Foster Kenneth R, Ziskin Marvin C, Balzano Quirino
*Department of Bioengineering University of Pennsylvania, Philadelphia, PA; †Temple University Medical School, Philadelphia, PA; ‡Department of Electrical and Computer Engineering, University of Maryland, College Park, MD.
Health Phys. 2016 Dec;111(6):528-541. doi: 10.1097/HP.0000000000000571.
This is a review/modeling study of heating of tissue by microwave energy in the frequency range from 3 GHz through the millimeter frequency range (30-300 GHz). The literature was reviewed to identify studies that reported RF-induced increases in skin temperature. A simple thermal model, based on a simplified form of Pennes' bioheat equation (BHTE), was developed, using parameter values taken from the literature with no further adjustment. The predictions of the model were in excellent agreement with available data. A parametric analysis of the model shows that there are two heating regimes with different dominant mechanisms of heat transfer. For small irradiated areas (less than about 0.5-1 cm in radius) the temperature increase at the skin surface is chiefly limited by conduction of heat into deeper tissue layers, while for larger irradiated areas, the steady-state temperature increase is limited by convective cooling by blood perfusion. The results support the use of this simple thermal model to aid in the development and evaluation of RF safety limits at frequencies above 3 GHz and for millimeter waves, particularly when the irradiated area of skin is small. However, very limited thermal response data are available, particularly for exposures lasting more than a few minutes to areas of skin larger than 1-2 cm in diameter. The paper concludes with comments about possible uses and limitations of thermal modeling for setting exposure limits in the considered frequency range.
这是一项关于在3吉赫兹至毫米波频率范围（30 - 300吉赫兹）内微波能量对组织加热的综述/建模研究。对文献进行了综述，以确定报告射频引起皮肤温度升高的研究。基于Pennes生物热方程（BHTE）的简化形式开发了一个简单的热模型，使用从文献中获取的参数值且未作进一步调整。该模型的预测与现有数据高度吻合。对该模型的参数分析表明，存在两种具有不同主导传热机制的加热模式。对于小照射面积（半径小于约0.5 - 1厘米），皮肤表面的温度升高主要受热量传导至更深组织层的限制，而对于较大照射面积，稳态温度升高受血液灌注对流冷却的限制。结果支持使用这个简单的热模型来辅助制定3吉赫兹以上频率和毫米波的射频安全限值，特别是当皮肤照射面积较小时。然而，可用的热响应数据非常有限，尤其是对于持续超过几分钟且照射面积大于直径1 - 2厘米的皮肤区域。本文最后对在所考虑的频率范围内用于设定暴露限值的热建模的可能用途和局限性进行了评论。
