Postmortem changes of the dielectric properties of bovine brain tissues at low radiofrequencies.

The dielectric properties of the bovine brain grey and white matter in the frequency range from 20 kHz to 100 MHz were measured at different times following animal death. Changes in the dielectric parameters versus time are interpreted in terms of the reduction of the cell volume fraction that results from either cell disintegration or cell size reduction. Good agreement between the computer fitted parameters and the values calculated from the Maxwell-Wagner model of the static dielectric constants was found. At frequencies above 1 MHz the changes of the dielectric properties are less pronounced, confirming earlier observations made by other investigators for different species.