SOURCE LOCALIZATION OF AVERAGED AND SINGLE EEG SPIKES USING THE ELECTRIC-DIPOLE MODEL

A scheme for localizing the epileptic focus is proposed. The scheme is on the basis of a model with an electric dipole inside a four-layer i nhomogeneous spherical model of head and utilizes a nonlinear programm ing algorithm applying the gradient projection method. Various initial estimates are used to prove the stability of the implemented dipole m odel. Fourteen single spike data and the averaged spike data are used to localize the epileptic focus. The results of the usage of the avera ged spike data show that the dipole position is compatible with visual inspection of experienced clinical physicians. The results of the usa ge of the single spike show that 11 of the 14 single spikes have dipol e locations near the result of the averaged spike but the estimated di pole moments differ markedly from one another. The localization result s of the other three single spikes show that the dipole position is st rongly affected by the background EEG. This kind of interference gener ally causes the eccentricity of the dipole to deviate from its anatomi cally meaningful value. According to our results, the electric dipole model is concluded to be valuable for the clinical application of loca lizing epileptic foci.