Volume currents in biomagnetic imaging

William J. Dallas

doi:10.1117/12.18777

1 July 1990 Volume currents in biomagnetic imaging

William J. Dallas

Proceedings Volume 1231, Medical Imaging IV: Image Formation; (1990) https://doi.org/10.1117/12.18777
Event: Medical Imaging '90, 1990, Newport Beach, CA, United States

Abstract

In biomagnetic imaging, the magnetic field caused by electrical nerve impulses is measured and used to form an estimate of the location and strength of the impulse. One complicating factor in forming this estimate is the fact that the impulses induce current flow in the volume conductor surrounding the nerve.17 In this presentation we explore the properties of these volume currents. We first formulate the problem in the standard form using Ohm's law to relate the volume current to the impressed (nerve impulse) current and the conductivity distribution. We then depart from the usual derivation by making use of properties of the fourier-transformed maxwell8 and continuity equations. In fourier space, the divergence operation in a vector field becomes a simple taking of the radial component of the fourier-transformed field; the curl transforms into taking tangential components. By decomposing the current densities and using the maxwell equations, we are able to arrive at a recursive differential expression for the volume-current generated magnetic field. The driving term in the expression is the current due to the divergence of the impressed current density. We provide some examples of applying this expression to simply shaped conductors.

Citation Download Citation

William J. Dallas "Volume currents in biomagnetic imaging", Proc. SPIE 1231, Medical Imaging IV: Image Formation, (1 July 1990); https://doi.org/10.1117/12.18777

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