The information which each provides is different. Thermography involves getting an image of the breast by using infrared thermal technology. Sensitive infrared cameras accompanied with a sophisticated computer program can detect and reproduce temperature variations which may signal the very earliest signs of breast cancer or a pre-cancerous state. The key to thermography is unusual blood vessel activity. The blood vessels feeding malignant tumours are different from other blood vessels in that there is no smooth muscle in them.
Normal vessels constrict in response to cold.
Vessels feeding tumours do not constrict. This lack of constriction shows up on the screen in the form of a different image from other blood vessel activity. Detecting unusual heat patterns in the body is a diagnostic technique that goes back to the days of Hippocrates. By putting mud all over the body and observing abnormal rates of drying, they learned that abnormal heat could be a sign of tumour activity. Like mammography and ultrasound, the technology behind thermography was originally developed for military use in the United States.