Resonance Absorption of Microwaves by the Human Skull

Resonance absorption of microwaves by the human skull is examined by making computerized calculations of theoretical models of the skull. The calculated relative absorption versus frequency is plotted and compared for homogeneous and inhomogeneous skull models. At a frequency of maximum power absorption, the spatial distribution of intracranial field intensity (based upon the theoretical model) is also calculated and plotted. Modeling the skull as a multilayered sphere corresponding to skin, fat, bone, dura, cerebrospinal fluid, and the brain (six concentric spheres), each layer having a specific conductivity and dielectric constant expressed as a function of frequency, we have developed a computer program for calculating the relative absorption and internal distribution of electric field intensity at microwave freqeuncies. To cover a range of skull sizes, calculations are made for spheres of radius 7 and 10 cm. At frequencies within the 0.1-3-GHz band, our results show a pronounced difference between the incident energy absorbed by the homogeneous and the inhomogeneous (multilayered) skull models. Of particular interest is a broad relative absorption peak near 2.1 GHz that does not appear for the homogeneous skull model. Since the multilayered sphere represents a closer approach to reality in modeling the human skull at microwave freqeuncies, the leakage from microwave ovens operating at 2.45 GHz may be a greater hazard to human health than is now being recognized. Copyright © 1974 by The Institute of Electrical and Electronics Engineers, Inc.

Duke Scholars

Author William T. Joines Electrical and Computer Engineering