Bayesian Modelling of Skull Conductivity Uncertainties in EEG Source Imaging

Incorporating and compensating cerebrospinal fluid in surface-based forward models of magneto– and electroencephalography

10.1101/037788 ◽

2016 ◽

Author(s):

Matti Stenroos ◽

Aapo Nummenmaa

Keyword(s):

Cerebrospinal Fluid ◽

Relative Error ◽

Reference Model ◽

Head Model ◽

Computationally Efficient ◽

Source Imaging ◽

Test Models ◽

Eeg Source Imaging ◽

Skull Conductivity ◽

S Model

AbstractMEG/EEG source imaging is usually done using a three-shell (3-S) or a simpler head model. Such models omit cerebrospinal fluid (CSF) that strongly affects the volume currents. We present a four-compartment (4-C) boundary-element (BEM) model that incorporates the CSF and is computationally efficient and straightforward to build using freely available software. We propose a way for compensating the omission of CSF by decreasing the skull conductivity of the 3-S model, and study the robustness of the 4-C and 3-S models to errors in skull conductivity.We generated dense boundary meshes using MRI datasets and automated SimNIBS pipeline. Then, we built a dense 4-C reference model using Galerkin BEM, and 4-C and 3-S test models using coarser meshes and both Galerkin and collocation BEMs. We compared field topographies of cortical sources, applying various skull conductivities and fitting conductivities that minimized the relative error in 4-C and 3-S models. When the CSF was left out from the EEG model, our compensated, unbiased approach improved the accuracy of the 3-S model considerably compared to the conventional approach, where CSF is neglected without any compensation (mean relative error < 20% vs. > 40%). The error due to the omission of CSF was of the same order in MEG and compensated EEG. EEG has, however, large overall error due to uncertain skull conductivity.Our results show that a realistic 4-C MEG/EEG model can be implemented using standard tools and basic BEM, without excessive workload or computational burden. If the CSF is omitted, compensated skull conductivity should be used in EEG.

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Faculty Opinions recommendation of Automated EEG source imaging: A retrospective, blinded clinical validation study.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.734143825.793565898 ◽

2019 ◽

Author(s):

Christoph Baumgartner

Keyword(s):

Validation Study ◽

Clinical Validation ◽

Source Imaging ◽

Eeg Source Imaging

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EEG Source Imaging (ESI) utility in clinical practice

Biomedical Engineering / Biomedizinische Technik ◽

10.1515/bmt-2019-0128 ◽

2020 ◽

Vol 65 (6) ◽

pp. 673-682

Author(s):

Pegah Khosropanah ◽

Eric Tatt-Wei Ho ◽

Kheng-Seang Lim ◽

Si-Lei Fong ◽

Minh-An Thuy Le ◽

...

Keyword(s):

Focal Epilepsy ◽

Cost Effective ◽

Head Model ◽

Computational Technique ◽

Epileptogenic Zone ◽

Clinical Tool ◽

Source Imaging ◽

Localization Accuracy ◽

Eeg Source Imaging ◽

Surgical Evaluation

AbstractEpilepsy surgery is an important treatment modality for medically refractory focal epilepsy. The outcome of surgery usually depends on the localization accuracy of the epileptogenic zone (EZ) during pre-surgical evaluation. Good localization can be achieved with various electrophysiological and neuroimaging approaches. However, each approach has its own merits and limitations. Electroencephalography (EEG) Source Imaging (ESI) is an emerging model-based computational technique to localize cortical sources of electrical activity within the brain volume, three-dimensionally. ESI based pre-surgical evaluation gives an overall clinical yield of 73–91%, depending on choice of head model, inverse solution and EEG electrode density. It is a cost effective, non-invasive method which provides valuable additional information in presurgical evaluation due to its high localizing value specifically in MRI-negative cases, extra or basal temporal lobe epilepsy, multifocal lesions such as tuberous sclerosis or cases with multiple hypotheses. Unfortunately, less than 1% of surgical centers in developing countries use this method as a part of pre-surgical evaluation. This review promotes ESI as a useful clinical tool especially for patients with lesion-negative MRI to determine EZ cost-effectively with high accuracy under the optimized conditions.

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ConvDip: A convolutional neural network for better M/EEG Source Imaging

10.1101/2020.04.09.033506 ◽

2020 ◽

Cited By ~ 2

Author(s):

Lukas Hecker ◽

Rebekka Rupprecht ◽

Ludger Tebartz van Elst ◽

Juergen Kornmeier

Keyword(s):

Neural Network ◽

Inverse Problem ◽

Convolutional Neural Network ◽

Brain Activity ◽

Clinical Diagnostics ◽

Dipole Model ◽

Source Imaging ◽

Eeg Source Imaging ◽

Eeg Data ◽

Inverse Solutions

AbstractEEG and MEG are well-established non-invasive methods in neuroscientific research and clinical diagnostics. Both methods provide a high temporal but low spatial resolution of brain activity. In order to gain insight about the spatial dynamics of the M/EEG one has to solve the inverse problem, which means that more than one configuration of neural sources can evoke one and the same distribution of EEG activity on the scalp. Artificial neural networks have been previously used successfully to find either one or two dipoles sources. These approaches, however, have never solved the inverse problem in a distributed dipole model with more than two dipole sources. We present ConvDip, a novel convolutional neural network (CNN) architecture that solves the EEG inverse problem in a distributed dipole model based on simulated EEG data. We show that (1) ConvDip learned to produce inverse solutions from a single time point of EEG data and (2) outperforms state-of-the-art methods (eLORETA and LCMV beamforming) on all focused performance measures. (3) It is more flexible when dealing with varying number of sources, produces less ghost sources and misses less real sources than the comparison methods. (4) It produces plausible inverse solutions for real-world EEG recordings and needs less than 40 ms for a single forward pass. Our results qualify ConvDip as an efficient and easy-to-apply novel method for source localization in EEG and MEG data, with high relevance for clinical applications, e.g. in epileptology and real time applications.

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Influence of Patient-Specific Head Modeling on EEG Source Imaging

Computational and Mathematical Methods in Medicine ◽

10.1155/2020/5076865 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Yohan Céspedes-Villar ◽

Juan David Martinez-Vargas ◽

G. Castellanos-Dominguez

Keyword(s):

Neurological Diseases ◽

Structural Data ◽

Problem Formulation ◽

Patient Specific ◽

Source Imaging ◽

Eeg Source Imaging ◽

Deep Sources ◽

The Individual ◽

Tissue Compartments ◽

The Brain

Electromagnetic source imaging (ESI) techniques have become one of the most common alternatives for understanding cognitive processes in the human brain and for guiding possible therapies for neurological diseases. However, ESI accuracy strongly depends on the forward model capabilities to accurately describe the subject’s head anatomy from the available structural data. Attempting to improve the ESI performance, we enhance the brain structure model within the individual-defined forward problem formulation, combining the head geometry complexity of the modeled tissue compartments and the prior knowledge of the brain tissue morphology. We validate the proposed methodology using 25 subjects, from which a set of magnetic-resonance imaging scans is acquired, extracting the anatomical priors and an electroencephalography signal set needed for validating the ESI scenarios. Obtained results confirm that incorporating patient-specific head models enhances the performed accuracy and improves the localization of focal and deep sources.

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