Determination of Power Absorption in Man Exposed to High Frequency Electromagnetic Fields by Thermographic Measurements on Scale Models

When the body of man, small compared to a wavelength, is exposed to high frequency (HF) electromagnetic (EM) fields, the absorbed power density patterns and total absorbed power may be approximated by the simple superposition of the internal electric fields obtained from the quasistatic coupling characteristics of the electric and magnetic field components determined independently. These characteristics were obtained for full scale man by thermographic studies of power absorption in scale models of man exposed to fields at frequencies scaled up inversely proportional to the model size. A VHF resonant cavity was used to provide the necessary field strengths for producing measurable power absorption patterns under simulated HF exposure conditions. The results indicate that peak power absorption densities as high as 5.63 W/kg can be produced in man exposed to 10 mW/cm
2
31 MHz radiation fields. The results show that the absorption decreases as the square of the frequency as predicted by theory for frequencies below 31 MHz.