Rigorous characterization of resonant hot spot conditions in a stratified tissue model

A unified approach for determining the lossy resonance (hot-spot) conditions in a lossy stratified biological tissue model is proposed. These conditions may lead to a significant enhancement of local electromagnetic power deposition in a single layer as compared to the power dissipated in the background. Rigorous analysis of electromagnetic wave power absorption in a planar stratified tissue model renders a closed-form characterization of six possible asymptotic cases and the associated conditions and bounds on the optimal absorption in the particular layer as a function of its normalized thickness and parameters of the surrounding layers. It is shown that, even very thin and low attenuating layers (sites) of biological tissue, are capable of dissipating a very substantial amount of the incident power, subject to specific lossy resonance conditions. From a dosimetric point of view, the results obtained allow for prediction of naturally occurring spatial resonances in biological tissues on both macroscopic and microscopic scales. On the other hand, they also provide an effective mean for design and synthesis of optimally absorbing materials and tissues in therapeutic applications.