Age Effect on Spatial Peak SAR of Dielectric Properties of Head Tissues for Portable Telephones

摘要

In evaluating the electromagnetic dosimetry of children head for portable telephones, the dielectric properties of biological tissues for adults are so far being used due to the lack of children's ones. In this paper, based on the data measured by Peyman et al for complex permittivity of rats, we derived an approximated formula for the complex permittivity of various tissues as a function of age. Applying the formula to the dielectric properties of 7-year-old and 3-year-old children head models, we analyzed numerically the spatial peak SAR for a 900 MHz portable telephone with respect to the age. As a result, we found that the dielectric properties-for the children head models do not affect significantly the one-gram or ten-gram averaged spatial peak SAR, and they decrease the ten-gram averaged spatial peak SAR in the brain. The latter finding was validated via calculating the SAR penetration depth, and the former finding could be explained as an offset effect of the SAR increase at surface tissues and the rapid SAR decrease in depth tissues due to the higher dielectric properties of children than those of adults.