An Investigation of the SAR Distribution in Bone Marrow with Possible Non-Thermal Effects

An Investigation of the SAR Distribution in Bone Marrow with Possible Non-Thermal Effects

The power absorption due to EMF radiation is calculated, in bone and bone marrow. The EMF employed in various communication and technological applications indicate undeniable effect on humans both as public and occupational environments. These EMF effects arouse from electronic devices such as, cellular phones and their networks, wi-fi routers, microwave transmitters, antennae, etc. besides the upcoming 5G generation and their extended applications. EMF exposure effects are estimated by either animal experimentation or phantom model assessments. Moreover computer modelling, either stochastic or deterministic, besides epidemiological studies are taken into account as well. A deterministic mathematical model is constructed and applied, using the reported frequency dependent electromagnetic properties, for bone and bone marrow. The specific absorption rate (SAR), in both anatomic structures, is computed according to the present mathematical model, is represented spatially in the bone-marrow-bone layers under study. The effect of exposure to electric field of strengths ranging from 1V/m to 1kV/m is investigated for a wide frequency spectrum in each layer of the proposed model.  The frequency dependence of the SAR, through these layers, is illustrated for frequencies ranging from 1kHz to1GHz. The thermal and non-thermal power densities are calculated for an extended frequency range from (10MHz-100GHz).The present results are in agreement with international safety standards for applied field strengths of maximum value; 10V/m for bone and 100V/m for bone marrow. Furthermore, the present model shows that oblique incidence results in higher SAR values than with normal incidence, highly evident for low frequency, especially for the frequency 1kHz. Higher absorption rates are exhibited by frequencies around 10MHz than those exhibited by frequencies in the range 1GHz to10GHz.  The model, developed by this study, provides a possibility for establishment of some features or changes in the assessed biological parameters, which couldn’t be established by other methods applied. The author suggests introducing standardization for the non-thermal power and giving its assessment considerable attention by the international organizations.

Aim:  Deterministic evaluation of the microwave power density distribution and absorption, in long bone and bone marrow, due to far field exposure.

Study Design:  A mathematical model is constructed and applied to a bone –bone marrow-bone section to simulate EMF propagation and hence absorption in each layer.

Place and Duration of Study: Department of Engineering Math. And Physics Dept., Fac. Of Engineering, Cairo University.

Methodology: The author employs a bone-marrow-bone model to investigate the effect of incident EMF. The equations governing the total electric and magnetic field distributions in each layer are deduced, considering its biological electromagnetic properties. The model is simulated by a computer program using Maple V. The computed values of real and imaginary components of power density in bone and bone marrow are graphically represented versus frequency. The exposure to electric field of strength ranging from 1V/m to 1kV/m is investigated using the proposed method. The frequency dependence of the power density, both dissipated and stored, through the bone-marrow-bone layers is illustrated for a frequency range of 1kHz-10GHz.

Results: Electromagnetic radiation of 1MHz-10MHz induce absorbed power within the safety limits for all applied field strengths. The 1GHz incident radiation induces SAR values higher than permissible ranges for field strengths above 400V/m whereas the same occurs for a low frequency range at 100V/m. Moreover, the present results are in agreement with international safety standards for applied filed strengths till 10V/m for bone and till 100V/m for bone marrow, covering the applied frequencies (1 kHz -1 GHz). Except for exposure to electric field of strength higher than 100V/m, the SAR acquired by the bone marrow is within the safety levels. These results also show that the non-thermal power densities are more effective for the UHF range 100MHz-100GHz.

Conclusion: The results obtained are in agreement with international safety standards for filed strengths of maximum value 10V/m for bone and 100V/m for bone marrow. Oblique incidence results in higher SAR values than normal incidence, especially for low frequency (1kHz). Non-thermal effects should be given further consideration especially for UHF ranges.

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