2001 Fiscal Year Final Research Report Summary
Search for phosphenes induced by amplitude modulated radiofrequency electro-magnetic fields
| Project/Area Number |
12831006
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Institution | Tokyo Metropolitan University |
|---|
Principal Investigator |
TAKI Masao Tokyo Metropolitan University, Professor, 工学研究科, 教授 (60145670)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
WATANABE Soichi Communications Research Laboratory, Senior Researcher, 主任研究官 (30358957)
TANAKA Toshiyuki Tokyo Metropolitan University, Associate Professor, 工学研究科, 助教授 (10254153)
|
|---|
| Project Period (FY) |
2000 – 2001
|
| Keywords | electromagnetic field / radiofrequency / biological effect / nonthermal / modulation / phosphene |
|---|
| Research Abstract |
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.
|
