Authors
Uusitupa T, Laakso I, Ilvonen S, Nikoskinen K. SAR variation study from 300 to 5000 MHz for 15 voxel models including different postures. Phys Med Biol. Jan 28, 2010. 55(4):1157-1176. Ahead of print.

Background
The most relevant dosimetric quantity for electromagnetic fields (EMF) in radiofrequency and microwave ranges is specific absorption rate (SAR). The International Commission on Non-Ionizing Radiation Protection (ICNIRP) defined basic restrictions (limits) for this quantity based on established health effects. Because SAR is not a directly measurable quantity, reference levels (in terms of field strength or power density) are used to provide a practical way to assess exposure. SAR depends on exposure conditions as well as on body size and anatomy and can be computed by the finite-difference time-domain (FDTD) method.

Objective
The objective of the study was to measure SAR in 15 voxel models with 720 simulations using the FDTD method.

Methods
In this study on SAR, 720 free-space plane-wave simulations were performed in the frequency range 300 MHz – 5 GHz. Different incoming directions and polarizations were applied. Fifteen human body models (homogeneous and heterogeneous models of males and females of different weights and various postures) were used.

Results
Detailed results on whole-body SAR and peak 10 g SAR are reported. Variations of SAR on the dB scale are presented as diagrams for different frequencies, polarizations of the electric field, incoming directions, model phantoms and postures.  The results make it possible to determine directly if a SAR value is below the ICNIRP limit at the reference level of exposure.

Interpretation and Conclusion
The data from this study can be used for various purposes, such as to adjust formulas, to extract correction factors and uncertainty estimates for SAR assessment. The results of this research suggest that exposure within the ICNIRP reference levels (especially at frequencies around 2-5 GHz) may result in SAR greater than the basic restriction.


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