Contact Pressure and Flexibility of Multipin Dry EEG Electrodes

Fiedler, Patrique; Muhle, Richard; Griebel, Stefan; Pedrosa, Paulo; Fonseca, C.; Vaz, F.; Zanow, F.; Haueisen, Jens

doi:10.1109/tnsre.2018.2811752

Cited by 68 publications

(67 citation statements)

References 33 publications

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“…(2020) 10:5218 | https://doi.org/10.1038/s41598-020-62154-0www.nature.com/scientificreports www.nature.com/scientificreports/ by the aforementioned criteria and omitting the high pass and notch filtering mentioned above. Absolute spectral band power values were computed for the following frequency bands, which are typically reported in clinical EEG settings: Delta (1.5-4 Hz), Theta (4-8 Hz), Alpha (8-13 Hz), Beta(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30).…”

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confidence: 99%

Comparison between a wireless dry electrode EEG system with a conventional wired wet electrode EEG system for clinical applications

Hinrichs

Scholz

Baum

et al. 2020

Sci Rep

138

101

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Dry electrode electroencephalogram (EEG) recording combined with wireless data transmission offers an alternative tool to conventional wet electrode EEG systems. However, the question remains whether the signal quality of dry electrode recordings is comparable to wet electrode recordings in the clinical context. We recorded the resting state EEG (rsEEG), the visual evoked potentials (VEP) and the visual P300 (P3) from 16 healthy subjects (age range: 26-79 years) and 16 neurological patients who reported subjective memory impairment (age range: 50-83 years). Each subject took part in two recordings on different days, one with 19 dry electrodes and another with 19 wet electrodes. They reported their preferred EEG system. Comparisons of the rsEEG recordings were conducted qualitatively by independent visual evaluation by two neurologists blinded to the EEG system used and quantitatively by spectral analysis of the rsEEG. The P100 visual evoked potential (VEP) and P3 event-related potential (ERP) were compared in terms of latency, amplitude and pre-stimulus noise. The majority of subjects preferred the dry electrode headset. Both neurologists reported that all rsEEG traces were comparable between the wet and dry electrode headsets. Absolute Alpha and Beta power during rest did not statistically differ between the two EEG systems (p > 0.05 in all cases). However, Theta and Delta power was slightly higher with the dry electrodes (p = 0.0004 for Theta and p < 0.0001 for Delta). For ERPs, the mean latencies and amplitudes of the P100 VEP and P3 ERP showed comparable values (p > 0.10 in all cases) with a similar spatial distribution for both wet and dry electrode systems. These results suggest that the signal quality, ease of setup and portability of the dry electrode EEG headset used in our study comply with the needs of clinical applications. The quality of scalp electroencephalogram (EEG) recordings critically depends on the connection between the amplifier input and the skin surface. Wet electrodes that rely on conductive gel to guarantee low impedance levels (<10 KOhm) remain the gold standard for clinical recordings. However, EEG recording with wet electrodes requires skin abrasion, gel application, impedance optimization and cleaning after recording, all of which are time consuming. Trained EEG technicians are therefore recommended for wet electrode EEG setup and acquisition (for instance, see 1-3). However, this presents a barrier to realising diagnostic strategies that propose replacing EEG recordings in the clinic or the doctor's office with EEG recordings in the patient's home, which saves both time and costs as well as improving the patient's health care and comfort 4,5. To achieve reliable home-based EEG recording, electrodes must be easy to apply and provide stable data quality over long recording sessions. The same standards hold for other applications, including repeated EEG

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mentioning

confidence: 99%

Comparison between a wireless dry electrode EEG system with a conventional wired wet electrode EEG system for clinical applications

Hinrichs

Scholz

Baum

et al. 2020

Sci Rep

138

101

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“…With an agar concentration of 4%, applications such as EEG experiments using dry multi-pin electrodes become feasible [24].…”

Section: Discussionmentioning

confidence: 99%

Head phantoms for bioelectromagnetic applications: a material study

Hunold

Machts

Haueisen

2020

Preprint

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Background Assessments of source reconstruction procedures in electroencephalography and computations of transcranial electrical stimulation profiles require verification and validation with the help of ground truth configurations as implemented by physical head phantoms. Phantoms provide well-defined volume conduction configurations with realistic geometries.We aim to characterize the electrical conductivity of materials for modeling head compartments to establish reproducible and stable physical head phantoms. We analyzed sodium chloride (NaCl) solution, agarose hydrogel, gypsum and reed sticks as surrogate materials for the intracranial volume, scalp, skull and anisotropic conductivity structures. We measured the impedance of all materials when immersed in NaCl solution using a four-point setup. The electrical conductivity values of each material were calculated from the temperature compensated impedances considering the sample geometries. Results We obtained conductivities of 0.332 S/m (0.17 % NaCl solution), 0.0425 S/m and 0.0017 S/m (gypsum with and without NaCl), 0.314 S/m, 0.30 S/m, 0.311 S/m (2 %, 3 %, 4 % agarose). The reed sticks were tested in longitudinal and transversal direction and showed anisotropic conductivity with a ratio of 1:2.8. Conclusion We conclude that the tested materials NaCl solution, gypsum and agarose can serve as stable representation of the three main conductivity compartments of the head, intracranial volume, skull and scalp. An anisotropic conductivity structure such as a piece of white matter can be modeled using tailored reed sticks inside a volume conductor.

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“…Adapting the agar concentration in the range from 2 % to 4 % allowed modifying its mechanical durability without changing the conductivity to an unacceptable range. With an agar concentration of 4 %, applications such as EEG experiments using dry multi-pin electrodes become feasible [24].…”

Section: Discussionmentioning

confidence: 99%

Head phantoms for bioelectromagnetic applications: a material study

Hunold

Machts

Haueisen

2020

Preprint

Self Cite

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Background: Assessments of source reconstruction procedures in electroencephalography and computations of transcranial electrical stimulation profiles require verification and validation with the help of ground truth configurations as implemented by physical head phantoms.. For these phantoms, synthetic materials are needed, which are mechanically and electrochemically stable and possess conductivity values similar to the modeled human head tissues. Typical three-compartment head models comprise a scalp layer with a conductivity range from 0.137 S/m to 2.1 S/m, a skull layer with conductivity values between 0.066 S/m and 0.00275 S/m, and an intracranial volume with an often-used average conductivity value of 0.33 S/m. To establish a realistically shaped physical head phantom with a well-defined volume conduction configuration we here characterize the electrical conductivity of synthetic materials for modeling head compartments. We analyze agarose hydrogel, gypsum, and sodium chloride (NaCl) solution as surrogate materials for scalp, skull, and intracranial volume. We measure the impedance of all materials when immersed in NaCl solution using a four-electrode setup. The measured impedance values, temperature compensated to 25°C, were used to calculate the electrical conductivity values of each material. Further, the conductivities in the longitudinal and transversal directions of reed sticks immersed in NaCl solution were measured to test their suitability for mimicking the anisotropic conductivity of white matter tracts.Results: We obtained conductivities of 0.314 S/m, 0.30 S/m, 0.311 S/m (2 %, 3 %, 4 % agarose), 0.0425 S/m and 0.0017 S/m (gypsum with and without NaCl in the compound), and 0.332 S/m (0.17 % NaCl solution). These values are within the range of the conductivity values used for EEG and TES modeling. The reed sticks showed anisotropic conductivity with a ratio of 1:2.8. Conclusion: We conclude that the tested materials agarose, gypsum, and NaCl solution can serve as stable representations of the three main conductivity compartments of the head scalp, skull, and intracranial volume. An anisotropic conductivity structure such as a fiber track in white matter can be modeled using tailored reed sticks inside a volume conductor.

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Contact Pressure and Flexibility of Multipin Dry EEG Electrodes

Cited by 68 publications

References 33 publications

Comparison between a wireless dry electrode EEG system with a conventional wired wet electrode EEG system for clinical applications

Comparison between a wireless dry electrode EEG system with a conventional wired wet electrode EEG system for clinical applications

Head phantoms for bioelectromagnetic applications: a material study

Head phantoms for bioelectromagnetic applications: a material study

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