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Abstract
Measurement of phase angle using bioimpedance analysis (BIA) has become popular as an index of so-called "cellular health". What precisely is meant by this term is not always clear but strong relationships have been found between cellular water status (the relative amounts of extra- and intracellular water), cell membrane integrity and cellular mass. Much of the current research is empirical observation and frequently pays little regard to the underlying biophysical models that underpin the BIA technique or attempts to provide mechanistic explanations for the observations. This brief review seeks to provide a basic understanding of the electrical models frequently used to describe the passive electrical properties of tissues with particular focus on phase angle. In addition, it draws attention to some practical concerns in the measurement of phase angle and notes the additional understanding that can be gained when phase angle are obtained with bioimpedance spectroscopy (BIS) rather than single frequency BIA (SFBIA) along with the potential for simulation modelling.
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Affiliation(s)
- Leigh C Ward
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, 4072, Australia.
| | - Steven Brantlov
- Department of Procurement and Clinical Engineering, Central Denmark Region, Aarhus, Denmark
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Buswinka CJ, Colesa DJ, Swiderski DL, Raphael Y, Pfingst BE. Components of impedance in a cochlear implant animal model with TGFβ1-accelerated fibrosis. Hear Res 2022; 426:108638. [PMID: 36368194 PMCID: PMC10794021 DOI: 10.1016/j.heares.2022.108638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 09/21/2022] [Accepted: 10/18/2022] [Indexed: 11/04/2022]
Abstract
Outcomes of cochlear implantation are likely influenced by the biological state of the cochlea. Fibrosis is a pathological change frequently seen in implanted ears. The goal of this work was to investigate the relationship between fibrosis and impedance. To that end, we employed an animal model of extensive fibrosis and tested whether aspects of impedance differed from controls. Specifically, an adenovirus with a TGF-β1 gene insert (Ad.TGF-β1) was injected into guinea pig scala tympani to elicit rapid onset fibrosis and investigate the relation between fibrosis and impedance. We found a significant correlation between treatment and rate of impedance increase. A physical circuit model of impedance was used to separate the effect of fibrosis from other confounding factors. Supported by preliminary, yet nonconclusive, electron microscopy data, this modeling suggested that deposits on the electrode surface are an important contributor to impedance change over time.
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Affiliation(s)
- Christopher J Buswinka
- Eaton-Peabody Laboratories, Mass Eye and Ear Hospital and Harvard Medical School, Boston MA 02114.
| | - Deborah J Colesa
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Donald L Swiderski
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Bryan E Pfingst
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, Ann Arbor, MI, 48109, USA
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Rutkove SB, Le M, Ruehr SA, Nagy JA, Semple C, Sanchez B. Design and pilot testing of a 26-gauge impedance-electromyography needle in wild-type and ALS mice. Muscle Nerve 2022; 65:702-708. [PMID: 35383969 DOI: 10.1002/mus.27551] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 02/21/2022] [Accepted: 02/25/2022] [Indexed: 11/08/2022]
Abstract
INTRODUCTION/AIMS Needle impedance-electromyography (iEMG) is a diagnostic modality currently under development that combines intramuscular electrical impedance with concentric electromyography (EMG) in a single needle. We designed, manufactured, and tested a prototype iEMG needle in a cohort of wild-type (WT) and SOD1G93A amyotrophic lateral sclerosis (ALS) mice to assess its ability to record impedance and EMG data. METHODS A new six-electrode, 26-gauge, iEMG needle was designed, manufactured and tested. Quantitative impedance and qualitative "gestalt" EMG were performed sequentially on bilateral quadriceps of 16-wk-old SOD1G93A ALS (N = 6) and WT (N = 6) mice by connecting the needle first to an impedance analyzer (with the animal at rest) and then to a standard EMG system (with the animal fully under anesthesia to measure spontaneous activity and briefly during awakening to measure voluntary activity). The needle remained in the muscle throughout the measurement period. RESULTS EMG data were qualitatively similar to that observed with a commercially available concentric EMG needle; fibrillation potentials were observed in 84% of the ALS mice and none of the WT mice; motor unit potentials were also readily identified. Impedance data revealed significant differences in resistance, reactance, and phase values between the two groups, with ALS animals having reduced reactance and resistance values. DISCUSSION This work demonstrates the feasibility of a single iEMG needle conforming to standard dimensions of size and function. Further progress of iEMG technology for enhanced neuromuscular diagnosis and quantification of disease status is currently in development.
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Affiliation(s)
- Seward B Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Mai Le
- Haystack Diagnostics, Inc, Lowell, Massachusetts, USA
| | | | - Janice A Nagy
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Carson Semple
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Benjamin Sanchez
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah, USA
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Molecular Dynamics Investigation of Spreading Performance of Physiological Saline on Surface. MATERIALS 2022; 15:ma15113925. [PMID: 35683220 PMCID: PMC9182452 DOI: 10.3390/ma15113925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 05/22/2022] [Accepted: 05/25/2022] [Indexed: 12/04/2022]
Abstract
Physiological saline is an indispensable element for maintaining the functions of life. The spreading performance of physiological saline droplets on the surface of graphene under different NaCl concentrations and electric field intensities was studied in the present work. The results show that the increase in NaCl concentration reduces the displacement vector value of molecules in droplets. In addition, NaCl is easy to aggregate on the surface of graphene. The increase in NaCl concentration makes it more difficult for droplets to penetrate the surface of graphene, and the penetration angle of droplets increases with the rise in NaCl concentration. With the increase in electric field intensity, the wetting effect of droplets is more obvious. The greater the electric field intensity is, the smaller the penetration angle is, which is mainly due to the polarity of water molecules. This study has reference significance for the study of body fluid volatilization on the human surface.
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Kwon H, Park HC, Barrera AC, Rutkove SB, Sanchez B. On the measurement of skeletal muscle anisotropic permittivity property with a single cross-shaped needle insertion. Sci Rep 2022; 12:8494. [PMID: 35589764 PMCID: PMC9120124 DOI: 10.1038/s41598-022-12289-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 05/09/2022] [Indexed: 11/10/2022] Open
Abstract
Application of minimally invasive methods to enable the measurement of tissue permittivity in the neuromuscular clinic remain elusive. This paper provides a theoretical and modeling study on the measurement of the permittivity of two-dimensional anisotropic tissues such as skeletal muscle with a multi-electrode cross-shaped needle. For this, we design a novel cross-shaped needle with multiple-electrodes and analyse apparent impedance corresponding to the measured impedance. In addition, we propose three methods of estimate anisotropic muscle permittivity. Compared to existing electrical impedance-based needle methods that we have developed, the new needle design and numerical methods associated enable estimating in vivo muscle permittivity values with only a single needle insertion. Being able to measure muscle permittivity directly with a single needle insertion could open up an entirely new area of research with direct clinical application, including using these values to assist in neuromuscular diagnosis and to assess subtle effects of therapeutic intervention on muscle health.
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Affiliation(s)
- Hyeuknam Kwon
- Division of Software, Yonsei University, Wonju, Republic of Korea.
| | - Hyoung Churl Park
- Department of Mathematics, Yonsei University, Wonju, Republic of Korea
| | - Albert Cheto Barrera
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, 84112, USA
| | - Seward B Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Benjamin Sanchez
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, 84112, USA.
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Luo X, Wang S, Rutkove SB, Sanchez B. Nonhomogeneous volume conduction effects affecting needle electromyography: an analytical and simulation study. Physiol Meas 2021; 42:10.1088/1361-6579/ac38c0. [PMID: 34763321 PMCID: PMC8744488 DOI: 10.1088/1361-6579/ac38c0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 11/11/2021] [Indexed: 12/30/2022]
Abstract
Objective.Needle electromyography (EMG) is used to study the electrical behavior of myofiber properties in patients with neuromuscular disorders. However, due to the complexity of electrical potential spatial propagation in nonhomogeneous diseased muscle, a comprehensive understanding of volume conduction effects remains elusive. Here, we develop a framework to study the conduction effect of extracellular abnormalities and electrode positioning on extracellular local field potential (LFP) recordings.Methods.The framework describes the macroscopic conduction of electrical potential in an isotropic, nonhomogeneous (i.e. two tissue) model. Numerical and finite element model simulations are provided to study the conduction effect in prototypical monopolar EMG measurements.Results.LFPs recorded are influenced in amplitude, phase and duration by the electrode position in regards to the vicinity of tissue with different electrical properties.Conclusion.The framework reveals the influence of multiple mechanisms affecting LFPs including changes in the distance between the source-electrode and tissue electrical properties.Clinical significance.Our modeled predictions may lead to new ways for interpreting volume conduction effects on recorded EMG activity, for example in neuromuscular diseases that cause structural and compositional changes in muscle tissue. These change will manifest itself by changing the electric properties of the conductor media and will impact recorded potentials in the area of affected tissue.
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Affiliation(s)
- Xuesong Luo
- Department of Automation Science and Electric Engineering, Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Beihang University, Beijing 100083, China
- Sanchez Research Lab, Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112-9206, USA
| | - Shaoping Wang
- Department of Automation Science and Electric Engineering, Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Beihang University, Beijing 100083, China
| | - Seward B. Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Benjamin Sanchez
- Sanchez Research Lab, Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112-9206, USA
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Pandeya SR, Nagy JA, Riveros D, Semple C, Taylor RS, Mortreux M, Sanchez B, Kapur K, Rutkove SB. Estimating myofiber cross-sectional area and connective tissue deposition with electrical impedance myography: A study in D2-mdx mice. Muscle Nerve 2021; 63:941-950. [PMID: 33759456 PMCID: PMC8883327 DOI: 10.1002/mus.27240] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 03/19/2021] [Indexed: 12/14/2022]
Abstract
INTRODUCTION Surface electrical impedance myography (sEIM) has the potential for providing information on muscle composition and structure noninvasively. We sought to evaluate its use to predict myofiber size and connective tissue deposition in the D2-mdx model of Duchenne muscular dystrophy (DMD). METHODS We applied a prediction algorithm, the least absolute shrinkage and selection operator, to select specific EIM measurements obtained with surface and ex vivo EIM data from D2-mdx and wild-type (WT) mice (analyzed together or separately). We assessed myofiber cross-sectional area histologically and hydroxyproline (HP), a surrogate measure for connective tissue content, biochemically. RESULTS Using WT and D2-mdx impedance values together in the algorithm, sEIM gave average root-mean-square errors (RMSEs) of 26.6% for CSA and 45.8% for HP, which translate into mean errors of ±363 μm2 for a mean CSA of 1365 μm2 and of ±1.44 μg HP/mg muscle for a mean HP content of 3.15 μg HP/mg muscle. Stronger predictions were obtained by analyzing sEIM data from D2-mdx animals alone (RMSEs of 15.3% for CSA and 34.1% for HP content). Predictions made using ex vivo EIM data from D2-mdx animals alone were nearly equivalent to those obtained with sEIM data (RMSE of 16.59% for CSA), and slightly more accurate for HP (RMSE of 26.7%). DISCUSSION Surface EIM combined with a predictive algorithm can provide estimates of muscle pathology comparable to values obtained using ex vivo EIM, and can be used as a surrogate measure of disease severity and progression and response to therapy.
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Affiliation(s)
- Sarbesh R. Pandeya
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Janice A. Nagy
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Daniela Riveros
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Carson Semple
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Rebecca S. Taylor
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Marie Mortreux
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Benjamin Sanchez
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah
| | - Kush Kapur
- Department of Neurology, Boston Childrenʼs Hospital, Harvard Medical School, Boston, Massachusetts
| | - Seward B. Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
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Luo X, Sanchez B. In silicomuscle volume conduction study validates in vivomeasurement of tongue volume conduction properties using a user tongue array depressor. Physiol Meas 2021; 42. [PMID: 33690188 DOI: 10.1088/1361-6579/abed36] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 03/09/2021] [Indexed: 01/24/2023]
Abstract
Objective.Electrophysiological assessment of the tongue volume conduction properties (VCPs) using our novel multi-electrode user tongue array (UTA) depressor has the promise to serve as a biomarker in patients with bulbar dysfunction. However, whetherin vivodata collected using the UTA depressor accurately reflect the tongue VCPs remains unknown.Approach.To address this question, we performedin silicosimulations of the depressor with an accurate anatomical tongue finite element model (FEM) using healthy human tongue VCP values, namely the conductivity and the relative permittivity, in the sagittal plane (i.e. longitudinal direction) and axial and coronal planes (i.e. transverse directions). We then established the relationship between tongue VCP values simulated from our model to measured human data.Main results.Experimental versus simulated tongue VCP values including their spatial variation were in good agreement with differences well within the variability of the experimental results. Tongue FEM simulations corroborate the feasibility of our UTA depressor in assessing tongue VCPs.Significance.The UTA depressor is a new non-invasive and safe tool to measure tongue VCPs. These electrical properties reflect the tongue's ionic composition and cellular membrane integrity and could serve as a novel electrophysiological biomarker in neurological disorders affecting the tongue.
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Affiliation(s)
- Xuesong Luo
- Sanchez Research Lab, Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112-9206, United States of America
| | - Benjamin Sanchez
- Sanchez Research Lab, Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112-9206, United States of America
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Clark BC, Rutkove S, Lupton EC, Padilla CJ, Arnold WD. Potential Utility of Electrical Impedance Myography in Evaluating Age-Related Skeletal Muscle Function Deficits. Front Physiol 2021; 12:666964. [PMID: 34025454 PMCID: PMC8138591 DOI: 10.3389/fphys.2021.666964] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/13/2021] [Indexed: 12/19/2022] Open
Abstract
Skeletal muscle function deficits associated with advancing age are due to several physiological and morphological changes including loss of muscle size and quality (conceptualized as a reduction in the intrinsic force-generating capacity of a muscle when adjusted for muscle size). Several factors can contribute to loss of muscle quality, including denervation, excitation-contraction uncoupling, increased fibrosis, and myosteatosis (excessive levels of inter- and intramuscular adipose tissue and intramyocellular lipids). These factors also adversely affect metabolic function. There is a major unmet need for tools to rapidly and easily assess muscle mass and quality in clinical settings with minimal patient and provider burden. Herein, we discuss the potential for electrical impedance myography (EIM) as a tool to evaluate muscle mass and quality in older adults. EIM applies weak, non-detectible (e.g., 400 μA), mutifrequency (e.g., 1 kHz–1 MHz) electrical currents to a muscle (or muscle group) through two excitation electrodes, and resulting voltages are measured via two sense electrodes. Measurements are fast (~5 s/muscle), simple to perform, and unaffected by factors such as hydration that may affect other simple measures of muscle status. After nearly 2 decades of study, EIM has been shown to reflect muscle health status, including the presence of atrophy, fibrosis, and fatty infiltration, in a variety of conditions (e.g., developmental growth and maturation, conditioning/deconditioning, and obesity) and neuromuscular diseases states [e.g., amyotrophic lateral sclerosis (ALS) and muscular dystrophies]. In this article, we describe prior work and current evidence of EIM’s potential utility as a measure of muscle health in aging and geriatric medicine.
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Affiliation(s)
- Brian C Clark
- Ohio Musculoskeletal and Neurological Institute (OMNI), Ohio University, Athens, OH, United States.,Department of Biomedical Sciences, Ohio University, Athens, OH, United States.,Division of Geriatric Medicine, Ohio University, Athens, OH, United States
| | - Seward Rutkove
- Department of Neurology, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA, United States
| | | | - Carlos J Padilla
- Department of Neurology, Ohio State University, Columbus, OH, United States
| | - W David Arnold
- Department of Neurology, Ohio State University, Columbus, OH, United States
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Cardoner MMDM, Kwon H, Pulido HVG, Nagy J, Rutkove S, Sanchez B. Modeling and Reproducibility of Twin Concentric Electrical Impedance Myography. IEEE Trans Biomed Eng 2021; 68:3068-3077. [PMID: 33661730 DOI: 10.1109/tbme.2021.3063724] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
OBJECTIVE Electrical impedance myography (EIM) is a recent technology to assess muscle health. As of today, the clinical application of EIM has been applied only to evaluate muscle condition using non-invasive surface electrodes in contact with the skin; however, intermediate tissues at the recording site introduce confounding artifacts which reduce the technique's performance as a biomarker of neuromuscular disorders (NMD). Here, we develop and test in humans a new approach using two concentric needles for intramuscular EIM recordings. METHODS First, we study the recording characteristics of dual concentric needle EIM via analytical models and finite element models (FEMs). Next, the validity of the models is verified by performing experiments on saline and agar phantoms. Finally, 8 subjects with various neuromuscular diseases were studied measuring tibialis anterior, biceps, deltoid, adductor pollicis brevis, first dorsal interosseous and flexor carpi radialis muscles. RESULTS Analytical and FEM simulations are in good agreement with a maximum experimental discrepancy 8% and 9% using gauge needles 26 and 30, respectively. The inter-session reproducibility, as measured by the intraclass correlation coefficients for all muscles studied, was 0.926, which is comparable or exceeds the reproducibility of other well-established electrophysiological tests to assess muscle health. CONCLUSION The reproducibility of the technique support future clinical validation of needle EIM for assessment of disease status, either as part of standard patient care or as biomarker measure in clinical trials. SIGNIFICANCE Needle EIM has the potential of becoming a valuable diagnostic tool to evaluate NMD in adult population.
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Luo X, Victoria Gutierrez Pulido H, Rutkove S, Sanchez B. A Bioimpedance-Based Device to Assess the Volume Conduction Properties of the Tongue in Neurological Disorders Affecting Bulbar function. IEEE OPEN JOURNAL OF ENGINEERING IN MEDICINE AND BIOLOGY 2021; 2:278-285. [PMID: 35402988 PMCID: PMC8940204 DOI: 10.1109/ojemb.2021.3117871] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 10/01/2021] [Accepted: 10/01/2021] [Indexed: 12/03/2022] Open
Abstract
Goal: Current instruments for bulbar assessment exhibit technical limitations that hinder the execution of clinical studies. The volume conduction properties (VCP) of the tongue reflect ionic content and myofiber integrity and they can serve as a new biomarker for evaluating neurological disorders with bulbar dysfunction. Methods: We designed a standalone bioimpedance measurement system that enables accurate, multi-frequency measurement of tongue anisotropic VCP including conductivity and relative permittivity. The system includes a tongue depressor with 16 non-invasive surface sensors for electrical contact with the tongue at directions 0\documentclass[12pt]{minimal}
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}{}$^{\circ }$\end{document}. The depressor is interfaced with the tongue electronic system with Bluetooth connectivity, and a smartphone application. De-identified patient data is sent by email. Results: We first determined the accuracy of the hardware performing phantom measurements mimicking a broad range of tongue values and determined the error to be \documentclass[12pt]{minimal}
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}{}$< $\end{document}1%. We then validated our new technology measuring a cohort of 7 healthy human subjects under Institutional Review Board approval. Conclusions: None of the subjects who participated suffered discomfort or gag reflexes. The novel technique presented for intra-oral assessment of tongue VCP provides standard, objective and quantitative data potentially sensitive to alterations in tongue internal structure and composition.
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Affiliation(s)
- Xuesong Luo
- Sanchez Research Lab, Department of Electrical and Computer EngineeringUniversity of Utah Salt Lake City UT 84112 USA
| | | | - Seward Rutkove
- Department of Neurology, Beth Israel Deaconess Medical CenterHarvard Medical School Boston MA 02115 USA
| | - Benjamin Sanchez
- Sanchez Research Lab, Department of Electrical and Computer EngineeringUniversity of Utah Salt Lake City UT 84112 USA
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In vivo muscle conduction study of the tongue using a multi-electrode tongue depressor. Clin Neurophysiol 2020; 132:683-687. [PMID: 33309468 DOI: 10.1016/j.clinph.2020.11.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 10/08/2020] [Accepted: 11/10/2020] [Indexed: 12/13/2022]
Abstract
OBJECTIVE To test a novel technology for assessment of the volume conduction properties (VCPs) of the tongue. These properties are electrophysiological data that might reflect alterations in patients with tongue involvement. METHODS Seven healthy individuals were self-measured. The depressor was placed on the surface of the anterior tongue. Directional differences of VCPs were determined with standard descriptive statistics. RESULTS Conductivity in longitudinal direction was larger than in transverse direction at 16 (p < 0.05), 32 (p < 0.05), 64 (p < 0.01), and 128 kHz (p < 0.01). No differences were found in relative permittivity. The intraclass correlation was 0.778 and 0.771, respectively. CONCLUSIONS Our technology provides, for the first time, VCPs of the healthy human tongue. SIGNIFICANCE Tongue VCPs are standard electrophysiological, quantitative and objective data reflecting ionic content and membrane integrity which could find value for diagnostic purposes and treatment monitoring.
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13
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Approaches for determining cardiac bidomain conductivity values: progress and challenges. Med Biol Eng Comput 2020; 58:2919-2935. [PMID: 33089458 DOI: 10.1007/s11517-020-02272-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 09/17/2020] [Indexed: 10/23/2022]
Abstract
Modelling the electrical activity of the heart is an important tool for understanding electrical function in various diseases and conduction disorders. Clearly, for model results to be useful, it is necessary to have accurate inputs for the models, in particular the commonly used bidomain model. However, there are only three sets of four experimentally determined conductivity values for cardiac ventricular tissue and these are inconsistent, were measured around 40 years ago, often produce different results in simulations and do not fully represent the three-dimensional anisotropic nature of cardiac tissue. Despite efforts in the intervening years, difficulties associated with making the measurements and also determining the conductivities from the experimental data have not yet been overcome. In this review, we summarise what is known about the conductivity values, as well as progress to date in meeting the challenges associated with both the mathematical modelling and the experimental techniques. Graphical abstract Epicardial potential distributions, arising from a subendocardial ischaemic region, modelled using conductivity data from the indicated studies.
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Rutkove SB, Sanchez B. Electrical Impedance Methods in Neuromuscular Assessment: An Overview. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a034405. [PMID: 30291145 DOI: 10.1101/cshperspect.a034405] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Electrical impedance methods have been used as evaluation tools in biological and medical science for well over 100 years. However, only recently have these techniques been applied specifically to the evaluation of conditions affecting nerve and muscle. This specific application, termed electrical impedance myography (EIM), is finding wide application as it can provide a quantitative index of muscle condition that can assist with diagnosis, track disease progression, and assess the beneficial impact of therapy. Using noninvasive surface methods, EIM has been studied in a number of conditions ranging from amyotrophic lateral sclerosis to muscular dystrophy to disuse atrophy. Data support that the technique is sensitive to disease status and can offer the possibility of performing clinical trials with fewer subjects than would otherwise be possible. Recent advances in the field include improved approaches for using EIM as a "virtual biopsy" and the development of combined needle impedance-electromyography technology.
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Affiliation(s)
- Seward B Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
| | - Benjamin Sanchez
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
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15
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Kwon H, de Morentin MM, Nagy JA, Rutkove SB, Sanchez B. Approximate complex electrical potential distribution in the monodomain model with unequal conductivity and relative permittivity anisotropy ratios. Physiol Meas 2019; 40:085008. [PMID: 31408853 DOI: 10.1088/1361-6579/ab3aa1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Electrical conductivity and relative permittivity are properties that indicate muscle health and they have different values parallel and perpendicular to the direction of the myofiber, a concept known as anisotropy. When the intrinsic electrical properties of muscle have ratios of anisotropy that are different then there is no analytical solution that can describe the electrical potential distribution in the tissue. APPROACH Here, we present approximate analytical solutions to monodomain equations with unequal anisotropy ratios. For this, we base our analysis on perturbation theory where the electrical potential is approximated by the sum of the zeroth- and first-order terms of an infinite series. MAIN RESULTS The validity of the approach is confirmed using experimental data for healthy and diseased muscle available online. SIGNIFICANCE A better understanding of electrical potential distribution in anisotropic skeletal muscle tissue will allow the development of improved diagnostic tools for neuromuscular diseases.
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Affiliation(s)
- H Kwon
- College of Science and Technology, Yonsei University, Wonju 26493, Republic of Korea
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Kwon H, Guasch M, Nagy JA, Rutkove SB, Sanchez B. New electrical impedance methods for the in situ measurement of the complex permittivity of anisotropic skeletal muscle using multipolar needles. Sci Rep 2019; 9:3145. [PMID: 30816169 PMCID: PMC6395651 DOI: 10.1038/s41598-019-39277-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 01/21/2019] [Indexed: 01/24/2023] Open
Abstract
This paper provides a rigorous analysis on the measurement of the permittivity of two-dimensional anisotropic biological tissues such as skeletal muscle using the four-electrode impedance technique. The state-of-the-art technique requires individual electrodes placed at the same depth in contact with the anisotropic material, e.g. using monopolar needles. In this case, the minimum of measurements in different directions needed to estimate the complex permittivity and its anisotropy direction is 3, which translates into 12 monopolar needle insertions (i.e. 3 directions × 4 electrodes in each direction). Here, we extend our previous work and equip the reader with 8 new methods for multipolar needles, where 2 or more electrodes are spaced along the needle's shaft in contact with the tissue at different depths. Using multipolar needles, the new methods presented reduce the number of needle insertions by a factor of 2 with respect to the available methods. We illustrate the methods with numerical simulations and new experiments on ex vivo ovine skeletal muscle (n = 3). Multi-frequency longitudinal and transverse permittivity data from 30 kHz to 1 MHz is made publicly available in the supplementary material. The methods presented here for multipolar needles bring closer the application of needle electrical impedance to patients with neuromuscular diseases.
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Affiliation(s)
- H Kwon
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215-5491, USA. .,College of Science of & Technology, Yonsei University, Wonju, 26493, Republic of Korea.
| | - M Guasch
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215-5491, USA
| | - J A Nagy
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215-5491, USA
| | - S B Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215-5491, USA
| | - B Sanchez
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215-5491, USA.
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Rutkove SB, Kwon H, Guasch M, Wu JS, Sanchez B. Electrical impedance imaging of human muscle at the microscopic scale using a multi-electrode needle device: A simulation study. Clin Neurophysiol 2018; 129:1704-1708. [PMID: 29804914 DOI: 10.1016/j.clinph.2018.04.746] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 03/23/2018] [Accepted: 04/29/2018] [Indexed: 12/14/2022]
Abstract
OBJECTIVE To use a standard modeling approach to evaluate the feasibility of imaging healthy and diseased skeletal muscle at the microscopic scale with a novel electrical impedance imaging (EII) needle. METHODS We modeled an EII needle containing 16 impedance electrodes arranged circumferentially around the shaft of a non-conductive 19-gauge needle in 4 planes. We then combined the finite element method approach with a reconstruction algorithm to create imaging simulations of the electrical properties of the triceps brachii by localized intramuscular fat (as might be seen in any chronic neuromuscular disease) and by localized edema (as in inflammatory myositis or after direct muscle injury). RESULTS We were able to image a 1 cm radial region of interest with a resolution of 200 µm. Modeling localized deposition of fat and pockets of inflammatory cells, showing clear differences between the two modeled clinical states. CONCLUSIONS This modeling study shows needle EII's ability to image the internal composition of muscle. These results can serve as an initial guide in designing and manufacturing prototype EII needles for experimental testing in animals and eventually in humans. SIGNIFICANCE Needle EII could serve as a new minimally invasive technique for imaging human muscle at the microscopic scale, potentially serving as a new biomarker to assess disease response to therapy.
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Affiliation(s)
- Seward B Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, USA
| | - Hyeuknam Kwon
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, USA
| | - Maria Guasch
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, USA
| | - Jim S Wu
- Department Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, USA
| | - Benjamin Sanchez
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, USA.
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Kwon H, Malik WQ, Rutkove SB, Sanchez B. Separation of Subcutaneous Fat From Muscle in Surface Electrical Impedance Myography Measurements Using Model Component Analysis. IEEE Trans Biomed Eng 2018; 66:354-364. [PMID: 29993468 DOI: 10.1109/tbme.2018.2839977] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE Electrical impedance myography (EIM) is a relatively new technique to assess neuromuscular disorders (NMD). Although the application of EIM using surface electrodes (sEIM) has been adopted by the neurology community in recent years to evaluate NMD status, sEIM's sensitivity as a biomarker of skeletal muscle condition is impacted by subcutaneous fat (SF) tissue. Here, we develop a method that is able to remove the contribution of SF from sEIM data. METHODS We evaluate independent component analysis (ICA) and principal component analysis (PCA) for this purpose. Then, we introduce the so-called model component analysis (MCA). All methods are validated with numerical simulations using impedivity data from SF and muscle tissues. The methods are then tested with measurements performed in diseased individuals ( n=3). RESULTS Simulations demonstrate that MCA is the most accurate method at separating the impedivity of SF and muscle tissues with the accuracy being 99.2%, followed by ICA with 51.4%, and finally PCA with 38.5%. Experimental results from sEIM data measured on the triceps brachii of patients are consistent with muscle grayscale level values obtained using ultrasound imaging. CONCLUSION MCA can be used to separate the impedivity of SF and muscle tissues from sEIM data, thus increasing the sensitivity to detect changes in the muscle. SIGNIFICANCE MCA can make the sEIM technique a better diagnostic tool and biomarker of disease progression and response to therapy by removing the confounding effect of SF tissue in NMD patients with excess subcutaneous fat tissue for any reason.
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Kwon H, Di Cristina JF, Rutkove SB, Sanchez B. Recording characteristics of electrical impedance-electromyography needle electrodes. Physiol Meas 2018; 39:055005. [PMID: 29616985 DOI: 10.1088/1361-6579/aabb8c] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Needle EMG remains the standard clinical test for neuromuscular disease (NMD) assessment, but it only characterizes myofiber membrane depolarization. On the other hand, electrical impedance provides non-electrically active structural and compositional data of tissues. Here, we designed a prototype of needle electrode integrating electrical impedance and EMG measurement capabilities, the so-called I-EMG needle electrode. APPROACH We use finite element method models to study the impedance recording characteristics of I-EMG needle electrodes. The simulated electrical and mechanical design specifications are then manufactured to create a prototype of an I-EMG needle electrode. We pilot these new needle electrodes by conducting in vivo impedance measurements with muscle at rest on healthy wild-type (wt, n = 5) and muscular dystrophy (mdx, n = 5) mice. Comparisons between wt and mdx mice are performed using Mann-Whitney test, two-tailed, p < 0.05. The electrical characterization of the EMG electrode in the developed I-EMG needles was performed in vitro on saline solution and through EMG detection in wt animal at rest and during voluntary contractions. RESULTS Muscle impedance demonstrate good repeatability (p < 0.05 and p < 0.005 for resistance and reactance at 50 kHz, respectively) and agreement between different I-EMG needles. Impedance data allows us to discriminate between mdx and wt muscle (p < 0.05 and p < 0.005 for resistance and reactance at 10 kHz, respectively). EMG broadband noise power and peak amplitude using the I-EMG needle were similar to that of a commercial monopolar EMG needle. EMG recordings using the I-EMG needle measured electrical activity similar to a standard monopolar needle with muscle at rest and during voluntary contraction. SIGNIFICANCE Needle I-EMG technology may offer the opportunity to enhance the diagnostic capability and quantification of NMD beyond that possible with either impedance or EMG techniques separately. Ultimately, needle I-EMG could serve as a new bedside tool to assess NMD without increasing the complexity or duration of the EMG test.
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Affiliation(s)
- H Kwon
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, United States of America
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