Distributed Current Source Method for Modeling Magnetic and Eddy-Current Fields induced in Biological Object

This paper presents a distributed current source method for modeling weak magnetic and eddy-current (EC) fields induced in biological objects for electromagnetic stimulation and sensing applications. Unlike metallic objects with negligible displacement currents, the permittivity must be accounted for in biological objects. An axial symmetrical 2D EC field induced in a biological object is formulated in state space representation. Since EC fields cannot be directly measured, the solutions to three different variables that provide a means to infer the EC effects are derived using the distributed current source method, which are the magnetic flux density generated by the induced EC at a point, the lumped-parameter magnetic flux passing through a sensing coil, and its electromotive force. Illustrated in the context of two applications, the solutions are numerically evaluated by comparing results with that simulated by a commercial finite-element analysis.