Comparison of cardiac-induced endogenous fields and power frequency induced exogenous fields in an anatomical model of the human body.
Time-domain potentials measured at 64 points on the surface of a large canine heart, considered comparable with those of a human heart, were used to calculate the electric fields and current densities within various organs of the human body. A heterogeneous volume conductor model of an adult male with a resolution of approximately 6 mm3 and 30 segmented tissue types was used along with the admittance method and successive over-relaxation to calculate the voltage distribution throughout the torso and head as a function of time. From this time-domain voltage description, values of [E(t)] and [J(t)] were obtained, allowing for maximum values to be found within the given tissues of interest. Frequency analysis was then used to solve for [E(f)] and [J(f)] in the various organs, so that average, minimum and maximum values within specific bandwidths (0-40, 40-70 and 70-100 Hz) could be analysed. A comparison was made between the computed results and measured data from both EKG waveforms and isopotential surface maps for validation, with good agreement in both amplitude and shape between the computed and measured results. These computed endogenous fields were then compared with exogenous fields induced in the body from a 60 Hz high-voltage power line and a 60 Hz uniform magnetic field of 1 mT directed from the front to the back of the body. The high-voltage power line EMFs and 1 mT magnetic field were used as 'bench' marks for comparison with several safety guidelines for power frequency (50/60 Hz) EMF exposures. The endogenous electric fields and current densities in most of the tissues (except for organs in close proximity to the heart, for example lungs, liver, etc) in the frequency band 40-70 Hz were found to be considerably smaller, between 5% and 10%, than those induced in the human body by the electric and magnetic fields generated by the 60 Hz sources described above.
Hart
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University of Utah, Department of Electrical Engineering, Salt Lake City 84112-9202, USA.
Gandhi
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D000328:Adult; D000818:Animals; D001921:Brain / Q000502:physiology; D004285:Dogs; D004553:Electric Conductivity; D004562:Electrocardiography; D004574:Electromagnetic Fields / Q000009:adverse effects; D017408:Guidelines as Topic; D006321:Heart / Q000502:physiology*; D006801:Humans; D008099:Liver / Q000502:physiology; D008297:Male; D008953:Models, Anatomic