In vivo measurement of the brain and skull resistivities using an EIT-based method and the combined analysis of SEF/SEP data

Results of "in vivo" measurements of the skull and brain resistivities are presented for six subjects. Results are obtained using two different methods, based on spherical head models. The first method uses the principles of electrical impedance tomography (EIT) to estimate the equivalent...

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Bibliographic Details
Published in:IEEE transactions on biomedical engineering 2003-09, Vol.50 (9), p.1124-1127
Main Authors: Goncalve, S., de Munck, J.C., Verbunt, J.P.A., Heethaar, R.M., da Silva, F.H.L.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Brain - physiology
Brain Mapping - methods
Conductivity
Electric Impedance
Electric resistance
Electroencephalography
Electroencephalography - methods
Evoked Potentials, Somatosensory - physiology
Head - physiology
Impedance
In vivo
Magnetic heads
Medical sciences
Models, Biological
Parameter estimation
Reproducibility of Results
Sensitivity and Specificity
Skin
Skin Physiological Phenomena
Skull
Skull - physiology
Tomography
Tomography - methods
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Summary:Results of "in vivo" measurements of the skull and brain resistivities are presented for six subjects. Results are obtained using two different methods, based on spherical head models. The first method uses the principles of electrical impedance tomography (EIT) to estimate the equivalent electrical resistivities of brain (ρ/sub brain/), skull (ρ/sub skull/) and skin (ρ/sub skin/) according to S. Goncalves et al., Physiol. Meas., vol. 21, p. 379-93 (2000).. The second one estimates the same parameters through a combined analysis of the evoked somatosensory cortical response, recorded simultaneously using magnetoencephalography (MEG) and electroencephalography (EEG). The EIT results, obtained with the same relative skull thickness (0.05) for all subjects, show a wide variation of the ratio ρ/sub skull//ρ/sub brain/ among subjects (average =72, SD=48%). However, the ρ/sub skull//ρ/sub brain/ ratios of the individual subjects are well reproduced by combined analysis of somatosensory evoked fields (SEF) and somatosensory evoked potentials (SEP). These preliminary results suggest that the ρ/sub skull//ρ/sub brain/ variations over subjects cannot be disregarded in the EEG inverse problem (IP) when a spherical model is used. The agreement between EIT and SEF/SEP points to the fact that whatever the source of variability, the proposed EIT-based method
ISSN:0018-9294
1558-2531
DOI:10.1109/TBME.2003.816072