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Accurate FDTD simulation of biological tissues for bioelectromagnetic applications

For practical bio-electromagnetic applications, such as the interaction of electromagnetic fields with the human head and body, accurate simulation of biological tissues is a key factor for reliable results. The characteristics of biological tissues are frequency dependent and thus called dispersive materials. For accurate FDTD simulation of biological tissues, a numerical technique is proposed to derive the Debye coefficients from the measured frequency-dependent permittivity of different biological tissues, and then a scattered field FDTD formulation is developed for such dispersive media characterized by multi-term Debye expressions. The proposed scattered field FDTD formulation is valid for three dimensional analysis of practical EM problems involving combination of dispersive and non-dispersive materials. The developed procedure has been verified for different types of biological tissues over a very wide band of frequency (from 30 Hz to 20 GHz). The reflection coefficients of a semi-infinite dispersive medium using one, two, and three-term Debye expressions are computed and compared favorably with the corresponding analytical solution. Hence, the accuracy and stability of modeling multi-term Debye dispersive materials using the proposed scattered FDTD formulation is assessed.