In situ electric field dosimetry analysis for powerline frequency peripheral nerve magnetic stimulation

Area of Science:

• Biophysics
• Computational Electromagnetics
• Neuroscience

Background:

• Human exposure to 60 Hz magnetic fields (MFs) induces electric fields (EFs) and currents.
• Peripheral nervous system (PNS) stimulation thresholds from MFs are not well-defined.
• Existing models like the spatially extended nonlinear node (SENN) model are used for exposure guidelines, but newer models like McIntyre-Richardson-Grill (MRG) are emerging.

Purpose of the Study:

• To model a novel extremely low frequency MF exposure system for the human leg.
• To investigate in situ EFs at 60 Hz in the leg's skin and nerves.
• To compare EF induction using both the SENN and MRG models.

Main Methods:

• Designed a Helmholtz-like coil system using Biot-Savart and Faraday laws to generate EFs.
• Employed Sim4Life simulations with a detailed human body model.
• Assessed induced EFs at skin and nerve levels using SENN and MRG nerve excitation frameworks.

Main Results:

• High EF intensities were detected in sensory and sensory-motor nerves.
• The MRG model yielded lower stimulation thresholds compared to the SENN model.
• Nerve orientation significantly influences EF induction.

Conclusions:

• Comprehensive modeling is crucial for designing and validating MF exposure systems.
• Experimental data are essential for refining MF exposure models, standards, and guidelines.
• The MRG model shows promise for more accurate PNS stimulation threshold determination.