On the magnetic field generated outside an inhomogeneous volume conductor by internal current sources

The magnetocardiogram results from the detection of magnetic fields generated outside the body by electric current sources in the heart. Let the source current dipole moment per unit volume be Jⁱ, the conductivity , the electric potential , and the electric field intensity . Then it may be shown that the magnetic field is given by either , or , where the surface integral is over all surfaces Siseparating regions of different conductivity, i.e., \´ and ", and is the distance from the point of measurement to the element of volume or surface. The magnetic dipole moment is given by , where r1is a radius vector from an arbitrary origin.