A Method to Estimate the Condition of the Path of a Nerve by Measuring Neural Generation of Magnetic Fields

Abstract

The behavior of peripheral nerves is worth measuring not only to understand our nervous system, but also to diagnose various neural malfunctions. SQUID seems to provide a new noninvasive method to monitor the activity or condition of peripheral nerves by measuring magnetic fields. This method seems to have an advantage of depth positioning of current sources over measuring the skin potential. However, hitherto there are only a few reports that describe experimental researches on magnetic fields induced by peripheral nerves. As a model of the electric current sources that propagate along a peripheral nerve, a pair of current dipoles back to back is suggested, however, it seems there is no theoretical model that supports this hypothesis. Therefore, a study on a method to estimate two current dipoles from a distribution of magnetic field was carried out. The preceding experimental studies on measuring magnetic fields from peripheral nerves are concerned only to the normal component of the field, however measuring tangential component of the field is helpful to estimate the moments of dipoles and the path of a nerve. Therefore here, a procedure to estimate a pair of dipoles from a distribution of both normal and tangential component of a magnetic field is described.