Calculation of Specific Absorption Rate at Four Tissue Layers Using One Dimensional FDTD Method

Abstract

The wider usage of mobile phone usage in recent years has dramatically increased our exposure to electromagnetic waves. Standards have
been developed for limiting exposure to electromagnetic waves. One of the measures that defines the effect of electromagnetic wave is specific
absorption rate(SAR). Specific absorption rate is a measure of the rate of electromagnetic energy absorbed by body tissues or electromagnetic
power absorbed by unit tissue. Since calculating SAR with analytical methods is very difficult, numerical methods are preferred. In this study,
SAR values were calculated using the Finite Difference Time Domain(FDTD) method. FDTD method, relies on the discretization the partial
differential Maxwell equations in space and time using the finite difference approach. FDTD method is used to simulate electromagnetic wave
propagation. For the SAR calculation, a 4-layer structure consisting of skin, fat, muscle and bone tissues has been created. Sinusoidal sources
with frequencies of 10 MHz and 900 MHz are used. When the wavelength is too large for the tissue thickness, the wave penetrates deeper into
the tissue. Within the tissue, the electric field is in close proximity. At 900 MHz the wave penetrates less to the tissues and most of the energy
is absorbed in the initial tissues. SAR values within the tissues are given in graphs.