scholarly journals Personalization of Multi-electrode Setups in tCS/tES: Methods and Advantages

2020 ◽  
pp. 119-135
Author(s):  
R. Salvador ◽  
M. C. Biagi ◽  
O. Puonti ◽  
M. Splittgerber ◽  
V. Moliadze ◽  
...  
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Cortical Excitability ◽  
Field Amplitude ◽  
Head Model ◽  
Mri Segmentation ◽  
Field Distributions ◽  
Multichannel Systems ◽  
Precise Tool ◽  
Anatomical Parameters

AbstractTranscranial current stimulation (tCS or tES) protocols yield results that are highly variable across individuals. Part of this variability results from differences in the electric field (E-field) induced in subjects’ brains during stimulation. The E-field determines how neurons respond to stimulation, and it can be used as a proxy for predicting the concurrent effects of stimulation, like changes in cortical excitability, and, ultimately, its plastic effects. While the use of multichannel systems with small electrodes has provided a more precise tool for delivering tCS, individually variable anatomical parameters like the shape and thickness of tissues affect the E-field distribution for a specific electrode montage. Therefore, using the same montage parameters across subjects does not lead to the homogeneity of E-field amplitude over the desired targets. Here we describe a pipeline that leverages individualized head models combined with montage optimization algorithms to reduce the variability of the E-field distributions over subjects in tCS. We will describe the different steps of the pipeline – namely, MRI segmentation and head model creation, target specification, and montage optimization – and discuss their main advantages and limitations.

Potential and Electric Field Distribution of 220kV Insulator String with a Faulty Insulator under Windage Yaw Condition

2014 ◽  
Vol 521 ◽  
pp. 317-320
Author(s):  
Hui Hui Li ◽  
Zheng Zheng ◽  
Hong Bo Chen ◽  
Huan Bai ◽  
Hua Zhao Zhang ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Field Strength ◽  
Electric Field ◽  
Field Distribution ◽  
Electric Field Distribution ◽  
Field Distributions ◽  
Space Potential ◽  
Suspension Insulator ◽  
Variation Characteristics

Faulty insulators could appear in the HV transmission line insulator string under the comprehensive effect of electrical, mechanical and environmental factors and they can be detected according to the space potential and electric field distribution variation characteristics around the insulator string. Finite Element Method (FEM) was used to study the potential and electric field distributions of a 220kV suspension insulator string contained a zero-value insulator in windage condition, comparing with a fine insulator string. The results show that the variation of the space potential and electric field distributions of insulator string is the same as that under no windage condition. The curve of synthetic electric field along the central axis around the good insulator string is U-shape. The 10th and 11th insulators from the high-voltage end are the sensitive insulators where the distortion ratio of synthetic field strength is higher than 3%, when a faulty insulator is in the string. This result can provide preferences for the online detection of faulty insulators.

scholarly journals Calculation of electromagnetic field from mobile phone induced in the pituitary gland of children head model

2017 ◽  
Vol 74 (9) ◽  
pp. 854-861 ◽  
Author(s):  
Vladimir Stankovic ◽  
Dejan Jovanovic ◽  
Dejan Krstic ◽  
Vera Markovic ◽  
Momir Dunjic
Keyword(s):  
Electromagnetic Field ◽  
Electric Field ◽  
Pituitary Gland ◽  
Mobile Phone ◽  
Penetration Depth ◽  
Field Distribution ◽  
Mobile Communications ◽  
Electric Field Distribution ◽  
Head Model ◽  
Exposure Limits

Background/Aim. A mobile phone is a source of electromagnetic radiation located close to the head and consequently its intense use may cause harmful effects particularly in younger population. The aim of this study was to investigate the influence of electromagnetic field of the mobile phone on the pituitary gland of the child. Methods. In order to obtain the more accurate results for this research 3D realistic model of child's head whose size corresponds to an average child (7 years old) was created. Electric field distribution in child head model and values of Specific Absorption Rate (SAR) at the region of pituitary gland were determined. This study was performed for the frequencies of 900 MHz, 1800 MHz, and 2100 MHz, as the most commonly used in mobile communications. The special attention was dedicated to the values of the electric field and the values of the SAR in the pituitary gland. For all frequencies over 10 g and 1 g of tissue average SAR was calculated. The electric field distribution and values of average SAR for 10 g and 1 g trough the model of child's head were obtained by the using numerical calculation based on the Finite Integration Technique (FIT). Results. The largest value of electric field in the region of the pituitary gland was at the frequency of 900 MHz, as a consequence of the highest penetration depth. Lower values of the electric field in the region of the pituitary gland were at frequencies of 1,800 MHz and 2,100 MHz. The SAR in the pituitary gland decreased as the frequency increased as a direct consequence of lower penetration depth. Conclusion. The electric field strength from a mobile phone is higher than the value specified by standards for the maximum allowable exposure limits. The high values of the electric field are not only in the vicinity of a mobile phone but also in tissues and organs of the human head. Particular attention should be paid to the exposure of children to radiation of mobile phones. Smaller dimensions of children?s head and smaller thickness of tissues and organs have as a consequence greater penetration of electromagnetic waves.

scholarly journals Individual head models for estimating the TMS-induced electric field in rat brain

2019 ◽  
Author(s):  
Lari M. Koponen ◽  
Matti Stenroos ◽  
Jaakko O. Nieminen ◽  
Kimmo Jokivarsi ◽  
Olli Gröhn ◽  
...  
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Magnetic Stimulation ◽  
Cortical Activation ◽  
Head Model ◽  
Spherically Symmetric ◽  
Simple Method ◽  
X Ray ◽  
Conductivity Profile ◽  
The Brain

AbstractIn transcranial magnetic stimulation (TMS), the initial cortical activation due to stimulation is determined by the state of the brain and the magnitude, waveform, and direction of the induced electric field (E-field) in the cortex. The E-field distribution depends on the conductivity geometry of the head. The effects of deviations from a spherically symmetric conductivity profile have been studied in detail in humans. In small mammals, such as rats, these effects are more pronounced due to their smaller and less spherical heads. In this study, we describe a simple method for building individual realistically shaped head models for rats from high-resolution X-ray tomography images. We computed the TMS-induced E-field with the boundary element method and assessed the effect of head-model simplifications on the estimated E-field. The deviations from spherical symmetry have large, non-trivial effects on the E-field distribution: in some cases, even the direction of the E-field in the cortex cannot be reliably predicted by the coil orientation unless these deviations are properly considered.

scholarly journals Transmission Analysis in Human Body Communication for Head-Mounted Wearable Devices

Electronics ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1213
Author(s):  
Dairoku Muramatsu ◽  
Ken Sasaki
Keyword(s):  
Electric Field ◽  
Human Body ◽  
Hearing Aids ◽  
Wearable Devices ◽  
Transmission Mechanism ◽  
Signal Frequency ◽  
Head Model ◽  
Transmission Characteristics ◽  
Field Distributions ◽  
Human Body Communication

As society ages, wireless body area networks (WBANs) are expected to increasingly improve the quality of life of the elderly and disabled. One promising WBAN technology is human body communication (HBC), which utilizes part of the human body as a transmission medium. Communication between head-mounted wearable devices, such as hearing aids, is a potential HBC application. To clarify the HBC transmission mechanism between head-mounted wearable devices, this study analyzes the input impedance characteristics of the transceiver electrodes, transmission characteristics, and electric field distributions around and through a detailed head model. The investigation was performed via an electromagnetic field simulation. The signal frequency had less effect on the transmission characteristics and electric field distributions at 10, 20, and 30 MHz. However, the transmission mechanism between the head-mounted wearable devices was influenced by the number of electrodes in the transceiver. Moreover, the transmission characteristics between two-electrode transceivers were improved by impedance matching. Finally, the availability of the proposed system was evaluated from power consumption and human safety perspectives.

scholarly journals Individual head models for estimating the TMS-induced electric field in rat brain

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Lari M. Koponen ◽  
Matti Stenroos ◽  
Jaakko O. Nieminen ◽  
Kimmo Jokivarsi ◽  
Olli Gröhn ◽  
...  
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Neck Region ◽  
Cortical Activation ◽  
Head Model ◽  
Simple Method ◽  
X Ray ◽  
Conductivity Profile ◽  
Spherical Head ◽  
The Brain

Abstract In transcranial magnetic stimulation (TMS), the initial cortical activation due to stimulation is determined by the state of the brain and the magnitude, waveform, and direction of the induced electric field (E-field) in the cortex. The E-field distribution depends on the conductivity geometry of the head. The effects of deviations from a spherically symmetric conductivity profile have been studied in detail in humans. In small mammals, such as rats, these effects are more pronounced due to their less spherical head, proportionally much thicker neck region, and overall much smaller size compared to the TMS coils. In this study, we describe a simple method for building individual realistically shaped head models for rats from high-resolution X-ray tomography images. We computed the TMS-induced E-field with the boundary element method and assessed the effect of head-model simplifications on the estimated E-field. The deviations from spherical symmetry have large, non-trivial effects on the E-field distribution: for some coil orientations, the strongest stimulation is in the brainstem even when the coil is over the motor cortex. With modelling prior to an experiment, such problematic coil orientations can be avoided for more accurate targeting.

Several case studies on electric field distributions for two human bodies inside the car at 3.5 GHz–5G frequency band

2021 ◽  
pp. 1-15
Author(s):  
Hilmi Akdoğan ◽  
Vasil Tabatadze ◽  
Kamil Karaçuha ◽  
Ercan Yaldiz
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Frequency Band ◽  
Electromagnetic Waves ◽  
Electric Field Distribution ◽  
Surface Element ◽  
Field Distributions ◽  
Communication Frequency ◽  
Lossy Dielectrics ◽  
First Time

The study investigates basically, the electric field distribution in a semi-closed region. Specifically, the present work focuses on the electromagnetic wave diffraction at 3.5 GHz in the vicinity of a car where two humans are located inside. The car is modeled as the perfect electric conducting object whereas the human bodies are assumed to be homogeneous lossy dielectrics. To obtain field distributions for different sceneries, the Method of Auxiliary Sources (MAS) is employed. To achieve this goal, the auxiliary sources due to each obstacle are distributed over the corresponding surface element. In the present study, two main different scenarios are considered. One or two cellphones as the source of electromagnetic waves are considered. These cellphones are operating at the proposed 5G frequency band in the European Zone. In this frequency range, the resonances are observed at 3.5 GHz which is in the range of a planned 5G communication frequency band. The present study aims to obtain quantitative and qualitative results for a better understanding of 5G healthy issues. Therefore, as a frontier study, the specific absorption rate (SAR) values are examined for the first time to answer some important questions related to 5G. For such a scenario, MAS is a very efficient, fast, and trustworthy approach to obtain field distribution at semi-closed regions.

scholarly journals A computational pipeline to determine lobular electric field distribution during cerebellar transcranial direct current stimulation

2019 ◽  
Author(s):  
Zeynab Rezaee ◽  
Anirban Dutta
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Field Distribution ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Electric Field Distribution ◽  
Head Model ◽  
Computational Pipeline ◽  
Model Interaction ◽  
Subject Specific

AbstractObjectiveCerebellar transcranial direct current stimulation (ctDCS) is challenging due to the complexity of the cerebellar structure. Therefore, our objective is to develop a freely available computational pipeline to perform cerebellar atlas-based electric field analysis using magnetic resonance imaging (MRI) guided subject-specific head modeling.MethodsWe present a freely available computational pipeline to determine subject-specific lobular electric field distribution during ctDCS. The computational pipeline can isolate subject-specific cerebellar lobules based on a spatially unbiased atlas (SUIT) for the cerebellum, and then calculates the lobular electric field distribution during ctDCS. The computational pipeline was tested in a case study using a subject-specific head model as well as using a Colin 27 Average Brain. The 5cmx5cm anode was placed 3 cm lateral to inion, and the same sized cathode was placed on the contralateral supraorbital area (called Manto montage) and buccinators muscle (called Celnik montage). A 4×1 HD-ctDCS electrode montage was also implemented for a comparison using analysis of variance (ANOVA).ResultsEta-squared effect size after three-way ANOVA for electric field strength was 0.05 for lobule, 0.00 for montage, 0.04 for head model, 0.01 for lobule*montage interaction, 0.01 for lobule* head model interaction, and 0.00 for montage*head model interaction in case of Enorm. Here, the electric field strength of both the Celnik and the Manto montages affected the lobules Crus II, VIIb, VIII, IX of the targeted cerebellar hemispheres while Manto montage had more bilateral effect. The HD-ctDCS montage primarily affected the lobules Crus I, Crus II, VIIb of the targeted cerebellar hemisphere. Our freely available computational modeling approach to analyze subject-specific lobular electric field distribution during ctDCS provided an insight into healthy human anodal ctDCS results

Modelling of the electric field distribution in the brain during tDCS

2016 ◽  
Vol 31 (5) ◽  
Author(s):  
Alexander V. Ashikhmin ◽  
Rubin R. Aliev
Keyword(s):  
Spatial Distribution ◽  
Electric Field ◽  
Field Distribution ◽  
Direct Current ◽  
Electric Field Distribution ◽  
Human Head ◽  
Head Model ◽  
Electrode Size ◽  
Common Electrode ◽  
The Brain

AbstractWe simulated the electric current distribution in the brain during transcranial direct current stimulation (tDCS) using an anatomically accurate human head model. We estimated an effect of common electrode montages on spatial distribution of the electric field during tDCS procedure and analyzed a sensitivity of the technique to variations of electrode size and orientation. We concluded that the used electrode montages are stable with respect to minor changes in electrode size and position, while an assumption of homogeneity and isotropy of the head model results in crucial changes of the electric field distribution. We determined the electrode montages suited to deliver strong effect on hippocampus and cerebellum.

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