Abstract
BackgroundPeripheral nerves are situated in a highly non-homogeneous environment, including muscles, bones, blood vessels, etc. Time-varying magnetic field stimulation of the median and ulnar nerves in the carpal region is studied, with special consideration of the influence of non-homogeneities.MethodsA detailed three-dimensional finite element model (FEM) of the anatomy of the wrist region was built to assess the induced currents distribution by external magnetic stimulation. The electromagnetic field distribution in the non-homogeneous domain was defined as an internal Dirichlet problem using the finite element method. The boundary conditions were obtained by analysis of the vector potential field excited by external current-driven coils.ResultsThe results include evaluation and graphical representation of the induced current field distribution at various stimulation coil positions. Comparative study for the real non-homogeneous structure with anisotropic conductivities of the tissues and a mock homogeneous media is also presented. The possibility of achieving selective stimulation of either of the two nerves is assessed.ConclusionThe model developed could be useful in theoretical prediction of the current distribution in the nerves during diagnostic stimulation and therapeutic procedures involving electromagnetic excitation. The errors in applying homogeneous domain modeling rather than real non-homogeneous biological structures are demonstrated. The practical implications of the applied approach are valid for any arbitrary weakly conductive medium.
Highlights
Peripheral nerves are situated in a highly non-homogeneous environment, including muscles, bones, blood vessels, etc
The induced current density (J) distribution depends on the electric field, and on the tissue specific resistivities
We should note that the image definition (Figs. 4,5,6,7) and the current profiles smoothness (Fig. 8) depend on the finite element mesh size used, which was restricted by the total number of elements in the model and their respective distribution (Fig. 2)
Summary
Peripheral nerves are situated in a highly non-homogeneous environment, including muscles, bones, blood vessels, etc. Time-varying magnetic field stimulation of the median and ulnar nerves in the carpal region is studied, with special consideration of the influence of nonhomogeneities. The analysis of electrical fields induced by magnetic stimulation has been addressed by many authors. Non-homogeneities do influence correct coil design, excitation current, and positioning with respect to stimulation sites. It is well known that excitation of peripheral nerves is achieved by electrical current or magnetically induced current, especially by the component parallel to the nerve, as ensuing from the well-known cable equation [1]:. The Jz component, only a fraction of the globally induced current field pattern, is associated with the properties of the conductive medium. The induced current density (J) distribution depends on the electric field, and on the tissue specific resistivities. Excitation will occur at sites where the local current density exceeds a certain threshold
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
