Impact of Different Noise Sources on Dipole Localization in the Spherical Model: A Simulation

Abstract

In an effort to understand the impact of the different noise sources present in current multi-channel Neuromagnetometers® we have developed a set of modeling routines which allow us to independently add noise corresponding to these different sources to the forward solution for a current dipole in a homogeneous spherical conductor (Sarvas 1987). The resulting perturbed forward solution is then inverted using the nonlinear least squares fitting routine in the Biomagnetic Technologies Inc. (BTi) Neuromagnetometer software. Unlike several previous analysis of noise effects (Ribeiro et al. 1988, Kaukoranta et al. 1986) we were interested in simulating a number of different sources to look at each contribution independently and together. We have included field noise, relative gain error of a multi-channel system, translational error in placement of the system, and rotational error in placement of the system. We have measured the statistics of the resulting fits as an estimate of the noise introduced into the localization.