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Since the 1930’s, mean skin temperature has been routinely measured through the use of thermistors, thermocouples, and thermocrons that are often attached to the skin directly.
While useful in their assessment of skin temperature, these techniques are limited due to slow response times, wires causing restriction of the subject, and sensors falling off due to sweat production.
Medical Infrared Thermography
Non-contact infrared thermal imaging, referred to as Medical Infrared Thermography (MIT) for clinical purposes, is a non-radiating technology that enables the detection and location of thermal abnormalities to be identified by increases or decreases in skin surface temperature. Used in a wide variety of medical applications, ranging from surgery, neurology, oncology, orthopedics and dermatology, MIT has a unique ability to enhance diagnostic measurements in a quick and non-invasive way.
As the primary regulator of blood circulation in the skin, the sympathetic nervous system controls the body’s thermal emissions that can be captured by MIT devices. With an emissivity factor of 0.98, the human body is a perfect emitter of infrared radiation at room temperature, allowing thermal-imaging cameras to capture images through the energy produced by human tissue. The energy content of the body’s thermal emission is therefore directly related to the wavelength of the applied radiation.
Characterized by an increase or decrease in the skin temperature (Tsk), thermal changes or abnormalities are recorded by specialized infrared thermal imaging cameras, producing a visual image of the calculated Tsk, otherwise known as a thermogram. This two-dimensional image is produced by specific software that incorporates anatomical and physiological information by image fusion, providing physicians with specific data on the extent of the injury.
MIT in Sports Medicine
In sports medicine, MIT is becoming one of the most popular methods of assessing skin temperature in an effort to identify risk factors and prevent future injuries in training and during competition. Athletes often suffer from overuse injuries, otherwise known as cumulative trauma disorders, which is tissue damage caused by repetitive demand over time.
Overuse injuries, as well as several other pathophysiological injuries, cause inflammation and subsequent increases in skin temperature surrounding the affected region. As a result of this an increase in skin temperature, and disturbances to the normal anatomical symmetry occur.
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MIT is able to detect any disturbances to the normal symmetry, allowing sports medicine professionals to quickly identify risk factors and gage potential treatment responses. In sports medicine, MIT has been useful for the diagnosis of epicondylitis, patellofemoral syndromes, ankle injuries, stress fractures, shin splints, myofascial pain syndromes, shoulder injuries, spinal pain syndromes, foot pain syndromes, and vascular disorders, however its biggest contribution to sports medicine has been its ability to detect posttraumatic pain syndromes of reflex sympathetic dystrophy and relating sympathetic maintained pain syndromes following minimal injury.
Further Development of MIT
In the last few decades a revolutionary development of digital technology has occurred in almost every industry available, and its growing presence in medicine is no different. For thermal imaging devices, improvements in the quality of the camera and post process analysis technology have led to increasing efficiency and a subsequent increase in the use of thermal imaging devices as supplemental diagnostic tools.
Originally recognized by the American Medical Association in 1987 as a feasible diagnostic tool, the heightened use of MIT in medicine was also recently recognized by the American Academy of Medical Infrared Imaging. Various medical thermography groups and associations exist around the world in an effort to ensure the future improvement and development of appropriate and reliable methods for the clinical application of MIT. With an increase in thermal sensitivity, computerized systems using complex statistical data analysis ensure the ability of MIT to produce high-quality results.
Veterinary medicine has successfully utilized MIT to detect locomotion injuries in racehorses and other athletic animals in an effort to monitor health status. While there is limited scientific evidence of the successful application of MIT in human sports medicine, the anatomical and physiological similarities between animals and humans may imply that this technology could assist injury management in athletes as well. Future research in the field of injury prevention and management, and the potential incorporation of MIT technologies in these fields remains crucial.
References and Further Reading