Parametric dependence of SAR on permittivity values in a man model

Abstract

The development and widespread use of advanced three-dimensional digital anatomical models to calculate specific absorption rate (SAR) values in biological material has resulted in the need to understand how model parameters (e.g., permittivity value) affect the predicted whole-body and localized SAR values. The application of the man dosimetry model requires that permittivity values (dielectric value and conductivity) be allocated to the various tissues at all the frequencies to which the model will be exposed. In the 3-mm-resolution man model, the permittivity values for all 39 tissue-types were altered simultaneously for each orientation and applied frequency. In addition, permittivity values for muscle, fat, skin, and bone marrow were manipulated independently. The finite-difference time-domain code was used to predict localized and whole-body normalized SAR values. The model was processed in the far-field conditions at the resonant frequency (70 MHz) and above (200, 400, 918, and 2060 MHz) for E orientation. In addition, other orientations (K, H) of the model to the incident fields were used where no substantial resonant frequency exists. Variability in permittivity values did not substantially influence whole-body SAR values, while localized SAR values for individual tissues were substantially affected by these changes. Changes in permittivity had greatest effect on localized SAR values when they were low compare to the whole-body SAR value or when errors involved tissues that represent a substantial proportion of the body mass (i.e., muscle). Furthermore, we establish the partial derivative of whole-body and localized SAR values with respect to the dielectric value and conductivity for muscle independently. It was shown that uncertainties in dielectric value or conductivity do not substantially influence normalized whole-body SAR. Detailed investigation on localized SAR ratios showed that conductivity presents a more substantial factor in absorption of energy in tissues than dielectric value for almost all applied exposure conditions.

Analysis of Absorption Loss by a Human Body in On-to-Off Body Communication at 2.45 GHz

“…The dielectric properties are defined in terms of relative permittivity and conductivity , and their numerical values for the simulations are described in Table 2. The absorption is well-known to depend more on conductivity than on relative permittivity; namely, as conductivity increases, the AL also increases [12,13].…”

Non-Invasive in vivo Loss Tangent Imaging: Thermal Sensitivity Estimation at the Larmor Frequency

“…As the frequency of the RF wave increases, the heating process is also influenced by displacement current (J d ) due to polarization. Therefore, permittivity should also be considered for predicting temperature elevation (11). The effects of both conductivity and permittivity can be observed simultaneously using the dielectric loss tangent, which is a characteristic of materials.…”

Study of Channel Model Characterization of Human Internal Organ in On-Body System at 2.45 GHz

“…Properties of body tissues [18] . [13], [14] . 유전율과 전도도 이외에도 전파 흡수율에 영향을 주는 여러 요소가 존재한다 [15]～ [17] .…”