Effective complex conductivity of skeletal muscle in the radio-frequency range

This work deals with the dielectric properties of biological tissues comprising tubular cells, such as skeletal muscle. This issue is of significance to many applications for noninvasive diagnosis and treatment, such as electrical impedance tomography, body composition, dialysis, radio-frequency hyperthermia and ablation. The dielectric properties of tissues vary as a function of frequency. Experiments show indeed three dispersions, α, β and γ, mainly attributed to different relaxation processes: ionic diffusion, interfacial polarization and dipolar orientation, respectively. The β dispersion, considered herein, takes place in the radio-frequency range and principally arises from the capacitive charging of cell membranes, known as Maxwell-Wagner effect. Different phenomenological relaxation models are available in the literature, as well as equivalent-circuit models, which however pose the problem of parameter identification. In the present work, a micromechanical approach is used, which enables to derive the effective dielectric properties of the tissue from the properties of the constituent phases and to take into account microstructural details.