title: Stochastic method for determination of the organ-specific averaged SAR in realistic environments at 950 MHz.
abstract: The organ-specific averaged specific absorption rate (SARosa ) in a heterogeneous human body phantom, the Virtual Family Boy, is determined for the first time in five realistic electromagnetic environments at the Global System for Mobile Communications downlink frequency of 950 MHz. We propose two methods based upon a fixed set of finite-difference time-domain (FDTD) simulations for generating cumulative distribution functions for the SARosa in a certain environment: an accurate vectorial cell-wise spline interpolation with an average error lower than 1.8%, and a faster scalar linear interpolation with a maximal average error of 14.3%. These errors are dependent on the angular steps chosen for the FDTD simulations. However, it is demonstrated that both methods provide the same shape of the cumulative distribution function for the studied organs in the considered environments. The SARosa depends on the considered organ and the environment. Two factors influencing the SARosa are investigated for the first time: conductivity over the density ratio of an organ, and the distance of the organ's center of gravity to the body's surface and exterior of the phantom. A non-linear regression with our model provides a correlation of 0.80. The SARosa due to single plane-wave exposure is also investigated; a worst-case single plane-wave exposure is determined for all studied organs and has been compared with realistic SARosa values. There is no fixed worst-case polarization for all organs, and a single plane-wave exposure condition that exceeds 91% of the SARosa values in a certain environment can always be found for the studied organs.
authors.affiliation: Department of Information Technology, Ghent University/iMinds, Ghent, Belgium.
authors.forename: Arno
authors.initials: A
authors.lastname: Thielens
authors.forename: Günter
authors.initials: G
authors.lastname: Vermeeren
authors.forename: Wout
authors.initials: W
authors.lastname: Joseph
authors.forename: Luc
authors.initials: L
authors.lastname: Martens
mesh_terms: D000042:Absorption; D002648:Child; D055590:Electromagnetic Phenomena; D004777:Environment; D006112:Gravitation; D006801:Humans; D008297:Male; D009928:Organ Specificity; D019047:Phantoms, Imaging; D011874:Radiometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D013269:Stochastic Processes
keywords: organ-specific averaged SAR; realistic electromagnetic environment