Hisashi Hirata

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 babys head.

Development state of multifrequency microwave radiometer system for noninvasive measurement of infant's deep brain temperatures

Hypothermia is proposed as a treatment for hypoxia-ischemia in newborn infants who suffer serious cerebral injury or die, if they are brought back early. In this treatment the deep brain temperature monitoring which is noninvasive and continuous is required. Multifrequency microwave radiometry (MWR) is one of the promising candidates for that purpose, and we have been developing a five-band microwave radiometer system and appropriate data processing methods. This paper is to describe the current status of a newly designed MWR system which operates in a normal room with various electromagnetic background noise. Temperature resolutions of the five receivers were obtained by a calibration experiment using a temperature-controlled water-bath. The results of a temperature retrieval simulation experiment is also presented.

Multi-frequency Microwave Radiometer System for Measuring Deep Brain Temperature in New Born Infants

Hypothermic brain treatment for newborn babies are currently hindered by the lack of appropriate techniques for continuous and non-invasive measurement of deep brain temperature. Microwave radiometry (MWR) is one of the promising methods that is completely passive and inherently safe. Five-band microwave radiometer system and its feasibility were reported with a confidence interval level of the temperature estimation of about 1.6 °C at 5 cm depth from the surface. This result was not good enough for clinical application because clinical requirement is less than 1 °C for both accuracy and stability. This paper describes the improved result of temperature resolutions of the five radiometer receivers, and shows the new confidence interval obtained form temperature measurement experiment using an agar phantom based on a water-bath. Temperature resolutions were 0.103, 0.129, 0.138, 0.105 and 0.111 °C for 1.2, 1.65, 2.3, 3.0 and 3.6 GHz receiver, respectively, and new confidence interval was 0.51 °C at 5 cm from surface. We believe that the system takes a step closer to the clinical hypothermic treatment.

P4-11 Effects of odor on event-related potential (P300) and pleasantness

By contrast, in Control, Jaw Movement, and Finger Tapping, they were almost identical among sessions or significantly shorter in Pre than in Post 2 or Post 3. Conclusions: Mastication influences cognitive processing time as reflected by RT and the latency of ERP waveforms. Significance: This is the first study investigating the effect of mastication on the central nervous system using event-related potentials.

23. Event-related potentials related to memory recall, comparison and judgment of the motion direction

the R–R conditions, oxygenated hemoglobin concentration (OxyHb) started to increase approximately 120 s after the task onset, and the increase was larger in the F–F condition than in the R– R condition. The difference was considered to reflect the active process to inhibit responses to the rare non-targets in the F–F condition where the subjects were required to respond semi-automatically to most stimuli. In the F–R and the R–F conditions, Oxy-Hb increased soon after the target probabilities were changed. The increases were assumed to reflect prefrontal cortex activation by shifting of motor response strategy according to target probabilities.