Beamforming applied to surface EEG improves ripple visibility

Arjen Mol, Nicole van Klink, Cyrille Ferrier, Arjan Hillebrand, Geertjan Huiskamp, Maeike Zijlmans

Research output: Scientific - peer-reviewArticle

Abstract

Objective Surface EEG can show epileptiform ripples in people with focal epilepsy, but identification is impeded by the low signal-to-noise ratio of the electrode recordings. We used beamformer-based virtual electrodes to improve ripple identification. Methods We analyzed ten minutes of interictal EEG of nine patients with refractory focal epilepsy. EEGs with more than 60 channels and 20 spikes were included. We computed ∼79 virtual electrodes using a scalar beamformer and marked ripples (80–250 Hz) co-occurring with spikes in physical and virtual electrodes. Ripple numbers in physical and virtual electrodes were compared, and sensitivity and specificity of ripples for the region of interest (ROI; based on clinical information) were determined. Results Five patients had ripples in the physical electrodes and eight in the virtual electrodes, with more ripples in virtual than in physical electrodes (101 vs. 57, p =.007). Ripples in virtual electrodes predicted the ROI better than physical electrodes (AUC 0.65 vs. 0.56, p =.03). Conclusions Beamforming increased ripple visibility in surface EEG. Virtual ripples predicted the ROI better than physical ripples, although sensitivity was still poor. Significance Beamforming can facilitate ripple identification in EEG. Ripple localization needs to be improved to enable its use for presurgical evaluation in people with epilepsy.

Original languageEnglish
Article number129
Pages (from-to)101-111
Number of pages11
JournalClinical Neurophysiology
Volume129
Issue number1
DOIs
StatePublished - 1 Jan 2018

Cite this

Mol, A., van Klink, N., Ferrier, C., Hillebrand, A., Huiskamp, G., & Zijlmans, M. (2018). Beamforming applied to surface EEG improves ripple visibility. Clinical Neurophysiology, 129(1), 101-111. [129]. DOI: 10.1016/j.clinph.2017.10.026

Mol, Arjen; van Klink, Nicole; Ferrier, Cyrille; Hillebrand, Arjan; Huiskamp, Geertjan; Zijlmans, Maeike / Beamforming applied to surface EEG improves ripple visibility.

In: Clinical Neurophysiology, Vol. 129, No. 1, 129, 01.01.2018, p. 101-111.

Research output: Scientific - peer-reviewArticle

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title = "Beamforming applied to surface EEG improves ripple visibility",
abstract = "Objective Surface EEG can show epileptiform ripples in people with focal epilepsy, but identification is impeded by the low signal-to-noise ratio of the electrode recordings. We used beamformer-based virtual electrodes to improve ripple identification. Methods We analyzed ten minutes of interictal EEG of nine patients with refractory focal epilepsy. EEGs with more than 60 channels and 20 spikes were included. We computed ∼79 virtual electrodes using a scalar beamformer and marked ripples (80–250 Hz) co-occurring with spikes in physical and virtual electrodes. Ripple numbers in physical and virtual electrodes were compared, and sensitivity and specificity of ripples for the region of interest (ROI; based on clinical information) were determined. Results Five patients had ripples in the physical electrodes and eight in the virtual electrodes, with more ripples in virtual than in physical electrodes (101 vs. 57, p =.007). Ripples in virtual electrodes predicted the ROI better than physical electrodes (AUC 0.65 vs. 0.56, p =.03). Conclusions Beamforming increased ripple visibility in surface EEG. Virtual ripples predicted the ROI better than physical ripples, although sensitivity was still poor. Significance Beamforming can facilitate ripple identification in EEG. Ripple localization needs to be improved to enable its use for presurgical evaluation in people with epilepsy.",
keywords = "Beamforming, Electroencephalography, Epilepsy, High frequency oscillations, Virtual electrodes",
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Mol, A, van Klink, N, Ferrier, C, Hillebrand, A, Huiskamp, G & Zijlmans, M 2018, 'Beamforming applied to surface EEG improves ripple visibility' Clinical Neurophysiology, vol 129, no. 1, 129, pp. 101-111. DOI: 10.1016/j.clinph.2017.10.026

Beamforming applied to surface EEG improves ripple visibility. / Mol, Arjen; van Klink, Nicole; Ferrier, Cyrille; Hillebrand, Arjan; Huiskamp, Geertjan; Zijlmans, Maeike.

In: Clinical Neurophysiology, Vol. 129, No. 1, 129, 01.01.2018, p. 101-111.

Research output: Scientific - peer-reviewArticle

TY - JOUR

T1 - Beamforming applied to surface EEG improves ripple visibility

AU - Mol,Arjen

AU - van Klink,Nicole

AU - Ferrier,Cyrille

AU - Hillebrand,Arjan

AU - Huiskamp,Geertjan

AU - Zijlmans,Maeike

PY - 2018/1/1

Y1 - 2018/1/1

N2 - Objective Surface EEG can show epileptiform ripples in people with focal epilepsy, but identification is impeded by the low signal-to-noise ratio of the electrode recordings. We used beamformer-based virtual electrodes to improve ripple identification. Methods We analyzed ten minutes of interictal EEG of nine patients with refractory focal epilepsy. EEGs with more than 60 channels and 20 spikes were included. We computed ∼79 virtual electrodes using a scalar beamformer and marked ripples (80–250 Hz) co-occurring with spikes in physical and virtual electrodes. Ripple numbers in physical and virtual electrodes were compared, and sensitivity and specificity of ripples for the region of interest (ROI; based on clinical information) were determined. Results Five patients had ripples in the physical electrodes and eight in the virtual electrodes, with more ripples in virtual than in physical electrodes (101 vs. 57, p =.007). Ripples in virtual electrodes predicted the ROI better than physical electrodes (AUC 0.65 vs. 0.56, p =.03). Conclusions Beamforming increased ripple visibility in surface EEG. Virtual ripples predicted the ROI better than physical ripples, although sensitivity was still poor. Significance Beamforming can facilitate ripple identification in EEG. Ripple localization needs to be improved to enable its use for presurgical evaluation in people with epilepsy.

AB - Objective Surface EEG can show epileptiform ripples in people with focal epilepsy, but identification is impeded by the low signal-to-noise ratio of the electrode recordings. We used beamformer-based virtual electrodes to improve ripple identification. Methods We analyzed ten minutes of interictal EEG of nine patients with refractory focal epilepsy. EEGs with more than 60 channels and 20 spikes were included. We computed ∼79 virtual electrodes using a scalar beamformer and marked ripples (80–250 Hz) co-occurring with spikes in physical and virtual electrodes. Ripple numbers in physical and virtual electrodes were compared, and sensitivity and specificity of ripples for the region of interest (ROI; based on clinical information) were determined. Results Five patients had ripples in the physical electrodes and eight in the virtual electrodes, with more ripples in virtual than in physical electrodes (101 vs. 57, p =.007). Ripples in virtual electrodes predicted the ROI better than physical electrodes (AUC 0.65 vs. 0.56, p =.03). Conclusions Beamforming increased ripple visibility in surface EEG. Virtual ripples predicted the ROI better than physical ripples, although sensitivity was still poor. Significance Beamforming can facilitate ripple identification in EEG. Ripple localization needs to be improved to enable its use for presurgical evaluation in people with epilepsy.

KW - Beamforming

KW - Electroencephalography

KW - Epilepsy

KW - High frequency oscillations

KW - Virtual electrodes

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Mol A, van Klink N, Ferrier C, Hillebrand A, Huiskamp G, Zijlmans M. Beamforming applied to surface EEG improves ripple visibility. Clinical Neurophysiology. 2018 Jan 1;129(1):101-111. 129. Available from, DOI: 10.1016/j.clinph.2017.10.026