Dielectric Permittivity and Electrical Conductivity of Fluid Saturated Bone

The dielectric permittivity and electrical conductivity of freshly excised and formalin fixed samples of rat femoral bone were determined over a frequency range of 10 Hz-100 MHz. Impedance measurements were performed in the frequency domain using a vector impedance meter and an impedance analyzer. The results of these measurements show that the conductivity of fixed and fresh bone is nearly independent of frequency below 100 kHz, with the conductivity of fresh bone being two to three times greater than that of the fixed sample. At higher frequencies, the conductivity increases as a power function of frequency. The permittivity of bone reaches very high values at low frequencies, but decreases rapidly with increasing frequencies and approaches a limiting value of about ten. This high-frequency limit is consistent with the water content of the tissue, and with the permittivity of the anhydrous matrix. It is suggested that the olarizability observed at audio and radiowave frequencies is in part sssociated with the collagen phase, although other interfacial polarization effects can also be present.