Bahr A, Bolz T, Hennes C
IMST, Kamp-Lintfort, Germany.
Health Phys. 2007 Jun;92(6):521-30. doi: 10.1097/01.HP.0000251249.00507.ca.
In situ electric fields and current densities are investigated by numerical simulations for exposure to ELF electric and magnetic fields. Computations are based on the finite-difference time-domain method (FDTD). The computational uncertainty is determined by comparison of analytical and numerical results and amounts to a worst-case expanded uncertainty (95% confidence interval) of +/-9.89 dB for both dosimetric quantities (E, J). Detailed investigations based on the Visible Human body model with a resolution of 2 mm show a strong influence of the tissue boundaries on the simulation results, which is caused by the numerical method. For the tissue specific in situ electric field and current density changes in excess of 10 dB are observed when comparing the results with and without evaluation of the dosimetric quantities at tissue boundaries. Moderate sensitivities with respect to tissue boundaries are observed only for low conductivity tissues when evaluating the in situ electric field whereas this behavior is observed for high conductivity tissues when evaluating the current density. For exposure to a 50 Hz magnetic field corresponding to the ICNIRP reference level, the simulated current density for central nervous system (CNS) tissue is in compliance with the ICNIRP guidelines. Exposure to a 50 Hz electric field may exceed the ICNIRP basic restriction for CNS tissue at least in a worst-case scenario (grounded human body, vertical electric field, tissue boundaries included for the evaluation of the current density). The in situ electric field is the more stable dosimetric quantity with respect to changes of the tissue conductivity of the Visible Human body model. The maximum conductivity sensitivity coefficient amounts to +122% for the current density whereas the maximum sensitivity coefficient for the in situ electric field is -20%. For electric field exposure the in situ electric field remains comparable (-6% to -4%), the averaged current density change ranges from -57% to -16% for the tissues under investigation. Magnetic field exposure of a scaled model of a five year old child leads to a decrease of the dosimetric quantities (J: -74% to -45%, E: -42% to -23%) compared to the Visible Human results.
通过数值模拟研究了暴露于极低频电场和磁场时的原位电场和电流密度。计算基于时域有限差分法（FDTD）。通过比较解析结果和数值结果确定计算不确定度，对于两个剂量学量（E，J），最坏情况下的扩展不确定度（95%置信区间）为±9.89 dB。基于分辨率为2 mm的可视人体模型进行的详细研究表明，组织边界对模拟结果有很大影响，这是由数值方法引起的。当比较考虑和不考虑组织边界处剂量学量评估的结果时，观察到特定组织的原位电场和电流密度变化超过10 dB。在评估原位电场时，仅对低电导率组织观察到对组织边界的中等敏感性，而在评估电流密度时，对高电导率组织观察到这种行为。对于暴露于对应于国际非电离辐射防护委员会（ICNIRP）参考水平的50 Hz磁场，中枢神经系统（CNS）组织的模拟电流密度符合ICNIRP指南。暴露于50 Hz电场时，至少在最坏情况下（接地人体、垂直电场、评估电流密度时包括组织边界）可能超过ICNIRP对CNS组织的基本限制。原位电场相对于可视人体模型组织电导率的变化是更稳定的剂量学量。电流密度的最大电导率敏感系数为+122%，而原位电场的最大敏感系数为-20%。对于电场暴露，原位电场保持可比（-6%至-4%），所研究组织的平均电流密度变化范围为-57%至-16%。与可视人体结果相比，对一名五岁儿童的缩放模型进行磁场暴露会导致剂量学量降低（J：-74%至-45%，E：-42%至-23%）。
