Evaluation of SAR and Temperature Rise in Human Hand Due to Contact Current From 100 kHz to 100 MHz

Abstract

International guidelines/standards for the protection of humans from radiofrequency exposure have set a limit by assuming the lowest threshold for a classical heating effect, among other effects. However, no computational study has been reported that evaluates temperature rise due to contact currents. This paper presents the computational dosimetry of a specific absorption rate (SAR) and temperature rise due to touch contact currents in the frequency range 100 kHz to 100 MHz using a detailed numerical model of a human hand. Tissue dielectric properties obtained from a conventional 4-Cole-Cole dispersion model have often been considered in dosimetry studies. However, a comparison of the computed electrical impedance with experimental results suggests that the conductivity of the subcutaneous fat in the finger should be higher than the 4-Cole-Cole values-potentially attributable to collagen fibers. We then proposed a set of tissue dielectric conductivities estimated from recent measurement results of conductivities for the epidermis, dermis, and subcutaneous tissue. Consequently, the computed electrical impedances exhibited good agreement with the measured ones. In addition, the SAR and temperature rise obtained using the proposed tissue conductivities were lower than those obtained using 4-Cole-Cole values. Therefore, the SAR and temperature rise obtained based on the 4-Cole-Cole dispersion model may be overstated. We also observed that the steady-state maximum temperature rise due to the contact current at the guidance/limit level was equivalent to 2.5 °C, which is the maximum permissible temperature rise (5 °C) divided by a reduction factor of 2.