Dipole‐Source Analysis in a Realistic Head Model in Patients with Focal Epilepsy

Herrendorf, Gregor; Steinhoff, Bernhard J.; Kolle, Renate; Baudewig, Jürgen; Waberski, Till Dino; Büchner, Helmut; Paulus, Walter

doi:10.1111/j.1528-1157.2000.tb01508.x

Cited by 48 publications

(22 citation statements)

References 31 publications

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“…This is compared to a localization accuracy of 17 mm for MEG measurements of artificial dipoles generated from implanted subdural strips [Balish et al, 1991]. Other studies have estimated accuracy by comparing lesion data (e.g., tumor, epileptogenic focus) in epileptic patients with the non-invasive location estimates from EEG [Diekmann et al, 1998;Herrendorf et al, 2000;Ko et al, 1998;Krings et al, 1998;Nakasato et al, 1994] or MEG [Diekmann et al, 1998;Ko et al, 1998;Mikuni et al, 1997;Nakasato et al, 1994;Sutherling et al, 1987Sutherling et al, , 1988aStefan et al, 1994;Tiihonen et al, 1990]. Similar to the results of the artificial current dipoles, the EEG and MEG accuracy were comparable (ranging from 10 -20 mm).…”

Section: Introductionmentioning

confidence: 54%

Monte Carlo simulation studies of EEG and MEG localization accuracy

Liu¹,

Dale²,

Belliveau³

2002

Human Brain Mapping

330

256

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Both electroencephalography (EEG) and magnetoencephalography (MEG) are currently used to localize brain activity. The accuracy of source localization depends on numerous factors, including the specific inverse approach and source model, fundamental differences in EEG and MEG data, and the accuracy of the volume conductor model of the head (i.e., the forward model). Using Monte Carlo simulations, this study removes the effect of forward model errors and theoretically compares the use of EEG alone, MEG alone, and combined EEG/MEG data sets for source localization. Here, we use a linear estimation inverse approach with a distributed source model and a realistic forward head model. We evaluated its accuracy using the crosstalk and point spread metrics. The crosstalk metric for a specified location on the cortex describes the amount of activity incorrectly localized onto that location from other locations. The point spread metric provides the complementary measure: for that same location, the point spread describes the mis-localization of activity from that specified location to other locations in the brain. We also propose and examine the utility of a "noise sensitivity normalized" inverse operator. Given our particular forward and inverse models, our results show that 1) surprisingly, EEG localization is more accurate than MEG localization for the same number of sensors averaged over many source locations and orientations; 2) as expected, combining EEG with MEG produces the best accuracy for the same total number of sensors; 3) the noise sensitivity normalized inverse operator improves the spatial resolution relative to the standard linear estimation operator; and 4) use of an a priori fMRI constraint universally reduces both crosstalk and point spread. Hum. Brain Mapping 16:47-62, 2002.

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Section: Introductionmentioning

confidence: 54%

Monte Carlo simulation studies of EEG and MEG localization accuracy

Liu¹,

Dale²,

Belliveau³

2002

Human Brain Mapping

330

256

View full text Add to dashboard Cite

show abstract

“…As previously shown, SMDM solution tends to localize closer at the temporal lobe with a realistically shaped head model such as BEM in comparison to the application of an idealized spherical head model (16,18,19,22). In spherical models, solutions show a systematic error towards a higher localization within the upper temporal or lower frontal lobe.…”

Section: Discussionmentioning

confidence: 66%

“…Although it is evident that the application of individual realistically shaped head models leads to a more precise localization of temporal epileptiform activity in single dipole solutions (16,18,19,22), it has yet to be evaluated to what extent the implementation of advanced source reconstruction methods such as CDR improves source reconstruction in this application.…”

Section: Introductionmentioning

confidence: 99%

Source Reconstruction of Mesial‐Temporal Epileptiform Activity: Comparison of Inverse Techniques

2000

Epilepsia

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Summary:Purpose: To evaluate whether advanced source reconstruction such as current density reconstruction (CDR) provides additional hints for clinical presurgical evaluation, different source reconstruction techniques with idealized spherical as well as realistically shaped head models (boundary element method, BEM) were applied on interictal and ictal epileptiform activity in presurgical evaluated patients with temporal lobe epilepsy. It is discussed whether CDR and BEM give additional information for presurgical evaluation compared to "conventional" strategies, such as single moving, and spatio-temporal dipole modeling with spherical head models.Methods: A variety of source reconstruction procedures were applied to the data of five patients with pharmacoresistent temporal lobe epilepsy with probable mesial origin: (1) singlemoving dipole in a spherical head model and (2) in BEM, (3) spatio-temporal dipole modeling in a spherical head model and (4) in BEM; and (5) deconvolution with fixed locations and orientations and (6) with cortically constrained L1-norm CDR in BEM. In addition, simulated sources of temporal lobe origin were calculated in each subject with CDR to prove the basic feasibility of this technique in the particular application.Results: Source activity was correctly localized within the affected temporal lobe by all source reconstruction techniques used. Neither single moving dipole, spatio-temporal modeling, nor CDR was able to localize sources at a sublobar level. In the case of two sources, single moving dipole solutions showed changes in dipole orientation in time and spatio-temporal modeling separated two sources, whereas CDR at the peak latency failed to distinguish among different origins. BEM enhanced localization accuracy.Conclusion: There was no advantage of using CDR. Single moving dipole as well as spatio-temporal dipole modeling in BEM leads to more precise localization within the individual anatomy and provides a simple algorithm, which is capable of indicating both the time course and the number of sources.

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“…Brain-shaped models which allow for individual modeling of head and brain geometry as well as conductivity are computationally more elaborate, as there exist no analytic solutions and numerical techniques, i.e., finite difference or finite element models have to be applied. These latter models, however, provide more accurate solutions [24,25,26,27,28].…”

Section: Source Modeling Of Meg Datamentioning

confidence: 94%

Magnetoencephalography in presurgical epilepsy evaluation

et al. 2002

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The introduction of whole-head magnetoencephalography (MEG) systems facilitating simultaneous recording from the entire brain surface has led to a major breakthrough of MEG in presurgical epilepsy evaluation. Localizations of the interictal spike zone with MEG showed excellent agreement with invasive electrical recordings, were useful to clarify the spatial relationship of the irritative spike zone to structural lesions, and could attribute epileptic activity to lobar subcompartments both in temporal lobe and extratemporal epilepsy. MEG was especially useful for the study of patients with non-lesional neocortical epilepsy and of patients with large lesions, where it provided unique information on the epileptogenic zone. It could reliably localize sensorimotor cortex prior to surgical procedures adjacent to central fissure. MEG language mapping yielded concordant results with the Wada test and cortical stimulation studies. MEG localizations of epileptic activity and essential brain regions were successfully integrated into frameless stereotaxy systems providing accurate functional information intraoperatively. Because MEG and EEG yield both complementary and confirmatory information, combined MEG-EEG recordings in conjunction with advanced source modeling techniques will further improve the noninvasive evaluation of epilepsy patients and constantly reduce the need for invasive procedures.

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Dipole‐Source Analysis in a Realistic Head Model in Patients with Focal Epilepsy

Cited by 48 publications

References 31 publications

Monte Carlo simulation studies of EEG and MEG localization accuracy

Monte Carlo simulation studies of EEG and MEG localization accuracy

Source Reconstruction of Mesial‐Temporal Epileptiform Activity: Comparison of Inverse Techniques

Magnetoencephalography in presurgical epilepsy evaluation

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