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Search for phosphenes induced by amplitude modulated radiofrequency electro-magnetic fields

寻找由调幅射频电磁场引起的光幻视

基本信息

批准号：
12831006
负责人：
TAKI Masao
金额：
$ 2.62万
依托单位：
Tokyo Metropolitan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

It is established that phosphene is perceived by induced current near retina at low frequencies, most sensitively at 20 Hz. Nonlinear characteristics of electric constant of tissue could demodulate radio frequency electromagnetic fields in tissue amplitude modulated at low frequency. Experimental studies and theoretical dosimetry were done based on the hypothesis that modulated field could cause sensations like phosphenes. The results are summarized as follows:(a) Human head was exposed to 900 MHz field amplitude modulated at 20 Hz at up to 30 W/kg. The exposure level was estimated by numerical dosimetry by means of finite-difference time-domain method with anatomically based head model. The phosphene was not perceived in this condition.(b) A lower frequency field of 13.56 MHz was selected in consideration of the dielectric dispersion of molecules near cell membrane. An exposure setup was make for the experiment. Numerical dosimetry at this frequency was investigated to estimate the exposure level.(c) Volunteer study at this frequency was made. The induced current at 13.56 MHz was 2.4 A/m^2, and the specific absorption rate was estimated about 6 W/kg. The phosphene was not perceived for this condition, however.(d) A dosimetry consideration of head and eyeball was made to identify the detailed field and current distributions near retina. Membrane structure was taken into account. The dependence of membrane voltage on frequency and electric constants was investigated in consideration of the membrane structure of retinal tissue. The result suggested that high frequency field does not cause sufficient voltage changes in retinal cells, which was a possible explanation of the absence of phosphene sensation.

在低频率下，视网膜附近的感应电流可以感知到光幻视，在20hz时最敏感。组织电常数的非线性特性可以解调低频振幅调制的组织中的射频电磁场。实验研究和理论剂量学是基于假设，即调制场可以引起像光幻视的感觉。结果总结如下：(a)人体头部暴露于以20 Hz调制的900 MHz场振幅，最高达30 W/kg。采用基于解剖的头部模型，采用时域有限差分数值剂量法估计暴露水平。在这种情况下，不能感知到光幻视。(b)考虑到分子在细胞膜附近的介电色散，选择较低的频率场13.56 MHz。为实验制作了一个曝光装置。研究了该频率下的数值剂量学，以估计暴露水平。(c)按照这个频率进行了自愿研究。在13.56 MHz下，感应电流为2.4 A/m^2，比吸收率约为6 W/kg。然而，在这种情况下，不存在光幻视。(d)对头部和眼球进行剂量学研究，以确定视网膜附近的详细视场和电流分布。考虑了膜结构。考虑视网膜组织的膜结构，研究了膜电压对频率和电常数的依赖关系。结果表明，高频场没有引起视网膜细胞足够的电压变化，这可能是磷光感缺失的一个解释。