XIX Sympozjum Srodowiskowe PTZE - materialy.pdf

XIX Sympozjum PTZE, Worliny 2009
A STUDY ON SAR IN SPHEROIDAL MODELS
OF HUMAN BODY
Katarzyna Ciosk
Faculty of Electrical Engineering, Automatics and Computer Science,
Kielce University of Technology
The recent development of mobile communication and wireless networking of computer units
has resulted in an increasing public concern about the biological effects of electromagnetic
fields on the human body and about the possible impact of electromagnetic field on health.
The commonly adopted measure for the absorbed energy in biological tissues is the specific
absorption rate (SAR). Value of SAR depends on incident field parameters such the intensity,
polarization [1] and frequency [2] and on parameters of the body. Protection from potential
dangers is based on established safety guidelines, which propose maximum permissible
values for the SAR, in order to exclude or minimize the possibility of overexposure. The level
and distribution of radiofrequency energy absorbed in a child's body compared to those in an
adult body has been a controversial issue in recent years. It has been suggested that SAR has
higher value in children due to their smaller body size.
This paper presents the computation of the whole-body averaged SAR distribution inside a
prolate spheroidal model of human body exposed to far-field electromagnetic fields. The aim
of the paper is to investigate how the body parameters, such as size and parameters can
influence the energy absorption in biological matter. Apart from the effect of the body size,
the effect of higher values of the child tissues electrical properties on whole body SAR in
spheroidal biological model is examined. The focus of the present study is the effect of
polarization of incident electromagnetic waves on the SAR in different models. This is
because previous studies investigated the SAR for plane-wave exposure with H polarization
[4]. The electric field strength distribution inside the body were obtained by semi-analytical
method [3] and the whole-body specific absorption rate inside the spheroidal models ware
calculated. Time-harmonic fields with the time-dependence e jωt as a uniform plane wave were
suppressed. The external medium was assumed to be free space. The simulations were done
for frequencies ranging from 900 MHz to 3000 MHz. The absorption has been investigated
for 20 different dielectric prolate spheroidal human body models corresponding to dimensions
of human body. The spheroidal body dimensions taken into account are corresponding to
statistical data availabled on human height and weight of body. The electromagnetic
parameters are fitted to these models. The spheroid is an isotropic lossy dielectric. The
relative permittivity ε’-jε” and the conductivity of tissue depend on frequency. European
Standard EN-50361 establishes values of ε, γ for fantom liquid at mobile frequency band
300 – 3000MHz to be used in SAR calculations. The conductivity and permeability of tissues
of young organism are higher comparing to the adult organism. It is assumed that the decrease
in the dielectric properties values with age may be due to changes in the water content and the
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