Estimation of the whole-body averaged SAR of grounded human models for plane wave exposure at respective resonance frequencies

According to the international guidelines, the whole-body averaged specific absorption rate (WBA-SAR) is used as a metric of basic restriction for radio-frequency whole-body exposure. It is well known that the WBA-SAR largely depends on the frequency of the incident wave for a given incident power d...

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Bibliographic Details
Published in:Physics in medicine & biology 2012-12, Vol.57 (24), p.8427-8442
Main Authors: Hirata, Akimasa, Yanase, Kazuya, Laakso, Ilkka, Chan, Kwok Hung, Fujiwara, Osamu, Nagaoka, Tomoaki, Watanabe, Soichi, Conil, Emmanuelle, Wiart, Joe
Format: Article
Language:English
Subjects:
Absorption
Adult
Body Size
Child
Child, Preschool
Environmental Exposure - analysis
Female
Humans
Male
Phantoms, Imaging
Radiation Dosage
safety guidelines for electromagnetic waves
specific absorption rate
Whole Body Imaging - instrumentation
whole-body exposure
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Summary:According to the international guidelines, the whole-body averaged specific absorption rate (WBA-SAR) is used as a metric of basic restriction for radio-frequency whole-body exposure. It is well known that the WBA-SAR largely depends on the frequency of the incident wave for a given incident power density. The frequency at which the WBA-SAR becomes maximal is called the 'resonance frequency'. Our previous study proposed a scheme for estimating the WBA-SAR at this resonance frequency based on an analogy between the power absorption characteristic of human models in free space and that of a dipole antenna. However, a scheme for estimating the WBA-SAR in a grounded human has not been discussed sufficiently, even though the WBA-SAR in a grounded human is larger than that in an ungrounded human. In this study, with the use of the finite-difference time-domain method, the grounded condition is confirmed to be the worst-case exposure for human body models in a standing posture. Then, WBA-SARs in grounded human models are calculated at their respective resonant frequencies. A formula for estimating the WBA-SAR of a human standing on the ground is proposed based on an analogy with a quarter-wavelength monopole antenna. First, homogenized human body models are shown to provide the conservative WBA-SAR as compared with anatomically based models. Based on the formula proposed here, the WBA-SARs in grounded human models are approximately 10% larger than those in free space. The variability of the WBA-SAR was shown to be ±30% even for humans of the same age, which is caused by the body shape.
ISSN:0031-9155
1361-6560
DOI:10.1088/0031-9155/57/24/8427