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Imaging of focal seizures with Electrical Impedance Tomography and depth electrodes in real time

Witkowska-Wrobel, A; Aristovich, K; Crawford, A; Perkins, JD; Holder, D; (2021) Imaging of focal seizures with Electrical Impedance Tomography and depth electrodes in real time. NeuroImage , 234 , Article 117972. 10.1016/j.neuroimage.2021.117972. (In press). Green open access

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Abstract

Intracranial EEG is the current gold standard technique for localising seizures for surgery, but it can be insensitive to tangential dipole or distant sources. Electrical Impedance Tomography (EIT) offers a novel method to improve coverage and seizure onset localisation. The feasibility of EIT has been previously assessed in a computer simulation, which revealed an improved accuracy of seizure detection with EIT compared to intracranial EEG. In this study, slow impedance changes, evoked by cell swelling occurring over seconds, were reconstructed in real time by frequency division multiplexing EIT using depth and subdural electrodes in a swine model of epilepsy. EIT allowed to generate repetitive images of ictal events at similar time course to fMRI but without its significant limitations. EIT was recorded with a system consisting of 32 parallel current sources and 64 voltage recorders. Seizures triggered with intracranial injection of benzylpenicillin (BPN) in five pigs caused a repetitive peak impedance increase of 3.4±1.5 mV and 9.5±3% (N=205 seizures); the impedance signal change was seen already after a single, first seizure. EIT enabled reconstruction of the seizure onset 9±1.5 mm from the BPN cannula and 7.5±1.1 mm from the closest SEEG contact (p<0.05, n=37 focal seizures in three pigs) and it could address problems with sampling error in intracranial EEG. The amplitude of the impedance change correlated with the spread of the seizure on the SEEG (p <0.001, n=37). The results presented here suggest that combining a parallel EIT system with intracranial EEG monitoring has a potential to improve the diagnostic yield in epileptic patients and become a vital tool in improving our understanding of epilepsy.

Type: Article
Title: Imaging of focal seizures with Electrical Impedance Tomography and depth electrodes in real time
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.neuroimage.2021.117972
Publisher version: http://dx.doi.org/10.1016/j.neuroimage.2021.117972
Language: English
Additional information: © 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Keywords: EIT, Epilepsy, Intracranial electrodes, Seizure Imaging, Seizure model
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10125436
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