INTRODUCTION
The first recorded use of thermobiological diagnostics can be found in the writings of Hippocrates around 480 B.C. [1]. A mud slurry spread over the patient was observed for areas that would dry first and was thought to indicate underlying organ pathology. Since this time, continued research and clinical observations proved that certain temperatures related to the human body were indeed indicative of normal and abnormal physiologic processes. In the 1950's, military research into infrared monitoring systems for night time troop movements ushered in a new era in thermal diagnostics. The first use of diagnostic thermography came in 1957 when R. Lawson discovered that the skin temperature over a cancer in the breast was higher than that of normal tissue [2].
The Department of Health Education and Welfare released a position paper in 1972 in which the director, Thomas Tiernery, wrote, "The medical consultants indicate that thermography, in its present state of development, is beyond the experimental state as a diagnostic procedure in the following 4 areas: (1) Pathology of the female breast. (2)......". On January 29, 1982, the Food and Drug Administration published its approval and classification of thermography as an adjunctive diagnostic screening procedure for the detection of breast cancer. Since the late 1970's, numerous medical centers and independent clinics have used thermography for a variety of diagnostic purposes.

FUNDAMENTALS OF INFRARED IMAGING
Physics -- All objects with a temperature above absolute zero (-273 K) emit infrared radiation from their surface. The Stefan-Boltzmann Law defines the relation between radiated energy and temperature by stating that the total radiation emitted by an object is directly proportional to the object's area and emissivity and the fourth power of its absolute temperature. Since the emissivity of human skin is extremely high (within 1% of that of a black body), measurements of infrared radiation emitted by the skin can be converted directly into accurate temperature values.

Equipment Considerations -- Infrared rays are found in the electromagnetic spectrum within the wavelengths of 0.75 micron - 1mm. Human skin emits infrared radiation mainly in the 2 - 20 micron wavelength range, with an average peak at 9-10 microns [3]. State-of-the-art infrared radiation detection systems utilize ultra-sensitive infrared cameras and sophisticated computers to detect, analyze, and produce high-resolution diagnostic images of these infrared emissions. The problems encountered with first generation infrared camera systems such as improper detector sensitivity (low-band), thermal drift, calibration, analog interface, etc. have been solved for almost two decades.

Laboratory Considerations -- Thermographic examinations must be performed in a controlled environment. The primary reason for this is the nature of human physiology. Changes from a different external (non-clinical controlled room) environment, clothing, etc. produce thermal artifacts. Refraining from sun exposure, stimulation or treatment of the breasts, and cosmetics and lotions before the exam, along with 15 minutes of nude acclimation in a florescent lit, draft and sunlight-free, temperature and humidity-controlled room maintained between 18-23 degree C, and kept to within 1 degree C of change during the examination, is necessary to produce a physiologically neutral image free from artifact.