Kawai H, Nagaoka T, Watanabe S, Saito K, Takahashi M, Ito K. Computational dosimetry in embryos exposed to electromagnetic plane waves over the frequency range of 10 MHz-1.5 GHz. Phys. Med. Biol. Dec 10, 2009 Ahead of print.

Until now, most radiofrequency electromagnetic field (RF-EMF) dosimetry studies on pregnant women models have been conducted on models of mid to late pregnancy. In the available studies of dosimetry in embryos , electromagnetic propagating directions are limited. Temperature elevations due to electromagnetic exposures of embryo and fetus have not yet been ascertained.

The objective of this study was to provide data on SARs in embryos exposed to vertically and horizontally polarized electromagnetic plane waves at 4 different propagation directions, for future thermal calculations.

In early pregnancy, the maternal abdomen is of similar size to that of a non-pregnant woman, amniotic fluid is only slightly developed, the position of placenta is unknown and the movement of embryos in the uterus is scarce. Based on these characteristics, numerical models of four -and eight-week pregnant woman have been developed by setting simple embryos into the non-pregnant female model with height and weight of the average Japanese female with 2 mm spatial resolution. Reference mass and length of embryos were according to average Japanese values. The embryos were considered a homogenous tissue. Dielectric properties of the embryos were adjusted to account for their relatively high water content. Exposure to plane waves over the frequency range from 10 MHz to 1.5 GHz was considered. The finite-difference time-domain method was used for numerical calculations.

Results, interpretation and conclusion
When the incident power density was at the ICNIRP reference level for general public, the maximum embryo-averaged SAR for exposure to plane waves was lower than 0.08 W/kg. The average SAR of the 4 week embryo was almost the same as that of the 8 week embryo. In the near future, the SARs calculated in this study will be used for temperature calculations in the embryo.

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