Plane-wave model for electromagnetic power absorption in biological tissues

The phenomenon of electromagnetic power absorption in biological tissues has recently become of increased scientific and public interest, particularly in the areas of cellular communication and hyperthermia systems. Electromagnetic power absorption in biological tissues is a well-known phenomenon. Its evaluation requires, in general, a solution of the three-dimensional frequency-dependent wave equation in complex configurations, which may necessitate quite massive analytical and numerical efforts. Herein, we focus on an elementary plane-wave model. The model establishes a tight estimate on the optimal (maximal/minimal) power absorption in realistic microwave configurations, in particular, cellular communications safety assessments. Furthermore, the absorption efficiency as well as the source impedance are obtained via explicit closed-form expressions, leading to an explicit maximal power absorption criterion for highly lossy tissues. The results depend continuously and explicitly,on the physical parameters of biological tissues as well as on the plane-wave incidence angle and excitation source location. They are shown to be closely related to electromagnetic specific absorption rate estimations in biological tissues. In view of the well-known analogy between plane waves and rectangular waveguide modes, our results can be applied to optimization schemes of microwave heating and waveguide based therapeutic hyperthermia systems. (C) 2003 American Institute of Physics.