases chemicals such as histamine. Changes in blood flow might directly correlate with inflammation. Thus, at the most basic level, where there is increased circulation there might be inflammation (becoming warmer). The opposite is also true: With chronic disease, scarring, atrophy (muscle wasting/loss), nerve damage, or disuse, areas might become cooler.
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