Factors limiting the application of electrical impedance tomography for identification of regional conductivity changes using scalp electrodes during epileptic seizures in humans
| Autor: | Alistair McEwan, Lorenzo Fabrizi, Richard Bayford, J. F. Perez-Juste Abascal, Lior Horesh, David Holder, R Elwes, Colin D. Binnie, M Sparkes |
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| Rok vydání: | 2006 |
| Předmět: |
Adult
Male medicine.medical_specialty Physiology Biomedical Engineering Biophysics Electroencephalography Sensitivity and Specificity Signal Epilepsy Neuroimaging Physiology (medical) Image Interpretation Computer-Assisted Electric Impedance Humans Medicine Plethysmography Impedance Electrodes Tomography Electrical impedance tomography Brain Mapping Scalp medicine.diagnostic_test business.industry Reproducibility of Results Limiting Middle Aged Image Enhancement medicine.disease medicine.anatomical_structure Female Neurosurgery business Algorithms Biomedical engineering |
| Zdroj: | Physiological Measurement. 27:S163-S174 |
| ISSN: | 1361-6579 0967-3334 |
| DOI: | 10.1088/0967-3334/27/5/s14 |
| Popis: | Electrical impedance tomography (EIT) has the potential to produce images during epileptic seizures. This might improve the accuracy of the localization of epileptic foci in patients undergoing presurgical assessment for curative neurosurgery. It has already been shown that impedance increases by up to 22% during induced epileptic seizures in animal models, using cortical or implanted electrodes in controlled experiments. The purpose of this study was to determine if reproducible raw impedance changes and EIT images could be collected during epileptic seizures in patients who were undergoing observation with video-electroencephalography (EEG) telemetry as part of evaluation prior to neurosurgery to resect the region of brain causing the epilepsy. A secondary purpose was to develop an objective method for processing and evaluating data, as seizures arose at unpredictable times from a noisy baseline. Four-terminal impedance measurements from 258 combinations were collected continuously using 32 EEG scalp electrodes in 22 seizure episodes from 7 patients during their presurgical assessment together with the standard EEG recordings. A reliable method for defining the pre-seizure baseline and recording impedance data and EIT images was developed, in which EIT and EEG could be acquired simultaneously after filtering of EIT artefact from the EEG signal. Fluctuations of several per cent over minutes were observed in the baseline between seizures. During seizures, boundary voltage changes diverged with a standard deviation of 1-54% from the baseline. No reproducible changes with the expected time course of some tens of seconds and magnitude of about 0.1% could be reliably measured. This demonstrates that it is feasible to acquire EIT images in parallel with standard EEG during presurgical assessment but, unfortunately, expected EIT changes on the scalp of about 0.1% are swamped by much larger movement and systematic artefact. Nevertheless, EIT has the unique potential to provide invaluable neuroimaging data for this purpose and may still become possible with improvements in electrode design and instrumentation. |
| Databáze: | OpenAIRE |
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