Five-band microwave radiometer system for non-invasive measurement of brain temperature in new-born infants: system calibration and its feasibility

Recent simulation studies have shown that a technique of multi-frequency microwave radiometry is feasible for non-invasive measurement of deep brain temperatures in the new-born infants. A five-band microwave radiometer system has been developed, and its operation in a normal electromagnetic environment is checked. Five receivers operating with a waveguide antenna and at center frequencies of 1.2, 1.65, 2.3, 3.0 and 3.6 GHz (0.4 GHz bandwidth) are calibrated using a temperature-controlled water-bath. Temperature resolutions obtained for each receiver are 0.183, 0.273, 0.148, 0.108 and 0.118 K, respectively. A temperature retrieval simulation based on these resolutions and the previously proposed algorithm shows that the confidence interval, as produced by thermal noise, is 0.62 K for the retrieved central brain temperature. If the conductivity of brain is estimated wrong by 10 %, this will result in an error of 0.3 - 0.4 K. The result of this work is encouraging for realization of radiometric measurement of temperature profile in a baby´s head.