Validation of Computational Studies for Electrical Brain Stimulation With Phantom Head Experiments

Kim, Donghyeon; Jeong, Jinmo; Jeong, Sangdo; Kim, Sohee; Jun, Sung Chan; Chung, Euiheon

doi:10.1016/j.brs.2015.06.009

Cited by 36 publications

(44 citation statements)

References 44 publications

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“…Obviously, a human head is not three-layered and perfectly spherical. A study by Kim et al (2015), however, showed that the three-layer spherical model is quite accurate in capturing the essential characteristics of the electric-stimulation-generated ohmic currents in scalp, skull and the brain. Another difference lies in the sources of activity: Contrary to the many sources in a human brain, our phantom only had one neural source.…”

Section: Discussionmentioning

confidence: 99%

Signal-space projection suppresses the tACS artifact in EEG recordings

Vosskuhl

Mutanen

Neuling

et al. 2019

Preprint

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24 25 26 2 1. Abstract 27Background: To probe the functional role of brain oscillations, transcranial alternating current 28 stimulation (tACS) has proven to be a useful neuroscientific tool. Because of the huge tACS-caused 29 artifact in electroencephalography (EEG) signals, tACS-EEG studies have been mostly limited to 30 compare brain activity between recordings before and after concurrent tACS. Critically, attempts to 31 suppress the artifact in the data cannot assure that the entire artifact is removed while brain activity 32 is preserved. The current study aims to evaluate the feasibility of specific artifact correction 33 techniques to clean tACS-contaminated EEG data. 34New Method: In the first experiment, we used a phantom head to have full control over the signal 35 to be analyzed. Driving pre-recorded human brain-oscillation signals through a dipolar current 36 source within the phantom, we simultaneously applied tACS and compared the performance of 37 different artifact-correction techniques: sine subtraction, template subtraction, and signal-space 38 projection (SSP). In the second experiment, we combined tACS and EEG on a human subject to 39 validate the best-performing data-correction approach. 40Results: The tACS artifact was highly attenuated by SSP in the phantom and the human EEG; thus, 41 we were able to recover the amplitude and phase of the oscillatory activity. In the human experiment, 42 event-related desynchronization could be restored after correcting the artifact. 43Comparison with existing methods: The best results were achieved with SSP, which outperformed 44 sine subtraction and template subtraction. 45 Conclusions: Our results demonstrate the feasibility of SSP by applying it to human tACS-EEG 46 data. 47 48 Keywords: 49 Electroencephalography, transcranial alternating current stimulation, tACS, artifact, signal space 50 projection, phantom head 51 52 3 2. Introduction 53 The goal of transcranial alternating current stimulation (tACS) is often the modulation of oscillatory 54 brain activity and the concurrent demonstration of behavioral consequences of the intervention 55 (Herrmann et al., 2013). Thus far, most studies combining tACS with electroencephalography 56 (EEG) have demonstrated effects on oscillatory brain activity only by comparing the EEG before 57 and after tACS (Zaehle et al. 2010; Vossen et al. 2015; Kasten and Herrmann 2017), because EEG 58 data recorded during stimulation is contaminated by the huge tACS-generated artifact. As a 59 workaround, behavioral effects found during application of tACS have been interpreted as a proxy 60 of changes of brain oscillations (Polanía et al. 2012; Neuling et al. 2012; Cecere et al. 2015). 61 In the case of magnetoencephalography (MEG), the correction of the tACS artifact is simpler than 62 in EEG since the MEG sensors are not connected to the tACS electrodes via the skin (Neuling et 63 al., 2015). The issue of tACS artifact correction in MEG data is discussed elsewhere (Neuling et al. 64 2015, 2017; Noury et al. ...

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Section: Discussionmentioning

confidence: 99%

Signal-space projection suppresses the tACS artifact in EEG recordings

Vosskuhl

Mutanen

Neuling

et al. 2019

Preprint

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“…Figure 2 illustrates examples of anthropomorphic physical phantoms and quality control phantoms. Currently, anthropomorphic physical phantoms have also been used for experimental studies to validate computer simulations by comparing directly both dosimetric data [35][36][37][38][39][40].…”

Section: Phantoms For Quality Control Anthropomorphic Phantoms and mentioning

confidence: 99%

Anthropomorphic Phantoms - Potential for More Studies and Training in Radiology

Ramos¹,

Thomas²,

Berdeguez³

et al. 2017

IJRRT

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Anthropomorphic phantoms are used for the assessment of image quality and to simulate a medical procedure. They can be likewise developed for training and teaching for all modalities of imaging. Phantoms built from tissue-equivalent materials provide a physical representation of the anatomy of the human body and attenuation characteristics, allowing researchers to calculate absorbed organ doses, improving treatments effectiveness and protecting healthy tissues. Nowadays, physical phantoms have been used as a comparison to computational models for validation of Monte Carlo codes, which are computational phantoms. The more complex the tissue is structured, the more difficult it gets to design the phantom. With the development of 3D printers, new phantoms can be built from medical imaging. However, current 3D printers do not use a wide variety of materials, so it is not possible yet to create phantoms for functional imaging. Studies must be performed to optimize current imaging techniques and elevate their accuracy, which would provide visual, practical, hands-on training of the medical staff, with real-world simulations, ideally patient-specific. This technological advance should be made with physical and computational phantoms in parallel since validation has a high value to the reliability of this scientific method. When it comes to radiation protection of patients and staff, new anthropomorphic phantoms could also provide data for new dosimetry and radiation protection studies, serving as a foundation for the progress of radiological safety throughout the world.

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“…Alternatively, homogeneous electrolyte concentration across compartments can be applied in combination with structural conductivity barriers provided by porous materials. This independence from electrolyte concentration gradients leads to temporal stability, especially in comparison to post-mortem skull [8,9] and agar-based phantoms [10][11][12]. However, introducing a porous material as structural conductivity barrier into a saline solution leads to infiltration of the saline solution into the porous material.…”

Section: Introductionmentioning

confidence: 99%

Head phantoms for electroencephalography and transcranial electric stimulation: a skull material study

Hunold

Strohmeier

Fiedler

et al. 2018

Biomedical Engineering / Biomedizinische Technik

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Physical head phantoms allow the assessment of source reconstruction procedures in electroencephalography and electrical stimulation profiles during transcranial electric stimulation. Volume conduction in the head is strongly influenced by the skull, which represents the main conductivity barrier. Realistic modeling of its characteristics is thus important for phantom development. In the present study, we proposed plastic clay as a material for modeling the skull in phantoms. We analyzed five clay types varying in granularity and fractions of fire clay, each with firing temperatures from 550°C to 950°C. We investigated the conductivity of standardized clay samples when immersed in a 0.9% sodium chloride solution with time-resolved four-point impedance measurements. To test the reusability of the clay model, these measurements were repeated after cleaning the samples by rinsing in deionized water for 5 h. We found time-dependent impedance changes for approximately 5 min after immersion in the solution. Thereafter, the conductivities stabilized between 0.0716 S/m and 0.0224 S/m depending on clay type and firing temperatures. The reproducibility of the measurement results proved the effectiveness of the rinsing procedure. Clay provides formability, is permeable to ions, can be adjusted in conductivity value and is thus suitable for the skull modeling in phantoms.

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Validation of Computational Studies for Electrical Brain Stimulation With Phantom Head Experiments

Cited by 36 publications

References 44 publications

Signal-space projection suppresses the tACS artifact in EEG recordings

Signal-space projection suppresses the tACS artifact in EEG recordings

Anthropomorphic Phantoms - Potential for More Studies and Training in Radiology

Head phantoms for electroencephalography and transcranial electric stimulation: a skull material study

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