SUMMARY The assessment of radiofrequency exposure level and the exposure setup are critical, because if the exposure levels (related to frequency, power, position, and other variables) are not known, the biological results are not meaningful. In this regard, this study aims to design, implement, and analyze numerical setups for the simulations of radiofrequency exposure related specific absorption rate and temperature increase in the human brain and head. For this purpose, specific models for human head and telephone antenna are chosen, and the FEM is selected for solving PDEs related to electromagnetic wave equations and bioheat equation. After the verification of the methodology chosen by achieving comparable results with the literature, the scope of the study is then turned to the effects of different parameters on the exposure levels. In the end, comprehensive information can be obtained from the simulation results so that risk management policies for electromagnetic radiation can be reevaluated to minimize the possible health hazards. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, the numerical modeling of interaction between light sources and living biological tissue is studied. One of the most important results of physical interactions of light with biological tissue are thermal changes, which are a consequence of absorption of light. The severity of the effects is dependent upon several factors, including exposure duration, wavelength of the beam, beam energy, tissue type, and the area that is exposed to the beam. The temperature response of tissue irradiation is governed by the extensively used Pennes bioheat equation in a 3-dimensional space. The Pennes equation is solved initially for a single-layer human skin model, thanks to which temperature distribution can be predicted using different laser light radiation burns at steady state. Furthermore, a multilayer model is used to investigate the effects of the energy of the beam and exposure duration. The numerical solutions are obtained by the finite element method (FEM), in which the geometry studied is divided into a finite element mesh. This method gives a better description of the geometry with a smaller number of nodes when compared with the finite difference time domain (FDTD) method. Using the FDTD method, which may require spatial step ranges to achieve convergence, makes the computational simulation time increase dramatically. On the contrary, less memory space and disk space with shorter run times make the FEM more advantageous than other numerical solution techniques and that is why this method has been chosen for this study. Temperature contours and penetration depths are plotted in 3-dimensional spaces. In this work it is demonstrated that by adjusting the exposure duration, wavelength of the beam, energy of the beam, and the area and type of tissue, temperature effects of light on tissue can be altered.

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