title: SAR variation study from 300 to 5000 MHz for 15 voxel models including different postures.
abstract: An extensive study on specific absorption rate (SAR) covering 720 simulations and 15 voxel models (18-105 kg) has been performed by applying the parallel finite-difference time-domain method. High-resolution whole-body models have been irradiated with plane waves from 300 MHz to 5 GHz by applying various incoming directions and polarizations. Detailed results of whole-body SAR and peak 10 g SAR are reported, and SAR variation in the dB scale is examined. For an adult, the effect of incoming direction on whole-body SAR is larger in the GHz range than at around 300-450 MHz, and the effect is stronger with vertical polarization. For a child (height approximately 1.2 m), the effect of incoming direction is similar as for an adult, except at 300 MHz for horizontal polarization. The effect of the phantom (18-105 kg) on whole-body SAR is larger at around 2-5 GHz and at vertical 300 MHz (proximity of whole-body resonance for the child) than at around horizontal 300-900 MHz. Body posture has little effect on whole-body SAR in the GHz range, but at around 300-450 MHz, one may even expect a 2 dB rise in whole-body SAR if posture is changed from the standing position. Posture affects peak 10 g SAR much more than whole-body SAR. The polarization of the incident electric field may have an effect of several dB on whole-body SAR. Between 2 and 5 GHz for adults, whole-body SAR is higher for horizontal than for vertical polarization, if the incoming direction is in the azimuth plane. In the GHz range, horizontal polarization gives higher whole-body SAR, especially for irradiation from the lateral direction. A comparison between homogeneous and heterogeneous models was done. A homogenized model underestimates whole-body SAR, especially at approximately 2 GHz. The basic restriction of whole-body SAR, set by ICNIRP, is exceeded in the smallest models ( approximately 20 kg) at the reference level of exposure, but also some adult phantoms are close to the limit. The peak 10 g SAR limits were never exceeded in the studied cases. The present ICNIRP guidelines should be revised by lowering the reference levels, especially at around 2-5 GHz.
authors.affiliation: Department of Radio Science and Engineering, Helsinki University of Technology, Otakaari 5A, 02150 Espoo, Finland. tero.uusitupa@tkk.fi
authors.forename: T
authors.initials: T
authors.lastname: Uusitupa
authors.forename: I
authors.initials: I
authors.lastname: Laakso
authors.forename: S
authors.initials: S
authors.lastname: Ilvonen
authors.forename: K
authors.initials: K
authors.lastname: Nikoskinen
mesh_terms: D000328:Adult; D002648:Child; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D019047:Phantoms, Imaging; D011187:Posture; D011827:Radiation; D011829:Radiation Dosage