Laakso Ilkka, Morimoto Ryota, Heinonen Juhani, Jokela Kari, Hirata Akimasa
Department of Electrical Engineering and Automation, Aalto University, Espoo, Finland.
Phys Med Biol. 2017 Aug 9;62(17):6980-6992. doi: 10.1088/1361-6560/aa81fe.
Restrictions on human exposure to electromagnetic waves at frequencies higher than 3-10 GHz are defined in terms of the incident power density to prevent excessive temperature rise in superficial tissue. However, international standards and guidelines differ in their definitions of how the power density is interpreted for brief exposures. This study investigated how the temperature rise was affected by exposure duration at frequencies higher than 6 GHz. Far-field exposure of the human face to pulses shorter than 10 s at frequencies from 6 to 100 GHz was modelled using the finite-difference time-domain method. The bioheat transfer equation was used for thermal modelling. We investigated the effects of frequency, polarization, exposure duration, and depth below the skin surface on the temperature rise. The results indicated limitations in the current human exposure guidelines and showed that radiant exposure, i.e. energy absorption per unit area, can be used to limit temperature rise for pulsed exposure. The data are useful for the development of human exposure guidelines at frequencies higher than 6 GHz.
对人类暴露于频率高于3 - 10吉赫兹的电磁波的限制是根据入射功率密度来定义的，以防止表层组织出现过度的温度升高。然而，国际标准和指南在如何解释短时间暴露时的功率密度方面存在差异。本研究调查了在高于6吉赫兹的频率下，暴露持续时间如何影响温度升高。使用时域有限差分法对人类面部在6至100吉赫兹频率下暴露于短于10秒的脉冲进行了远场建模。生物热传递方程用于热建模。我们研究了频率、极化、暴露持续时间以及皮肤表面以下深度对温度升高的影响。结果表明了当前人类暴露指南存在局限性，并表明辐射暴露，即单位面积的能量吸收，可用于限制脉冲暴露时的温度升高。这些数据对于制定高于6吉赫兹频率下的人类暴露指南很有用。
