Hypothermia is a condition which results from prolonged exposure to a cold environment. Rapid and efficient heating is needed to rewarm the patient from 32-35 degrees C to normal body temperature. Hyperthermia in cancer treatment involves heating malignant tumors to 42.5-43.0 degrees C for an extended period (e.g., 30 min) in an attempt to obtain remission. Microwave or radio frequency heating is often used for rewarming in hypothermia or for temperature elevation in hyperthermia treatment. One severe problem with such heating is the accurate measurement and control of temperature in the presence of a strong electromagnetic field. For this purpose, we have developed a fiberoptic radiometer system which is based on a nonmetallic, infrared fiber probe, which can operate either in contact or noncontact mode. In preliminary investigations, the radiometer worked well in a strong microwave or radiofrequency field, with an accuracy of +/- 0.5 degrees C. This fiberoptic thermometer was used to control the surface temperature of objects within +/- 2 degrees C.

Electromagnetic (microwave or radio frequency) field-induced heating is used in industrial, medical, and domestic applications. In most cases, efficient, rapid, and controllable heating is needed. A problem with this heating modality is the difficulty in gaining an accurate measurement of temperature in the presence of a strong electromagnetic field. A simple infrared fiber-radiometer system has been developed for thermometry in the presence of these strong electromagnetic fields. The radiometer was used to measure temperatures in the range 0–70 °C, with an accuracy of ±0.5 °C. The signal obtained varied almost linearly with temperature.

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