title: Estimation of the whole-body averaged SAR of grounded human models for plane wave exposure at respective resonance frequencies.
abstract: 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.
authors.affiliation: Nagoya Institute of Technology, Department of Computer Science and Engineering, Japan. ahirata@nitech.ac.jp
authors.forename: Akimasa
authors.initials: A
authors.lastname: Hirata
authors.forename: Kazuya
authors.initials: K
authors.lastname: Yanase
authors.forename: Ilkka
authors.initials: I
authors.lastname: Laakso
authors.forename: Kwok Hung
authors.initials: KH
authors.lastname: Chan
authors.forename: Osamu
authors.initials: O
authors.lastname: Fujiwara
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Nagaoka
authors.forename: Soichi
authors.initials: S
authors.lastname: Watanabe
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Conil
authors.forename: Joe
authors.initials: J
authors.lastname: Wiart
mesh_terms: D000042:Absorption; D000328:Adult; D049628:Body Size; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure / Q000032:analysis*; D005260:Female; D006801:Humans; D008297:Male; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D051598:Whole Body Imaging / Q000295:instrumentation*