Pulsed Response of Optimally Absorbing Tissue Layers for Hyperthermic Applications

Several thermal therapy modalities make use of electromagnetic waves in order to deliver thermal energy into the treated site, e.g. waveguide applicators, microwave phased arrays, near-infrared lasers. Effective treatment should deliver, in all cases, as much energy as possible to the target, while minimizing losses in other tissues due to attenuation in the propagation path, scattering, diffraction etc. By analyzing a one-dimensional layered model of typical thermal therapy configuration, it is shown how a resonant absorption conditions can be created within the target, leading to significant improvement in the local power deposition. The conditions, parameters and bounds for the optimal (maximal) incident power absorption within the target layer have been found analytically and explicitly versus its normalized thickness. The results are extended to optimization of pulsed field absorption.