An evaluation of dipole reconstruction accuracy with spherical and realistic head models in MEG

MEG forward problem has been solved for about 2000 dipoles placed on the br ain surface using a very fine 3-layer realistic model of the head and the b oundary element method (BEM). For each dipole, spherical models, one-layer realistic BEM models and coarser 3-layer realistic BEM models, were used to reconstruct the dipole. It was found that the localization bias induced by using a spherical model of the head increased from 2.5 mm in the upper par t of the head to 12 mm in the lower part, on average. It was also found tha t, for the same computing time, a 3-layer model of the head gave on average 2 mm better localization errors than a one-layer model of the head. Orient ation errors of less than 20 degrees could only be retrieved with a 3-layer realistic model. Localization and orientation errors highly depended on th e dipole position in the brain. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.