The objective of the study was to theoretically examine the stimulation threshold of large myelinated axons and to use the results to formulate criteria for exposure limits of pulsed magnetic fields.
The induced electric fields were calculated with a homogeneous tissue equivalent prolate spheroid.
The stimulation level of the field was computed with the SENN model by using a folded axon with 2 mm separation for the Ranvier nodes.
In the case of rectangular induced electric field pulses, the asymptotic stimulation level for electric field strength was 10 Vm-1 with pulse durations greater than 100 mus and for integrated electric field strength 1 x 10-3 V m-1 s with pulse durations less than 100 mus.
The latter threshold level was exceeded in the surface of the prolate spheroid when the magnetic flux density changed by more than 7.4 mT within 100 mus.
For sinusoidal bursts, the threshold amplitude of the magnetic field decreased asymptotically to a minimum value 2.5 mT when the carrier frequency and burst duration exceeded 5 kHz and 100 mus, respectively.
If the same safety criteria are applied for pulsed and continuous exposure, the peak limits for induced current densities and magnetic field can exceed the amplitude values of the limits for continuous exposure only by a factor varying from 3 to 10.
Mots-clés Pascal : Champ électromagnétique, Rayonnement non ionisant, Champ impulsionnel, Etude théorique, Fibre nerveuse myélinisée, Seuil entraînement, Stimulation, Exposition, Dose limite, Norme sécurité, Modélisation, Estimation paramètre, Durée impulsion, Niveau énergie
Mots-clés Pascal anglais : Electromagnetic field, Non ionizing radiation, Pulsed field, Theoretical study, Myelinated nerve fiber, Stimulus threshold, Stimulation, Exposure, Limit dose, Safety standard, Modeling, Parameter estimation, Pulse width, Energy level
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 97-0188514
Code Inist : 002A08F01. Création : 21/05/1997.