Temperature Rise in Human Tissue from SAR

Christopher W. Penney and Raymond J. Luebbers

Remcom Incorporated

315 South Allen Street, Suite 222

State College, PA 16801, USA

cwp@remcom.com, rjl@remcom.com

Abstract: The temperature rise in a human head caused by absorbed power in the form

of SAR from a cellular telephone is computed using a bio-heat equation approach.  The

SAR is computed using an FDTD solver for a reasonable cellular telephone model that

radiates at both 900 and 1800 MHz. The impact on the SAR and temperature rise from

the human hand holding the telephone is evaluated and compared to the case of the head

alone. The inclusion of the hand has an effect of decreasing the temperature rise in the

head. In the case of 1800MHz, the temperature rise in the entire geometry was higher

with the hand present due to a larger increase in the thumb.

Keywords: SAR, Temperature Rise, Bioheat, FDTD

1. Introduction

The topic of temperature rise in human tissue caused by exposure to

electromagnetic fields, particularly those radiated by wireless devices, has been of

interest for several years. The issue of temperature rise in the eye [1]-[4] caused by

electromagnetic fields has generated some interest due to the low blood flow through the

eye tissue.  While some work has been performed to detail the effects of far-field

radiation on temperature rise [5], most research has concerned radiation from nearby

sources such as dipoles [6][7] or handsets[8]-[12]. Essentially all work makes use of a

bio-heat equation, such as that described by Pennes [13].  This effort makes use of the

Pennes bio-heat equation in the form used by Collins [14]. The goal of this work was to

determine the impact on temperature rise of including the human hand holding a cellular

telephone placed next to the head.

2. Method

The approach used in this work follows that developed by Collins [14] which uses

the Pennes bio-heat equation in the form

ρc dT/dt = ∇ · (k∇T) + [-ρbloodwcblood(T­ Tcore)] + Qm + SARρ

Here T represents the temperature of the tissue in degrees Celsius, ρ is the material

density (kg/m3), c is the heat capacity (J/kg/oC), k is the thermal conductivity (W/m/°C),