In Germany, Marianus Czerny, the professor of physics at Goethe Institute Frankfurt University, laid foundations for the development of thermal sensors. One of his students in the USA, Bowling Barnes, built the first thermal imager based on thermistors in the 1950s. While cooled detector systems give high performance thermal imaging, uncooled cameras have reached a high level of thermal resolution and are more convenient in clinical applications. Following pandemic fever outbreaks, for example severe acute respiratory syndrome and avian flu, the need for fever screening in international travel led to the employment of thermal imaging. The International Organization for Standardization was required to address the issue of minimum standards needed to detect the presence of fever. Thermal imaging has been first used as an outcome measurement in the field of rheumatology. Different dosage of anti-inflammatory compound drugs was objectively compared in clinical trials. At that time, little attention had been given to standardization of procedures.