Variability in EMF permittivity values: Implications for SAR calculations

Digital anatomical models of man and animals are available for use in numer ical calculations to predict electromagnetic field (EMF)-induced specific a bsorption rate (SAR) values, To use these models, permittivity values are a ssigned to the various tissues for the EMF frequencies of interest, There i s, as;ret, no consensus on what are the best permittivity data. This study analyzed the variability in published permittivity data and investigated th e effects of permittivity values that are proportional on SAR calculations. Whole-sphere averaged and localized SAR values along the diameter of a 4-c m sphere are calculated for EMF exposures in the radio frequency range of I MHz to 1 GHz. When the dimensions of a sphere are small compared to the wa velength (i.e., wavelength inside the material is greater than ten times th e dimensions of the object), the whole-sphere averaged SAR is inversely pro portional to the permittivity of the material composing the sphere, However , the localized SAR values generally do not hare the same relation and, as a matter of fact, vary greatly depending on the location within the sphere, These results indicate that care must be taken in choosing the permittivit y values used in calculating SAR values and some estimate of the dependence of the calculated SAR values on variability in permittivity should be dete rmined.