Physiology of Thermal Signals
William Herschel first recognized heat emitted in the infrared (IR) wave spectrum in the 1800s. Medical infrared, popularly known as IR-thermography has utilized this heat signature since the 1960s to measure and map skin temperatures. Our understanding of the regulation of skin blood flow, heat transfers through the tissue layers, and skin temperatures has radically changed during these past 40 years, allowing us to better interpret and evaluate these thermographic measurements. During this same period of time, improved camera sensitivity coupled with advances in focal plan array technology and new developments in computerized systems with assisted image analysis have improved the quality of the noncontact, noninvasive thermal map or thermogram [1-3]. In a recent electronic literature search in Medline using the keywords “thermography” and “thermogram” more than 5000 hits were found . In 2003 alone, there were 494 medical references, 188 basic science, 148 applied science (14 combined with Laser Doppler and
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28 combined with ultrasound research), and 47 in biology including veterinary medicine . Further databases and references for medical thermography since 1987 are available .