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.

A simple far-infrared laser interferometer for measuring electron densities in reactive low-temperature plasmas Rev.Silver halide (AgCl x Brl _ x) infrared fibers were incorporated in a simple radiometer. Using this system we performed noncontact temperature measurements in the range 25-50 .c. Good

This paper presents a survey of current work at Tel Aviv University on properties and applications of silver halide infrared transmitting fibers. Various infrared spectral features of core-only fibers, extruded from pure mixed halide crystals of composition AgClBr1(O < x < 1), are presented and discussed. In the best fibers, total loss is as low as 0.15 dB per meter at a wavelength of 10.6 jim. The fibers can be repetitively bent on a 5 cm radius without degrading the transmission, up to thousands of bends. Fibers with a smooth core-clad structure have also been fabricated, but the optical losses are still relatively high. Novel applications of these fibers in spectrophotometry and radiometry are described.

Theoretical calculations are presented for the performance of a fiber-optic radiometer which makes use of infrared transmitting fibers to measure low temperatures (near room temperature). We calculate the radiometer spatial resolution, the dependence of the radiometer signal on the surface temperature, and the minimum resolvable temperature difference (MRDeltaAT) of the radiometer. The performance of the fiber-optic radiometer is compared with a conventional optical (thin lens) radiometer.

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