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. 2009:2009:2930-3.
doi: 10.1109/IEMBS.2009.5333992.

Patch-basis electrocortical source imaging in epilepsy

Zeynep Akalin Acar  1 , Gregory Worrell, Scott Makeig
Affiliations

Patch-basis electrocortical source imaging in epilepsy

Zeynep Akalin Acar et al. Annu Int Conf IEEE Eng Med Biol Soc. 2009.

Abstract

In this study, we developed numerical methods for investigating the sources of epileptic activity from intracranial EEG recordings acquired from intracranial subdural electrodes (iEEG) in patients undergoing pre-surgical evaluation at the epilepsy center of the Mayo Clinic (Rochester, MN). The data were analyzed using independent component analysis (ICA), which identifies and isolates maximally independent signal components in multi-channel recordings. A realistic individual head model was constructed for a patient undergoing pre-surgical evaluation. Structural models of gray matter, white matter, CSF, skull, and scalp were extracted from pre-surgical MR and post-surgical CT images. The electromagnetic source localization forward problem was solved using the Boundary Element Method (BEM). Source localization was performed using the Sparse Bayesian Learning (SBL) algorithm. The multiscale patch-basis source space constructed for this purpose includes a large number of dipole elements on the cortical layer oriented perpendicular to the local cortical surface. These source dipoles are combined into overlapping multi-scalepatches. Using this approach, we were able to detect seizure activity on sulcal walls and on gyrus of the cortex.

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Figures

Fig. 1
Fig. 1
BEM model of the scalp, skull and the plastic sheet, represented by 10,000, 30,000, and 7,000 faces, respectively. (a) Skull and electrode sheet faces, (b) scalp, skull and sheet faces, (c) plastic sheet model of the plastic grid and strip electrode matrices.
Fig. 2
Fig. 2
CT image of the implanted grid electrodes. The two grids (6 × 8, 4 ×6) and one medial strip (1 ×8) implanted in the patient for clinical monitoring purposes.
Fig. 3
Fig. 3
Potential maps of two IC processes projected on the brain (a) and (b), and on the intracranial electrodes (c) and (d). Warm-color potentials represent positive values and cool colors, negative values (green represents 0). Multiplying these maps by the (two-sided) IC time courses gives the activity at each channel associated with the IC source.
Fig. 4
Fig. 4
Three Gaussian patches in different scales with radius (a) 10 mm, (b) 6 mm, and (c) 3 mm.
Fig. 5
Fig. 5
Inverse problem results for the two ICs shown in Figure 3. Red and blue (not seen here) indicate activity with opposite signs, green indicates no activity
See this image and copyright information in PMC

References

    1. Assaf BA, Ebersole JS. Continu ous Source Imaging of Scalp Ictal Rhythms in Temporal lobe epilepsy. Epilepsia. 1997;38(10):1114–1123. - PubMed
    1. Zhang Y, Ding L, van Drongelen W, Hecox K, Frim DM, He B. A cortical potential imaging study from simultaneous extra-and intracranial electrical recordings by means of the finite element method. NeuroImage. 2006;31:1513–1524. - PMC - PubMed
    1. Akalin Acar Z, Gencer NG. An advanced BEM implementation for the forward problem of Electro-magnetic source imaging. Physics in Med and Biol. 2004;49(5):5011–28. - PubMed
    1. Gencer NG, Akalin Acar Z. Use of the isolated problem approach for multi- compartment BEM models of electro-magnetic source imaging. Physics in Med and Biol. 2005;50:3007–22. - PubMed
    1. Ebersole JS, Hawes-Ebersole S. Clinical application of dipole models in the localization of epileptiform activity. J Clinical Neurophysiology. 2007;24(2):120–129. - PubMed

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