B. Yvert et al., IMPROVED DIPOLE LOCALIZATION USING LOCAL MESH REFINEMENT OF REALISTICHEAD GEOMETRIES - AN EEG SIMULATION STUDY, Electroencephalography and clinical neurophysiology, 99(1), 1996, pp. 79-89
A systematic evaluation of dipole localization accuracy using the boun
dary element method is presented. EEG simulations are carried out with
dipoles located in the right parietal and temporal regions of the hea
d. Uniformly meshed and locally refined head models are considered in
both spherical and realistic geometries. An initial study determines t
he influence upon the localization accuracy of the dipole depth below
the brain surface, of its orientation (radial and tangential), and of
the global and local mesh densities. Simulated potential data are comp
uted analytically in the spherical case, and numerically using a very
fine (locally refined) model in the realistic case. Results in both ge
ometries show that in order to get localization errors of about 2-4 mm
, uniformly meshed models may be used for dipoles located at depths gr
eater than 20 mm, whereas locally refined models should be used for sh
allower dipoles. Two other studies show how the localization accuracy
depends upon the size of the local refinement area and upon the number
of electrodes (19, 32, 63). Results show that a large number of elect
rodes brings significant improvements, especially for shallow and tang
ential dipoles.