Thermography measures the infrared radiation (heat) which is constantly radiating (emitting) away from the surface of the human skin. Skin as an organ breathes, exchanges gases with the environment, cools us as well as keeps us warm by letting heat out or keeping it in by controlling the amount of circulation, or blood flow, in the skin. This automatic regulation is done without conscious thought and is controlled by the autonomic nervous system via the sympathetics. The whole process is called thermoregulation.
The procedure is based on the principle that chemical and blood vessel activity in both pre-cancerous tissue and the area surrounding a developing breast cancer is almost always higher than in the normal breast. Since pre-cancerous and cancerous masses are highly metabolic tissues, they need an abundant supply of nutrients to maintain their growth. In order to do this they increase circulation to their cells by sending out chemicals to keep existing blood vessels open, recruit dormant vessels, and create new ones (neo-angiogenesis). This process results in an increase in regional surface temperatures of the breast.