Department of Bioengineering, University of Pennsylvania.
Sixth Michealson Research Conference, Cloudcroft NM, Aug. 1999.
Thermal models are a potentially very useful, but underused, tool for assessing thermal hazards of RF exposure. I have recently described one such model and its application for RF safety, Pennes' bioheat equation. I consider here a second model, the Hardy-Stolwijk model for human thermoregulation, as described in Stolwijk's 1977 article in the Handbook of Physiology. The Pennes' model is represented by a partial differential equation that considers heat conduction and convective cooling by blood. It describes heat transport due to these mechanisms, in a local region of tissue. The Hardy-Stolwijk model, by contrast, represents the body by 25 compartments which are assumed to have uniform temperature, and models the heat flows among them. Unlike the Pennes model, the Hardy-Stolwijk model includes physiological thermoregulatory mechanisms. Thus the two models are complementary: the Pennes model is well suited for examining heat flow within a local region of tissue, while the Hardy-Stolwijk model is useful for examining responses to heating that occurs over larger regions of the body. I review recent studies that help validate these models for RF exposure, and the implications of these models for setting RF exposure standards.