When environmental and physiological influences are held constant, heat radiation (ie, infrared radiation) from a region of the human body is a function of blood flow to that region. Because of this, tactile estimation of the warmth of an extremity is commonly used to assess vascular sufficiency. When more quantitative and objective measurements are desired, thermocouples or thermistors may be placed on the skin. Though precise, these devices have two disadvantages. First, it is necessary to make direct contact with the part whose temperature is to be measured; and, second, the information obtained refers only to the small point at which the sensing device is located.There are occasions when it would be useful to have a temperature "map" of a whole region of the body obtained simultaneously and without direct contact. In recent years several types of infrared sensing devices have been developed which, though primarily designed for
HOFFMAN L, DiMATTIA A. Clinical Use of the Infrared Thermogram. Arch Intern Med. 1964;113(2):218–224. doi:10.1001/archinte.1964.00280080054011
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