Temperature distributions in the human leg for VLF-VHF exposures at the ANSI-recommended safety levels

Using a block model of 1532 cubical cells, temperature distributions are calculated for the lowest 21 cm of the human leg for electric fields recommended in the ANSI RF safety guideline. The thermal model uses inhomogeneous volume-averaged tissue properties: blood-flow rate, metabolism, thermal conductivity, specific heat, etc. The SARs are obtained using the impedance method. A modified finite-difference technique is used to solve the 3-D heat-conduction equation for the thermal model. Numerical results are obtained for RF currents at 3 and 40 MHz projected for the E fields recommended by the ANSI Standard (614 and 61.4 V/m, respectively) and also for power densities one-tenth of that level. Temperatures as high as 41.6 degrees C are obtained for some internal cells for the higher E fields while relatively moderate temperatures on the order of 37 degrees C are obtained for the lower E fields. Some of the calculated results for the surface temperature have been compared and found to be in good agreement with the experimental data for initial rates of heating.