Dielectric properties of blood: an investigation of temperature dependence.

We have investigated the temperature dependence of the electrical parameters (permittivity and conductivity) of blood. The measuring system, composed of an impedancemeter (HP 4291 A), an open-ended coaxial line and a temperature controlling set, was designed for dielectric measurement in the frequency range of 1 MHz to 1 GHz. Measurements were performed on ex vivo blood of humans and animals (cow and sheep). The results obtained show the weak sensibility and a change of sign of the temperature coefficient of the relative permittivity (about 0.3% degrees C(-1) at 1 MHz and -0.3% degrees C(-1) at 1 GHz). The conductivity presents a more significant variation (of the order of 1% degrees C(-1) over the whole operating frequency range.