国际非电离辐射防护委员会(ICNIRP)参考水平下,暴露于平面波电磁场(10兆赫兹 - 1吉赫兹)的儿童体温升高模拟。
Simulation of the temperature elevation in children exposed to plane wave electromagnetic fields (10 MHz-1 GHz) at the ICNIRP reference level.
作者信息
Niedermayr Florian, Leitgeb Norbert, Siegl Werner
机构信息
Institute of Health Care Engineering, Graz University of Technology, Austria.
出版信息
Biomed Tech (Berl). 2012 May 31;57(3):193-200. doi: 10.1515/bmt-2011-0117.
Because of a lack of thermal models, to date, limitation of exposure to an electromagnetic field (EMF) has been based on restricting intracorporal specific absorption rates. To allow convenient compliance checks, reference field values have been defined. If they are met, compliance with basic restrictions is assumed. This article demonstrates that this assumption is not valid in every case. It has therefore been investigated as to whether the biological goal of limiting tissue heating is still met, in particular with regard to children. The thermal solver applied is based on the bioheat equation, with implemented additional improvements that allow consideration of blood flow and metabolic rate as a function of local tissue temperature rise and, in addition, adapt the blood temperature relative to the absorbed power. As a further improvement, heat exchange at the tissue/air boundary has been modeled, with radiation, convection, and sweating considered as well. The mathematical equations describing these additional thermoregulatory mechanisms were taken from the literature and unified in the thermoregulatory model used for this study. For the investigated case of plane wave exposure, the results confirm the violation of the basic restrictions in five of the six models when exposed to reference EMF levels. However, using thermal modeling, it was possible to demonstrate that heating remained within the biological tolerances. In particular, temperature elevation of the body core temperature remained <0.014°C and the local peak temperature did not exceed 1°C.
由于缺乏热模型,迄今为止,对电磁场(EMF)暴露的限制一直基于限制体内比吸收率。为了便于进行合规检查,已定义了参考场值。如果满足这些值,则假定符合基本限制。本文表明,这种假设并非在所有情况下都有效。因此,已对是否仍能实现限制组织发热的生物学目标进行了研究,特别是针对儿童。所应用的热求解器基于生物热方程,并实施了额外的改进,允许将血流和代谢率视为局部组织温度升高的函数,此外,还根据吸收功率调整血液温度。作为进一步的改进,对组织/空气边界处的热交换进行了建模,同时考虑了辐射、对流和出汗。描述这些额外体温调节机制的数学方程取自文献,并统一在本研究使用的体温调节模型中。对于平面波暴露的研究案例,结果证实,在暴露于参考EMF水平时,六个模型中有五个违反了基本限制。然而,通过热建模,可以证明加热仍在生物学耐受范围内。特别是,体核温度的升高保持在<0.014°C,局部峰值温度未超过1°C。