Derivation of complex resistivity values from MFEIT images formed with reactive references

The electrical response of tissue conveys information about the nature of tissue at a cellular level. Several methods have been described in the literature to determine the complex resistivity of tissue from pixels of multi-frequency electrical impedance tomography (MFEIT) images. These methods are limited in use by the requirement of a homogeneous, resistive reference or by the assumption that the tissue is characterised by a single Cole dispersion. An alternative method of image formation, referred to as "phase magnitude imaging", is presented in this paper. Absolute and phase magnitude images were formed from voltage profiles generated from a FDM simulation of a liver sample immersed in electrolyte. The complex resistivity values derived from these images agreed precisely, but Cole parameters calculated from the values differed by up to 17% from the true values due to the finite resolution and geometrical dependence of the reconstruction algorithm. These results indicate that the phase magnitude imaging enables the complex resistivity of tissue to be derived from MFEIT image data using inhomogeneous and reactive references, independent of the tissue model.