Abstract
A method is described which estimates the location of current dipoles in the brain. The estimate establishes the best fit, according to stated criteria, between observed magnetic fields measured with a third-order gradiometer and fields predicted from one or two dipoles. The method takes into account corrections for the number, spatial separation and size of the gradiometer coils, and for the inclination of the axis of the gradiometer to the radius from a computed origin in the head to the centre of the sensing (first) coil, or to the position of observation on the head. The method also provides for a means to establish the best initial guess for a dipole location and contains procedures for estimating the positions of more than two dipoles in appropriate cases. Several relevant theoretical considerations are discussed and a number of applications of the method are described.