In vivo and in vitro dielectric properties of feline tissues at low radiofrequencies.

The dielectric constant and conductivity of muscle, liver, spleen and kidney of cats in vivo and in situ immediately following the animal's death were measured at frequencies from 10 kHz to 100 MHz. A novel multi-ring capacitive sensor and a computer-controlled automatic network analyser (ANA) were employed. The results were compared with the data available from literature for the same species in the frequency range between 10 and 100 MHz. It was found that at frequencies from 10 to 100 kHz the in vitro dielectric constant for all tissues except spleen was smaller than the in vivo one. In contrast, in the range from 1 to 100 MHz the in vitro dielectric constant was larger than the in vivo one. At intermediate frequencies from 0.1 to 1 MHz both the dielectric constant in vivo and in vitro were the same within the experimental uncertainty. The dielectric constant of the spleen in vivo was quite similar to that in vitro. The in vivo conductivity of all tissues appeared to be higher than in vitro from 10 kHz to 10 MHz, while at frequencies above 10 MHz the two conductivities were within the experimental uncertainty.