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首页> 外文期刊>Physics in medicine and biology. >Children and adults exposed to low-frequency magnetic fields at the ICNIRP reference levels: Theoretical assessment of the induced electric fields
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Children and adults exposed to low-frequency magnetic fields at the ICNIRP reference levels: Theoretical assessment of the induced electric fields

机译：在ICNIRP参考水平下暴露于低频磁场的儿童和成人：感应电场的理论评估

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To avoid potentially adverse health effects, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined reference levels for time varying magnetic fields. Restrictions on the electric fields induced in the human body are provided based on biological response data for peripheral nerve stimulation and the induction of phosphenes. Numerical modeling is commonly used to assess the induced electric fields for various exposure configurations. The objective of this study was to assess the variations of the electric fields induced in children and adults and to compare the exposure at reference levels with the basic restrictions as function of anatomy. We used the scalar potential finite element method to calculate the induced electric fields in six children and two adults when exposed to uniform magnetic fields polarized in three orthogonal directions. We found that the induced electric fields are within the ICNIRP basic restrictions in nearly all cases. In PNS tissues, we found electric fields up to 95% (upper uncertainty limit due to discretization errors, k = 2) of the ICNIRP basic restrictions for exposures at the general public reference levels. For occupational reference levels, we found an over-exposure of maximum 79% (k = 2) in PNS tissues. We further found that the ICNIRP recommendations on spatial averaging in 2×2×2 mm 3 contiguous tissue volumes and removal of peak values by the 99th percentile cause the results to depend strongly on the grid discretization step (i.e. an uncertainty of more than 50% at 2 mm) and the number of distinguished tissues in the anatomical models. The computational results obtained by various research institutes should be robust for different discretization settings and various anatomical models. Therefore, we recommend considering alternative routines for small anatomical structures such as non-contiguous averaging without taking the 99th percentile in future guidelines leading to consistent suppression of peak values amongst different simulation settings and anatomical models. The peak electric fields depend on the local tissue distribution in the various anatomical models, and we could not find a correlation with the size of the anatomy. Therefore, we recommend extending the evaluation using a sufficient set of anatomies including other than standing postures to assess the worst-case exposure setting and correspondence to the basic restrictions.
机译：为避免潜在的不利健康影响，国际非电离辐射防护委员会（ICNIRP）为时变磁场定义了参考水平。基于周围神经刺激和的生物反应数据，提供了对人体感应电场的限制。数值建模通常用于评估各种曝光配置的感应电场。这项研究的目的是评估在儿童和成人中感应的电场的变化，并将参考水平的暴露与基本限制作为解剖功能进行比较。我们使用标量势有限元方法计算了六个孩子和两个成年人在暴露于沿三个正交方向极化的均匀磁场中的感应电场。我们发现，几乎在所有情况下，感应电场都在ICNIRP基本限制之内。在PNS组织中，我们发现电场的ICNIRP基本暴露限制高达95％（由于离散化误差而导致的最大不确定性限制，k = 2），处于普通公众参考水平。对于职业参考水平，我们发现PNS组织中的最大暴露量最大为79％（k = 2）。我们进一步发现，ICNIRP建议在2×2×2 mm 3的连续组织空间中进行空间平均，并去除第99个百分位数的峰值，这导致结果在很大程度上取决于网格离散化步骤（即不确定性超过50％ （在2毫米处）和解剖模型中可分辨的组织数量。各种研究机构获得的计算结果对于不同的离散化设置和各种解剖模型应具有鲁棒性。因此，我们建议考虑使用较小的解剖结构的例程，例如不连续的平均，而在将来的指南中不采用第99个百分位数，从而在不同的模拟设置和解剖模型之间始终抑制峰值。峰值电场取决于各种解剖模型中的局部组织分布，我们无法找到与解剖结构大小的相关性。因此，我们建议使用包括站立姿势以外的足够解剖结构来扩展评估，以评估最坏情况下的暴露设置以及与基本限制的对应关系。

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