James Watt School of Engineering, University of Glasgow, University Avenue, Glasgow, G12 8QQ, Scotland, UK.
School of Electronic Engineering and Computer Science, Queen Mary University of London, Mile End Road, London, E1 4NS, England, UK.
Sci Rep. 2022 Mar 19;12(1):4755. doi: 10.1038/s41598-022-08662-7.
The IEEE and ICNIRP had specified a maximum permissible exposure for instantaneous peak electric field of 100 kV/m. However, no rationale was given for this limit. A novel exposure system was designed through a detailed process of analytical analysis, numerical modelling and prototype testing. The system consists of a cylindrical re-entrant resonant cavity that can achieve an electric field strength of more than 100 kV/m with an input power of 200 W. The working of the system was evaluated in simulation and experiment in terms of scattering parameters, electric field distributions and specific absorption rate. The system was then used to carry out in-vitro exposures of a human lymphoid cell line (GG0257) to a 1195 MHz signal at 53 dBm peak power and a pulse width of 550 ns at a range of interpulse intervals to identify heating-induced changes in cell viability. The proposed system offers high Q value of 5920 in unloaded condition which was reduced to 57 when loaded with 12 ml of cell culture but still offering 67 kV/m of the field intensity. Using the system for the exposure of GG0257 cells lasting 18 min, interpulse intervals of 11 μs or less caused a reduction in the number of viable cells and a corresponding increase in necrotic cells. For a shorter exposure duration of 6 min, the reduction in cell viability was seen at interpulse intervals of 5.5 μs or less. The designed exposure system is well capable of handling high intensity electric fields. Temperature measurements with a fibre optic probe and temperature sensitive labels showed that changes in viability were associated with temperature increases above 46 °C. This novel exposure system is an efficient means to investigate the possible relationship between peak field intensity and biological effects to provide a rationale behind the maximum exposure limit of 100 kV/m.
IEEE 和 ICNIRP 规定了瞬时峰值电场的最大允许暴露量为 100 kV/m。然而，并没有给出这个限制的理由。通过详细的分析、数值建模和原型测试过程，设计了一种新型的暴露系统。该系统由一个圆柱形的凹进谐振腔组成，在 200 W 的输入功率下可以达到超过 100 kV/m 的电场强度。通过散射参数、电场分布和比吸收率对系统的工作进行了模拟和实验评估。然后，该系统用于对人类淋巴母细胞系（GG0257）进行体外暴露，暴露频率为 1195 MHz，峰值功率为 53 dBm，脉冲宽度为 550 ns，脉冲间隔范围为识别热诱导的细胞活力变化。该系统在空载条件下具有 5920 的高 Q 值，当加载 12 毫升细胞培养液时，Q 值降低到 57，但仍能提供 67 kV/m 的场强。使用该系统对 GG0257 细胞进行 18 分钟的暴露，脉冲间隔小于 11 μs 会导致活细胞数量减少和坏死细胞数量增加。对于较短的 6 分钟暴露时间，脉冲间隔小于 5.5 μs 会导致细胞活力下降。设计的暴露系统完全能够处理高强度电场。使用光纤探头和温度敏感标签进行的温度测量表明，活度的变化与超过 46°C 的温度升高有关。这种新型暴露系统是一种有效的方法，可以研究峰值场强与生物效应之间的可能关系，为 100 kV/m 的最大暴露限制提供依据。
