Feasibility of noninvasive measurement of deep brain temperature in newborn infants by multifrequency microwave radiometry

Clinical studies of hypothermal neural rescue therapy for newborn infants w ho have suffered hypoxia-ischaemia are currently hindered by the difficulty in measuring deep brain temperature. This paper addresses: the specific re quirements for this measurement problem, the design of a proposed radiomete r system, a method for retrieving the temperature profile within the cooled head, and an estimation of the precision of the measurement of deep brain temperature using the technique, A five-frequency-band radiometer with a co ntact-type antenna operating within the range 1-4 GHz is proposed to obtain brightness temperatures corresponding to temperature profiles predicted by a realistic thermal model of the cooled baby head. The problems of retriev ing the temperature profile from this set of brightness temperatures, and t he estimation of its precision, are solved using a combination of model fit ting and Monte Carlo techniques. The results of this paper show that the pr oposed technique is feasible, that it is expected to provide a good estimat e of the temperature profile within the cooled baby-head, and that the esti mated precision (2 sigma) of the temperature measured in the deep brain str uctures is better than 0.8 K, depending upon the estimation procedure used.