title: Accuracy of EEG dipole source localization using implanted sources in the human brain.
abstract: OBJECTIVE
  The location of electrical sources in the brain can be estimated by calculating inverse solutions in which the location, amplitude and orientation of the electrical sources are fitted to the scalp EEG. To assess localization accuracy of the moving dipole inverse solution algorithm (ISA), we studied two patients who had depth electrodes implanted for presurgical planning of epilepsy surgery.
  
  
  METHODS
  Artificial dipoles were created by connecting a single sine wave pulse generator to different pairs of electrodes in multiple orientations and depths. Surface EEG recordings of the resulting pulses were evaluated with the ISA using a 4-shell spherical head model and plotted on the subjects' MRI. Dipole localization errors were evaluated with respect to the number of averaged pulses, different electrode montages and different dipole locations and orientations.
  
  
  RESULTS
  Dipoles located at 40-57 mm from the scalp surface had localization errors that were greater than those located at 62-85 mm. Localization accuracy improved with increasing numbers of pulses and recording electrodes. Results with a standard 10-20 array of 21 electrodes showed an average localization error of 17 mm, whereas 41 electrodes improved this to 13 mm. Mean angular errors were 31 and 30 degrees, respectively.
  
  
  CONCLUSIONS
  The ISA was able to differentiate between tangential and radial dipoles. We conclude that our implementation of the ISA is a useful and sound method for localizing electrical activity in the brain.
authors.affiliation: Clinical Neurophysiology Laboratory of the Neurology Service, Massachusetts General Hospital, Boston 02114, USA.
authors.forename: T
authors.initials: T
authors.lastname: Krings
authors.forename: K H
authors.initials: KH
authors.lastname: Chiappa
authors.forename: B N
authors.initials: BN
authors.lastname: Cuffin
authors.forename: J I
authors.initials: JI
authors.lastname: Cochius
authors.forename: S
authors.initials: S
authors.lastname: Connolly
authors.forename: G R
authors.initials: GR
authors.lastname: Cosgrove
mesh_terms: D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology*; D006801:Humans