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Franco-Rosado P, Callejón MA, Reina-Tosina J, Roa LM, Martin-Rodriguez JF, Mir P. Addressing the sources of inter-subject variability in E-field parameters in anodal tDCS stimulation over motor cortical network. Phys Med Biol 2024; 69:145013. [PMID: 38917834 DOI: 10.1088/1361-6560/ad5bb9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 06/25/2024] [Indexed: 06/27/2024]
Abstract
Objetive: .Although transcranial direct current stimulation constitutes a non-invasive neuromodulation technique with promising results in a great variety of applications, its clinical implementation is compromised by the high inter-subject variability reported. This study aims to analyze the inter-subject variability in electric fields (E-fields) over regions of the cortical motor network under two electrode montages: the classical C3Fp2 and an alternative P3F3, which confines more the E-field over this region.Approach.Computational models of the head of 98 healthy subjects were developed to simulate the E-field under both montages. E-field parameters such as magnitude, focality and orientation were calculated over three regions of interest (ROI): M1S1, supplementary motor area (SMA) and preSMA. The role of anatomical characteristics as a source of inter-subject variability on E-field parameters and individualized stimulation intensity were addressed using linear mixed-effect models.Main results.P3F3 showed a more confined E-field distribution over M1S1 than C3Fp2; the latter elicited higher E-fields over supplementary motor areas. Both montages showed high inter-subject variability, especially for the normal component over C3Fp2. Skin, bone and CSF ROI volumes showed a negative association with E-field magnitude irrespective of montage. Grey matter volume and montage were the main sources of variability for focality. The curvature of gyri was found to be significantly associated with the variability of normal E-fields.Significance.Computational modeling proves useful in the assessment of E-field variability. Our simulations predict significant differences in E-field magnitude and focality for C3Fp2 and P3F3. However, anatomical characteristics were also found to be significant sources of E-field variability irrespective of electrode montage. The normal E-field component better captured the individual variability and low rate of responder subjects observed in experimental studies.
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Affiliation(s)
- Pablo Franco-Rosado
- Unidad de Trastornos del Movimiento, Servicio de Neurología, Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Sevilla, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain
- Grupo de Ingeniería Biomédica, Departamento de Teoría de la Señal y Comunicaciones, Universidad de Sevilla, Sevilla, Spain
- Departamento de Psicología Experimental, Universidad de Sevilla, Sevilla, Spain
| | - M Amparo Callejón
- Grupo de Ingeniería Biomédica, Departamento de Teoría de la Señal y Comunicaciones, Universidad de Sevilla, Sevilla, Spain
- Servicio de Otorrinolaringología, Hospital Universitario Virgen Macarena, Sevilla, Spain
| | - Javier Reina-Tosina
- Grupo de Ingeniería Biomédica, Departamento de Teoría de la Señal y Comunicaciones, Universidad de Sevilla, Sevilla, Spain
| | - Laura M Roa
- Grupo de Ingeniería Biomédica, Departamento de Teoría de la Señal y Comunicaciones, Universidad de Sevilla, Sevilla, Spain
| | - Juan F Martin-Rodriguez
- Unidad de Trastornos del Movimiento, Servicio de Neurología, Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Sevilla, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain
- Departamento de Psicología Experimental, Universidad de Sevilla, Sevilla, Spain
| | - Pablo Mir
- Unidad de Trastornos del Movimiento, Servicio de Neurología, Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Sevilla, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain
- Departamento de Medicina, Facultad de Medicina, Universidad de Sevilla, Sevilla, Spain
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Zhang S, Qin Y, Wang J, Yu Y, Wu L, Zhang T. Noninvasive Electrical Stimulation Neuromodulation and Digital Brain Technology: A Review. Biomedicines 2023; 11:1513. [PMID: 37371609 DOI: 10.3390/biomedicines11061513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 05/17/2023] [Accepted: 05/22/2023] [Indexed: 06/29/2023] Open
Abstract
We review the research progress on noninvasive neural regulatory systems through system design and theoretical guidance. We provide an overview of the development history of noninvasive neuromodulation technology, focusing on system design. We also discuss typical cases of neuromodulation that use modern noninvasive electrical stimulation and the main limitations associated with this technology. In addition, we propose a closed-loop system design solution of the "time domain", "space domain", and "multi-electrode combination". For theoretical guidance, this paper provides an overview of the "digital brain" development process used for noninvasive electrical-stimulation-targeted modeling and the development of "digital human" programs in various countries. We also summarize the core problems of the existing "digital brain" used for noninvasive electrical-stimulation-targeted modeling according to the existing achievements and propose segmenting the tissue. For this, the tissue parameters of a multimodal image obtained from a fresh cadaver were considered as an index. The digital projection of the multimodal image of the brain of a living individual was implemented, following which the segmented tissues could be reconstructed to obtain a "digital twin brain" model with personalized tissue structure differences. The "closed-loop system" and "personalized digital twin brain" not only enable the noninvasive electrical stimulation of neuromodulation to achieve the visualization of the results and adaptive regulation of the stimulation parameters but also enable the system to have individual differences and more accurate stimulation.
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Affiliation(s)
- Shuang Zhang
- The School of Artificial Intelligence, Neijiang Normal University, Neijiang 641000, China
- The School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu 610056, China
- The NJNU-OMNISKY Smart Medical Engineering Applications Joint Laboratory, Neijiang Normal University, Neijiang 641004, China
- The High Field Magnetic Resonance Brain Imaging Laboratory of Sichuan, Chengdu 610056, China
| | - Yuping Qin
- The School of Artificial Intelligence, Neijiang Normal University, Neijiang 641000, China
- The NJNU-OMNISKY Smart Medical Engineering Applications Joint Laboratory, Neijiang Normal University, Neijiang 641004, China
| | - Jiujiang Wang
- The School of Artificial Intelligence, Neijiang Normal University, Neijiang 641000, China
- The NJNU-OMNISKY Smart Medical Engineering Applications Joint Laboratory, Neijiang Normal University, Neijiang 641004, China
| | - Yuanyu Yu
- The School of Artificial Intelligence, Neijiang Normal University, Neijiang 641000, China
- The NJNU-OMNISKY Smart Medical Engineering Applications Joint Laboratory, Neijiang Normal University, Neijiang 641004, China
| | - Lin Wu
- The School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu 610056, China
- The High Field Magnetic Resonance Brain Imaging Laboratory of Sichuan, Chengdu 610056, China
| | - Tao Zhang
- The School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu 610056, China
- The High Field Magnetic Resonance Brain Imaging Laboratory of Sichuan, Chengdu 610056, China
- The Sichuan Institute for Brain Science and Brain-Inspired Intelligence, Chengdu 610056, China
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Inter-Individual Variability in tDCS Effects: A Narrative Review on the Contribution of Stable, Variable, and Contextual Factors. Brain Sci 2022; 12:brainsci12050522. [PMID: 35624908 PMCID: PMC9139102 DOI: 10.3390/brainsci12050522] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 04/08/2022] [Accepted: 04/14/2022] [Indexed: 01/27/2023] Open
Abstract
Due to its safety, portability, and cheapness, transcranial direct current stimulation (tDCS) use largely increased in research and clinical settings. Despite tDCS’s wide application, previous works pointed out inconsistent and low replicable results, sometimes leading to extreme conclusions about tDCS’s ineffectiveness in modulating behavioral performance across cognitive domains. Traditionally, this variability has been linked to significant differences in the stimulation protocols across studies, including stimulation parameters, target regions, and electrodes montage. Here, we reviewed and discussed evidence of heterogeneity emerging at the intra-study level, namely inter-individual differences that may influence the response to tDCS within each study. This source of variability has been largely neglected by literature, being results mainly analyzed at the group level. Previous research, however, highlighted that only a half—or less—of studies’ participants could be classified as responders, being affected by tDCS in the expected direction. Stable and variable inter-individual differences, such as morphological and genetic features vs. hormonal/exogenous substance consumption, partially account for this heterogeneity. Moreover, variability comes from experiments’ contextual elements, such as participants’ engagement/baseline capacity and individual task difficulty. We concluded that increasing knowledge on inter-dividual differences rather than undermining tDCS effectiveness could enhance protocols’ efficiency and reproducibility.
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da Silva Machado CB, da Silva LM, Gonçalves AF, Andrade PRD, Mendes CKTT, de Assis TJCF, Godeiro Júnior CDO, Andrade SM. Multisite non-invasive brain stimulation in Parkinson's disease: A scoping review. NeuroRehabilitation 2021; 49:515-531. [PMID: 34776426 PMCID: PMC8764602 DOI: 10.3233/nre-210190] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
BACKGROUND: Parkinson’s disease (PD) is a progressive neurodegenerative disorder, characterized by cardinal motor symptoms in addition to cognitive impairment. New insights concerning multisite non-invasive brain stimulation effects have been gained, which can now be used to develop innovative treatment approaches. OBJECTIVE: Map the researchs involving multisite non-invasive brain stimulation in PD, synthesize the available evidence and discuss future directions. METHODS: The databases PubMed, PsycINFO, CINAHL, LILACS and The Cochrane Library were searched from inception until April 2020, without restrictions on the date of publication or the language in which it was published. The reviewers worked in pairs and sequentially evaluated the titles, abstracts and then the full text of all publications identified as potentially relevant. RESULTS: Twelve articles met the inclusion criteria. The target brain regions included mainly the combination of a motor and a frontal area, such as stimulation of the primary motor córtex associated with the dorsolateral prefrontal cortex. Most of the trials showed that this modality was only more effective for the motor component, or for the cognitive and/or non-motor, separately. CONCLUSIONS: Despite the results being encouraging for the use of the multisite aproach, the indication for PD management should be carried out with caution and deserves scientific deepening.
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Affiliation(s)
| | | | | | | | | | | | - Clécio de Oliveira Godeiro Júnior
- Division of Neurology, CHU of Grenoble, Grenoble Alpes University, La Tronche, Grenoble, France.,Division of Neurology, Hospital Universitario Onofre Lopes, Federal University of Rio Grande do Norte, Natal, Brazil
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Seo H, Jun SC. Computational exploration of epidural cortical stimulation using a realistic head model. Comput Biol Med 2021; 135:104290. [PMID: 33775416 DOI: 10.1016/j.compbiomed.2021.104290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 02/15/2021] [Indexed: 10/21/2022]
Abstract
Motor cortex stimulation, either non-invasively or with implanted electrodes, has been applied worldwide as a treatment for intractable neuropathic pain syndromes. Although computer simulations of non-invasive brain stimulation have been investigated largely to optimize protocols and improve our understanding of underlying mechanisms using a realistic head model, computational studies of invasive cortical stimulation are rare and limited to very simplified cortical models. In this paper, we present an anatomically realistic head model for epidural cortical stimulation that includes the most sophisticated epidural electrodes with an insulating paddle. The head model predicted the stimulus-induced field strengths according to two different stimulation techniques, bipolar and monopolar stimulations. We found that the stimulus-induced field focused on the precentral and postcentral gyri because of the epidural lead's invasiveness. Different stimulation configurations influenced the shape of the field markedly, and complex patterns of inward and outward directions of the radial field were observed in bipolar stimulation compared to those in monopolar stimulation. The spatial distributions of field strength showed that the optimal stimulation varied according to the target areas. In conclusion, we proposed an anatomically realistic head model and a sophisticated epidural lead to simulate epidural cortical stimulation-induced field strengths and identified the importance of such detailed modeling for epidural cortical stimulation because of the current's shunting through the cerebrospinal fluid.
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Affiliation(s)
- Hyeon Seo
- School of Electrical Engineering and Computer Science, Gwangju Institute of Science & Technology, South Korea; Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, South Korea
| | - Sung Chan Jun
- School of Electrical Engineering and Computer Science, Gwangju Institute of Science & Technology, South Korea.
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Lefebvre S, Jann K, Schmiesing A, Ito K, Jog M, Schweighofer N, Wang DJJ, Liew SL. Differences in high-definition transcranial direct current stimulation over the motor hotspot versus the premotor cortex on motor network excitability. Sci Rep 2019; 9:17605. [PMID: 31772347 PMCID: PMC6879500 DOI: 10.1038/s41598-019-53985-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 11/06/2019] [Indexed: 01/07/2023] Open
Abstract
The effectiveness of transcranial direct current stimulation (tDCS) placed over the motor hotspot (thought to represent the primary motor cortex (M1)) to modulate motor network excitability is highly variable. The premotor cortex-particularly the dorsal premotor cortex (PMd)-may be a promising alternative target to reliably modulate motor excitability, as it influences motor control across multiple pathways, one independent of M1 and one with direct connections to M1. This double-blind, placebo-controlled preliminary study aimed to differentially excite motor and premotor regions using high-definition tDCS (HD-tDCS) with concurrent functional magnetic resonance imaging (fMRI). HD-tDCS applied over either the motor hotspot or the premotor cortex demonstrated high inter-individual variability in changes on cortical motor excitability. However, HD-tDCS over the premotor cortex led to a higher number of responders and greater changes in local fMRI-based complexity than HD-tDCS over the motor hotspot. Furthermore, an analysis of individual motor hotspot anatomical locations revealed that, in more than half of the participants, the motor hotspot is not located over anatomical M1 boundaries, despite using a canonical definition of the motor hotspot. This heterogeneity in stimulation site may contribute to the variability of tDCS results. Altogether, these preliminary findings provide new considerations to enhance tDCS reliability.
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Affiliation(s)
- Stephanie Lefebvre
- Neural Plasticity and Neurorehabilitation Laboratory, Chan Division of Occupational Science and Occupational Therapy, University of Southern California, Los Angeles, CA, United States
| | - Kay Jann
- Laboratory of FMRI Technology (LOFT), USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA
- Laboratory of Neuro Imaging (LONI), USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA
| | - Allie Schmiesing
- Neural Plasticity and Neurorehabilitation Laboratory, Chan Division of Occupational Science and Occupational Therapy, University of Southern California, Los Angeles, CA, United States
| | - Kaori Ito
- Neural Plasticity and Neurorehabilitation Laboratory, Chan Division of Occupational Science and Occupational Therapy, University of Southern California, Los Angeles, CA, United States
| | - Mayank Jog
- Laboratory of FMRI Technology (LOFT), USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA
- Laboratory of Neuro Imaging (LONI), USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA
| | - Nicolas Schweighofer
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, USA
| | - Danny J J Wang
- Laboratory of FMRI Technology (LOFT), USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA
- Laboratory of Neuro Imaging (LONI), USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA
| | - Sook-Lei Liew
- Neural Plasticity and Neurorehabilitation Laboratory, Chan Division of Occupational Science and Occupational Therapy, University of Southern California, Los Angeles, CA, United States.
- Laboratory of Neuro Imaging (LONI), USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA.
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Im C, Seo H, Jun SC. Stimulation Effect of Inter-subject Variability in tDCS-Multi-scale Modeling Study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2019; 2018:3092-3095. [PMID: 30441048 DOI: 10.1109/embc.2018.8513056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Transcranial direct current stimulation (tDCS) is an emerging non-invasive neuromodulation method that is convenient and popular in clinical use. However, there is a practical issue in applying tDCS; it is difficult to optimize the montage for each individual because of inherent inter-subject variability. Thus, the stimulation effect of such individual anatomical head variation has been investigated using anatomically realistic models. In this work, we developed a multi-scale computational model, which combined head models based on magnetic resonance imaging (MRI) and multi-compartmental neuronal models of pyramidal neurons (PNs), to investigate both the macroscopic and microscopic effects oftDCS. We constructed three different head models and compared the stimulation effects of tDCS in the primary cortex area (Brodmann area 4) with respect to the electric fields induced and steady-state membrane polarizations. We observed that the electric field behavior and induced somatic polarizations varied across subjects in accordance with the thicknesses of cerebrospinal fluid (CSF) and skull measured in each model. Thus, we concluded that variations in the CSF and skull might be correlated with the effects of tDCS.
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Evaluation of acute anodal direct current stimulation-induced effects on somatosensory-evoked responses in the rat. Brain Res 2019; 1720:146318. [DOI: 10.1016/j.brainres.2019.146318] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Revised: 06/29/2019] [Accepted: 07/01/2019] [Indexed: 01/02/2023]
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Seo H, Jun SC. Relation between the electric field and activation of cortical neurons in transcranial electrical stimulation. Brain Stimul 2019; 12:275-289. [DOI: 10.1016/j.brs.2018.11.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 10/03/2018] [Accepted: 11/06/2018] [Indexed: 12/12/2022] Open
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Seo H, Jun SC. Multi-Scale Computational Models for Electrical Brain Stimulation. Front Hum Neurosci 2017; 11:515. [PMID: 29123476 PMCID: PMC5662877 DOI: 10.3389/fnhum.2017.00515] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 10/11/2017] [Indexed: 12/11/2022] Open
Abstract
Electrical brain stimulation (EBS) is an appealing method to treat neurological disorders. To achieve optimal stimulation effects and a better understanding of the underlying brain mechanisms, neuroscientists have proposed computational modeling studies for a decade. Recently, multi-scale models that combine a volume conductor head model and multi-compartmental models of cortical neurons have been developed to predict stimulation effects on the macroscopic and microscopic levels more precisely. As the need for better computational models continues to increase, we overview here recent multi-scale modeling studies; we focused on approaches that coupled a simplified or high-resolution volume conductor head model and multi-compartmental models of cortical neurons, and constructed realistic fiber models using diffusion tensor imaging (DTI). Further implications for achieving better precision in estimating cellular responses are discussed.
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Affiliation(s)
- Hyeon Seo
- School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, Gwangju, South Korea
| | - Sung C. Jun
- School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, Gwangju, South Korea
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A novel 3D-printed head phantom with anatomically realistic geometry and continuously varying skull resistivity distribution for electrical impedance tomography. Sci Rep 2017; 7:4608. [PMID: 28676697 PMCID: PMC5496891 DOI: 10.1038/s41598-017-05006-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 05/23/2017] [Indexed: 11/15/2022] Open
Abstract
Phantom experiments are an important step for testing during the development of new hardware or imaging algorithms for head electrical impedance tomography (EIT) studies. However, due to the sophisticated anatomical geometry and complex resistivity distribution of the human head, constructing an accurate phantom for EIT research remains challenging, especially for skull modelling. In this paper, we designed and fabricated a novel head phantom with anatomically realistic geometry and continuously varying skull resistivity distribution based on 3D printing techniques. The skull model was constructed by simultaneously printing the distinct layers inside the skull with resistivity-controllable printing materials. The entire phantom was composed of saline skin, a 3D-printed skull, saline cerebrospinal fluid (CSF) and 3D-printed brain parenchyma. The validation results demonstrated that the resistivity of the phantom was in good agreement with that of human tissue and was stable over time, and the new phantom performed well in EIT imaging. This paper provides a standardized, efficient and reproducible method for the construction of a head phantom for EIT that could be easily adapted to other conditions for manufacturing head phantoms for brain function research, such as transcranial direct current stimulation (TDCS) and electroencephalography (EEG).
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Seo H, Kim HI, Jun SC. A computational study on effect of a transcranial channel as a skull/brain interface in the conventional rectangular patch-type transcranial direct current stimulation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2017:1946-1949. [PMID: 29060274 DOI: 10.1109/embc.2017.8037230] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A conceptual model of a transcranial channel was recently proposed for conveying external currents of the skull to the brain; the effects of the transcranial channel combined with high-definition transcranial direct current stimulation (HD-tDCS) was investigated, resulting in discovery of increased stimulus intensity and focality. In this work, rather than HD-tDCS using smaller disc-type electrodes, we proposed the use of the transcranial channel with conventional tDCS using larger patch electrodes. We used multi-scale computational models that couple an anatomically realistic head model with multi-compartmental models of cortical neurons. We then predicted the excitability in the hand knob (target area) based on stimulus-induced electric fields and steady-state membrane polarizations. Conventional tDCS without the transcranial channel resulted in diffuse distributions of electric fields that covered the frontal cortex, while the spatial focality and intensity of the excitability increased significantly at the target area in the presence of the transcranial channel. Thus, it is expected that conventional tDCS with the transcranial channel allows a better targeting neuromodulation with higher intensity and may be promising for applying prolonged and stabilized tDCS.
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