Absorption Characteristics of Multilayered Sphere Models Exposed to UHF/Microwave Radiation

The interaction of electromagnetic plane waves with multilayered spherical models composed of lossy dielectric media that represent different biological tissues found in human and animal heads is examined in the frequency range 0.1 to 10 GHz. The model ranges in size from 2 to 12.5 cms outer radius and consists of a core of brain-like material surrounded by five outer layers of CSF, bone, fat and skin-dura tissues. The absorption properties of the model have been analyzed throughout this range of size and frequency. The distribution of internally deposited energy has also been investigated in detail for three basic spheres of 3.3, 6 and 10 cms radii, with emphasis on the creation of localized regions of strong heating (hot-spots). Based on these results, some generalized conclusions are presented on the interaction of microwaves with different sized biological objects.