Local thermal spikes in biological systems disposed in a low intensity electromagnetic field

Abstract

Pennes’ equation for bioheat transfer and the heat transfer differential equation are solved for the temperature distribution in a living tissue with spherical inclusions, irradiated by microwave power. It is shown that relative temperature excess in a small inclusion in the tissue in some cases is inversely proportional to its radius and does not depend on the applied power. In pulsing RF fields the effect is amplified proportionally to the ratio of the pulse period to the pulse duration. The local temperature rise significantly outpaces the averaged one and therefore the Watt to Weight SAR limits may be insufficient to estimate the safety of RF radiation and the conventional division of the biological effects of electromagnetic fields on the thermal and non-thermal needs to be revised.