Dipole location errors in electroencephalogram source analysis due to volume conductor model errors

Abstract

An examination is made of dipole location errors in electroencephalogram (EEG) source analysis, due to not incorporating the ventricular system (VS), omitting a hole in the skull and underestimating skull conductivity. The simulations are performed for a large number of test dipoles in 3D using the finite difference method. The maximum dipole location error encountered, utilising 27 and 53 electrodes is 7.6 mm and 6.1 mm, respectively when omitting the VS, 5.6 mm and 5.2 mm, respectively when neglecting the hole in the skull, and 33.4 mm and 28.0 mm, respectively when underestimating skull conductivity. The largest location errors due to neglecting the VS can be found in the vicinity of the VS. The largest location errors due to omitting a hole can be found in the vicinity of the hole. At these positions the fitted dipoles are found close to the hole. When skull conductivity is underestimated, the dipole is fitted close to the skull-brain border in a radial direction for all test dipoles. It was found that the location errors due to underestimating skull conductivity are typically higher than those found due to neglecting the VS or neglecting a hole in the skull.

Influence of skull conductivity perturbations on EEG dipole source analysis

“…Several researchers investigated the dipole location error due to skull conductivity perturbation (Awada et al 1998, Pohlmeier et al 1997, Laarne et al 2000, and Vanrumste et al 2000. Awada et al (1998) used 2D finite element method.…”

“…Later on, Laarne et al (2000) found that the average dipole location error was about 7.5 mm and 6.5 mm when 19 electrode and 58 electrodes were used respectively. Vanrumste et al (2000) used a large number of test dipoles and a 3D volume conductor to investigate the dipole location error due to the higher skull conductivity of head model used in the forward problem than that in the inverse problem. They found that the location error of most test dipoles was between 5 mm and 20 mm, and the maximum errors were33.4 mm and 28.0 mm for 27 and 53 electrodes, respectively.…”

“…All the above studies evaluated only one single disturbance value: Awada et al (1998) set the skull conductivity value to be 3.3 times higher in the forward than that in the inverse problems, while Pohlmeier et al (1997), Laarne et al (2000), and Vanrumste et al (2000) set that value to 5. Furthermore, they didn't evaluate the influence of using lower skull conductivity in the forward problem than that in the inverse problem.…”

“…The potentials calculated at k electrodes at a single time instant can be represented by V in . For both the spherical and realistic head models, the dipole parameters ( , ) were estimated by minimizing the relative residual energy (RRE) (Vanrumste et al 2000):…”

Compensation of domain modelling errors in the inverse source problem of the Poisson equation: Application in electroencephalographic imaging

“…In EEG source problem, neural sources are reconstructed inside the brain based on electric potential measurements around the scalp, and it is well known that the inverse solution depends strongly on the accuracy of discretized head geometry [2,4,7,8,16,39,49,54] and the accuracy of electric conductivity modelling of different tissues [3,47,25,48,34,50,51]. The head features can be extracted, to some extent, by using multi-modal imaging (computed tomography / diffusion magnetic resonance imaging), for example.…”