A medical technique that makes use of the infrared radiation from the human skin to detect an area of elevated skin temperature that could be associated with an underlying cancer. The heat radiated from the body varies according to the local blood flow, thus an area of poor circulation produces less radiation. A tumour, on the other hand, has an abnormally increased blood supply and is revealed on the thermogram (or thermograph) as a ‘hot spot’. The technique is used particularly in mammography, the examination of the infrared radiation emitted by human breasts in order to detect breast cancer.