The dependence of EM energy absorption upon human head modeling at 900 MHz

Abstract

Abstruct-In this papier the dependence of electromagnetic energy absorption at 900 IMHz in the human head on its anatomy and its modeling are investigated for RF-sources operating in the very close proximity of the head. Different numerical head phantoms based on MRI scans of three different adults were used with voxel sizes down to 1 mm:'. Simulations of the absorption were performed by distinguishing the electrical properties of up to 13 tissue types. In addition simulations with modified electric parameters and reduced degrees of complexity were performed. Thus, the phantoms greatly differ from each other in terms of shape, size, and internal anatomy. The numerical results are compared with those of measurements in a multitissue phantom and two homogeneous phantoms of different shapes and sizes. The results demonstrate that size and shape are of minor importance. Although local SAR values depend significantly on local inhomogeneities and elecctric properties, the volume-averaged spatial peak SAR obtained with the homogeneous phantoms only slightly overestimates that of the worst-case exposure in the inhomogeneous phantoms.

Prediction of the Sar Level Induced in a Dielectric Sphere by a Thin Wire Dipole Antenna

“…Similar results were derived with the same method in [19]. Moreover, in [20,21] the use of different configurations of the human head coupled to a dipole antenna, pointed out that the average spatial peak SAR values are slightly dependent on the shape, size or whether the phantom is homogeneous or not. The homogeneous representation of the human phantom is proposed in these studies, as it reduces the number of tests (due to the symmetry of the antenna that is observed at the direction parallel to the surface), without simultaneously overestimating the average spatial peak SAR values.…”

Analysis of Current Density and Specific Absorption Rate in Biological Tissue Surrounding Transcutaneous Transformer for an Artificial Heart

“…SAR is evaluated by two methods: one experimental and one analytical. In the experimental method, the electrical field in a liquid phantom is measured [19] or the temperature rise in a solid phantom is measured and commuted to SAR [20]. It is difficult, however, to correctly measure the temperature rise with these methods because there is not only a temperature increase in the phantom due to the electromagnetic field but also a temperature increase in the transcutaneous transformer due to copper loss.…”

Modelling the Interaction between the Antenna and the Human Head by the Technique of Artificial Neural Network

“…According to the working frequency, the antenna power, the power radiated by the antenna, the dielectric properties of tissues, the distance between the antenna and the head gives a look of reflection coefficient, a SAR value (between 10 and 1 g), the value of radiation efficiency, the value of the input power, the input impedance. So from this explanation, we have took as input the reflection coefficient of the antenna, the working frequency, the distance d between the antenna and the body, the input power, the output power, the permittivity of fabric, the fabric density and the conductivity of tissue and as an output they obtained the reflection coefficient, the SAR values averaged over 10 and 1 g (Hombach et al, 1996;Okoniewski and Stuchly, 1996;Kouveliotis and Panagiotou, 2006;Sager et al, 2003), the radiation efficiency, the power absorbed and the input impedance. Figure 3 shows the Neural model applied to the interaction.…”