291
Mobile Communication Fields in Biological Systems
SAR results for typical exposure conditions, without being possibly able to provide the
worst-case SAR.
However, the aforementioned definitions for “cheek” and “tilted” are not directly
applicable to anatomical head models other than SAM. Anatomical head models have
varying reference planes and points, pinna shape, and size and misalignment with the
computational grid. Therefore, positioning of the cellular phone on anatomical head
models other than SAM is a complex and nonstandardized procedure. In order to assure
that positioning of the cell phone relative to the head model is the same among different investigators and to avoid ambiguities in the numerical dosimetry results of several
research groups, as in Kainz et al. (2005), the phone positioning definitions for the SAM
model were extended and a formal definition was proposed for the positioning of cellular phones next to anatomical head models. A procedure for determining reference
planes and reference points based only on anatomical characteristics of the head model
was described and, based on these, the “cheek” and “tilted” positions were subsequently
defined. All definitions were based on anatomical characteristics of the head and tested
by evaluating SAR data in 14 different head models and comparing them with the SAM
model used in the CENELEC and IEEE standard procedures.
5.4.1.3 Dosimetry Results
The results of the cellular phone dosimetry studies are usually given in the form of crosssectional graphs, 2D contour plots or 3D color graphs of SAR distributions, often averaged over 1 g or 10 g of tissue for immediate comparison with the exposure guidelines
(IEEE 2005; ICNIRP 1998). The derived dosimetric quantities have been found to highly
depend on the numerical/experimental phantom used, the EM radiation frequency, the
phone model (or, equivalently, the antenna type) and the distance between the cellular
phone and the head.
The dependence of the SAR values on the head phantom has been extensively studied
in the literature. In the “cellular phone standard” (CEPHOS) project, the head model
was found to strongly disturb the symmetry of the antenna radiation pattern in the
direction of the head. A cubic box head model drastically reduced the radiation in the
head direction, while in the case of a spherical head model, there was a less dramatic
but significant reduction in power radiated toward the head. Homogeneous sphere
head models gave increased values for local and averaged SARs compared to layered
ones. Furthermore, a large number of studies evaluating the peak spatial SAR in the
SAM phantom with respect to anatomical head models concluded that the peak spatial
SAR assessed with the SAM is a conservative measure for the exposure (Christ et al.
2005; Dominguez, Raizer, and Carpes 2002; Martens 2005). The handling of the phone
will also have a considerable impact on the EM interaction between cellular phone and
human. For example, in Table 5.2, two handset-handling scenarios are considered at
900 MHz and the peak SAR values along with the power absorbed in the head and
hand are recorded (Al-Mously and Abousetta 2008). A heterogeneous high-resolution
European female head model, a mobile phone equipped with an external antenna, and
an antenna input power of 600 mW have been assumed. In a certain usage pattern of the
cellular phone with a left-side external antenna, the maximum percentage difference of
the spatial peak 1 g avg SAR values in the head due to the right hand-hold alteration may
Mobile Communication Fields in Biological Systems
SAR results for typical exposure conditions, without being possibly able to provide the
worst-case SAR.
However, the aforementioned definitions for “cheek” and “tilted” are not directly
applicable to anatomical head models other than SAM. Anatomical head models have
varying reference planes and points, pinna shape, and size and misalignment with the
computational grid. Therefore, positioning of the cellular phone on anatomical head
models other than SAM is a complex and nonstandardized procedure. In order to assure
that positioning of the cell phone relative to the head model is the same among different investigators and to avoid ambiguities in the numerical dosimetry results of several
research groups, as in Kainz et al. (2005), the phone positioning definitions for the SAM
model were extended and a formal definition was proposed for the positioning of cellular phones next to anatomical head models. A procedure for determining reference
planes and reference points based only on anatomical characteristics of the head model
was described and, based on these, the “cheek” and “tilted” positions were subsequently
defined. All definitions were based on anatomical characteristics of the head and tested
by evaluating SAR data in 14 different head models and comparing them with the SAM
model used in the CENELEC and IEEE standard procedures.
5.4.1.3 Dosimetry Results
The results of the cellular phone dosimetry studies are usually given in the form of crosssectional graphs, 2D contour plots or 3D color graphs of SAR distributions, often averaged over 1 g or 10 g of tissue for immediate comparison with the exposure guidelines
(IEEE 2005; ICNIRP 1998). The derived dosimetric quantities have been found to highly
depend on the numerical/experimental phantom used, the EM radiation frequency, the
phone model (or, equivalently, the antenna type) and the distance between the cellular
phone and the head.
The dependence of the SAR values on the head phantom has been extensively studied
in the literature. In the “cellular phone standard” (CEPHOS) project, the head model
was found to strongly disturb the symmetry of the antenna radiation pattern in the
direction of the head. A cubic box head model drastically reduced the radiation in the
head direction, while in the case of a spherical head model, there was a less dramatic
but significant reduction in power radiated toward the head. Homogeneous sphere
head models gave increased values for local and averaged SARs compared to layered
ones. Furthermore, a large number of studies evaluating the peak spatial SAR in the
SAM phantom with respect to anatomical head models concluded that the peak spatial
SAR assessed with the SAM is a conservative measure for the exposure (Christ et al.
2005; Dominguez, Raizer, and Carpes 2002; Martens 2005). The handling of the phone
will also have a considerable impact on the EM interaction between cellular phone and
human. For example, in Table 5.2, two handset-handling scenarios are considered at
900 MHz and the peak SAR values along with the power absorbed in the head and
hand are recorded (Al-Mously and Abousetta 2008). A heterogeneous high-resolution
European female head model, a mobile phone equipped with an external antenna, and
an antenna input power of 600 mW have been assumed. In a certain usage pattern of the
cellular phone with a left-side external antenna, the maximum percentage difference of
the spatial peak 1 g avg SAR values in the head due to the right hand-hold alteration may