Numerical dosimetry at power-line frequencies using anatomically based models

Abstract

We have used the finite-difference time-domain (FDTD) method to calculate induced current densities in a 1.31-cm (nominal 1/2 in) resolution anatomically based model of the human body for exposure to purely electric, purely magnetic, and combined electric and magnetic fields at 60 Hz. This model based on anatomic sectional diagrams consists of 45,024 cubic cells of dimension 1.31 cm for which the volume-averaged tissue properties are prescribed. It is recognized that the conductivities of several tissues (skeletal muscle, bone, etc.) are highly anisotropic for power-line frequencies. This has, however, been neglected in the first instance and will be included in future calculations. Because of the quasi-static nature of coupling at the power-line frequencies, a higher quasi-static frequency f' may be used for irradiation of the model, and the internal fields E' thus calculated can be scaled back to the frequency of interest, e.g., 60 Hz. Since in the FDTD method one needs to calculate in the time domain until convergence is obtained (typically 3-4 time periods), this frequency scaling to 5-10 MHz for f' reduces the needed number of iterations by over 5 orders of magnitude. The data calculated for the induced current and its variation as a function of height are in excellent agreement with the data published in the literature. The average current densities calculated for the various sections of the body for the magnetic field component (H) are considerably smaller (by a factor of 20-50) than those due to the vertically polarized electric field component when the ratio E/H is 377 ohms. We have also used the previously described impedance method to calculate the induced current densities for the anatomically based model of the human body for the various orientations of the time-varying magnetic fields, namely from side to side, front to back, or from top to bottom of the model, respectively.

Analysis of the Whole-Body Averaged Specific Absorption Rate (Sar) for Far-Field Exposure of an Isolated Human Body Using Cylindrical Antenna Theory

“…Poljak and Roje [9] utilized the method of moments (MoM) to compute currents in a thick-wire model of human body in ELF exposure by employing the exact kernel of the Pocklington integro-differential equation. Both approaches provided reasonably accurate results compared to the results found using the finite-difference time-domain (FDTD) algorithm on voxel-based models of the human body [10]. King extended his studies to 150 MHz [11] using similar analytic approaches; but the results were not as accurate as results reported by other authors.…”

Wireless Phones Electromagnetic Field Radiation Exposure Assessment

“…Various techniques for determination of internal field at near field in the body tissue can be found in [8][9][10] . The heating effect is directly related to the total power absorbed by human body.…”

Simplified modeling of the human body exposed to power substation electric field using boundary element analysis

“…This equation can be derived starting from the time harmonic Maxwell's equations. The Pocklington integro-differential equation which determines the current along a thick wire is given by [3,9]: (8) where E z inc is the corresponding incident field, I(z) is the axial current distribution Z L (z) is the impedance per unit length of the cylinder, and g E (z, z') is the kernel of the integral equation which is given by [3,9]: (9) in which R denotes the distance from the source point z to the observation point z', where both are located on the thick wire antenna surface, therefore:…”

“…The assessment of the current density induced in the human body due to ELF exposures, mostly to power lines, has already been reported by some researchers having used either analytical [1,2], or numerical techniques [6][7][8][9][10].…”