1998 Volume 118 Issue 2 Pages 188-194
The final purpose of our study is the non-invasive measurement of the brain temperature change by head capacitance measurements. Establishment of this technique might be useful for the diagnosis of brain death, since it is reported that in the brain death the brain temperature is influenced by the surrounding temperature change.
It is necessary for the establishment of this technique to acquire knowledge of the specific dielectric constant - temperature characteristics of the human head tissue. For this purpose, we examined the specific dielectric constant-temperature characteristics of the hog brain and skull which were obtained immediately after the death. As the experiment result, we estimated the specific dielectric constant to be about 1300 for the brain and around 3 for the skull in living condition, and its temperature coefficient about 1.84%/°C for the brain and around 0.23%/°C for the skull.
Applying those estimated values to the human head, it was demonstrated to be possible to detect the change in human brain temperature from 37°C to 36°C by measuring the capacitance of the human head model consisting of only the brain and the skull across a pair of measurement electrodes of 1 cm2 area, under the condition of voltage in 20V with 500 kHz.