Correlation of permittivity and water content during cerebral edema

Correlation between the permittivity of white matter and cerebral edema was studied. A time domain reflectometer was used to measure the permittivity changes of canine cerebral white matter due to edema produced in vitro by osmosis over a frequency range of 100 MHz to 1 GHz. For all frequencies, a strong correlation was found between the water content and the dielectric constant (R approximately 0.86) and loss factor (R approximately 0.82). The results suggest that it may be possible to estimate both the tissue water content as well as the composition of the accumulated edematous fluid.