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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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Kwon H, Rojas CR, Rutkove SB, Sanchez B. Three-harmonic optimal multisine input power spectrum for bioimpedance identification. Physiol Meas 2019; 40:05NT02. [PMID: 31026854 DOI: 10.1088/1361-6579/ab1cf3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The attention towards optimal signals for measuring electrical bioimpedance (EBI) has increased recently due to the many advantages they offer such as, for example, reduced measuring time. Here, the design of a three-harmonic optimized multisine input power spectrum for measuring bioimpedance is considered. APPROACH The approach is based on designing the input power spectrum multisine excitation by optimizing a scalar function of the information matrix using the Fricke-Morse model. MAIN RESULTS Simple analytical equations are provided that can be adopted by the reader to optimize the multisine input power spectrum to satisfy any specific application-related EBI measurement. SIGNIFICANCE The presented signal may be a good choice of excitation signal in EBI applications where optimal excitation power spectrum is desired.
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Affiliation(s)
- H Kwon
- College of Science & Technology, Yonsei University, Wonju 26493, Republic of Korea
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Balleza-Ordaz M, Estrella-Cerón R, Romero-Muñiz T, Vargas-Luna M. Lung ventilation monitoring by electrical bioimpedance technique using three different 4-electrode thoracic configurations: Variability of calibration equations. Biomed Signal Process Control 2019. [DOI: 10.1016/j.bspc.2018.08.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Louarroudi E, Sanchez B. Reply to Comment on 'On the correct use of stepped-sine excitations for the measurement and identification of time-varying bioimpedance'. Physiol Meas 2018; 39:028002. [PMID: 29376499 DOI: 10.1088/1361-6579/aaab0b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The authors Lang and Zalka commented on our previous note (Louarroudi and Sanchez 2017 Physiol. Meas. 38 N73-80), indicating interpolation as a suitable method to estimate the instantaneous impedance of a time-varying impedance from stepped-sine excitations. APPROACH Here, we briefly delve into the underlying assumptions of the interpolation scheme. MAIN RESULTS We illustrate the approximation of the instantaneous impedance of a time-varying impedance from stepped-sine measurements conducting experiments on a phantom. SIGNIFICANCE We outline the technical challenges awaiting future research required to validate the accuracy of the instantaneous impedance approximation of a time-varying impedance using stepped-sine excitations.
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Affiliation(s)
- E Louarroudi
- Department of Neurology, Division of Neuromuscular Diseases, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Harvard Medical School, Boston, MA 02215-5491, United States of America
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Ojarand J, Min M. On the Selection of Excitation Signals for the Fast Spectroscopy of Electrical Bioimpedance. JOURNAL OF ELECTRICAL BIOIMPEDANCE 2018; 9:133-141. [PMID: 33584929 PMCID: PMC7852012 DOI: 10.2478/joeb-2018-0018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Indexed: 06/12/2023]
Abstract
Different excitation signals are applicable in the wideband impedance spectroscopy in general. However, in electrical bioimpedance (EBI) measurements, there are limitations that set specific demands on the properties of the excitation signals. This paper compares the efficiency of different excitation signals in a graspable presentation and gives recommendations for their use. More exactly, the paper deals with finding the efficient excitation waveforms for the fast spectroscopy of electrical bioimpedance. Nevertheless, the described solutions could be useful also in other implementations of impedance spectroscopy intended for frequency domain characterization of different objects.
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Affiliation(s)
- Jaan Ojarand
- Thomas Johann Seebeck Department of Electronics, Tallinn University of Technology, Tallinn, EstoniaUnited Kingdom
| | - Mart Min
- Thomas Johann Seebeck Department of Electronics, Tallinn University of Technology, Tallinn, EstoniaUnited Kingdom
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Sanchez B, Rutkove SB. Electrical Impedance Myography and Its Applications in Neuromuscular Disorders. Neurotherapeutics 2017; 14:107-118. [PMID: 27812921 PMCID: PMC5233633 DOI: 10.1007/s13311-016-0491-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Electrical impedance myography (EIM) refers to the specific application of electrical bioimpedance techniques for the assessment of neuromuscular disorders. In EIM, a weak, high-frequency electrical current is applied to a muscle or muscle group of interest and the resulting voltages measured. Among its advantages, the technique can be used noninvasively across a variety of disorders and requires limited subject cooperation and evaluator training to obtain accurate and repeatable data. Studies in both animals and human subjects support its potential utility as a primary diagnostic tool, as well as a biomarker for clinical trial or individual patient use. This review begins by providing an overview of the current state and technological advances in electrical impedance myography and its specific application to the study of muscle. We then provide a summary of the clinical and preclinical applications of EIM for neuromuscular conditions, and conclude with an evaluation of ongoing research efforts and future developments.
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Affiliation(s)
- Benjamin Sanchez
- Department of Neurology, Division of Neuromuscular Disease, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Seward B Rutkove
- Department of Neurology, Division of Neuromuscular Disease, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA.
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Louarroudi E, Sanchez B. On the correct use of stepped-sine excitations for the measurement of time-varying bioimpedance. Physiol Meas 2016; 38:N73-N80. [PMID: 28005012 DOI: 10.1088/1361-6579/aa556d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE When a linear time-varying (LTV) bioimpedance is measured using stepped-sine excitations, a compromise must be made: the temporal distortions affecting the data depend on the experimental time, which in turn sets the data accuracy and limits the temporal bandwidth of the system that needs to be measured. APPROACH Here, the experimental time required to measure linear time-invariant bioimpedance with a specified accuracy is analyzed for different stepped-sine excitation setups. RESULTS We provide simple equations that allow the reader to know whether LTV bioimpedance can be measured through repeated time- invariant stepped-sine experiments. SIGNIFICANCE Bioimpedance technology is on the rise thanks to a plethora of healthcare monitoring applications. The results presented can help to avoid distortions in the data while measuring accurately non-stationary physiological phenomena. The impact of the work presented is broad, including the potential of enhancing bioimpedance studies and healthcare devices using bioimpedance technology.
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Affiliation(s)
- E Louarroudi
- Optical Metrology, 3D design and Mechanics (Op3Mech) Research Group, Faculty of Applied Engineering, University of Antwerp, 2020 Antwerp, Belgium
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Moorman R, Simmons M. Martin Black award for the best paper published in 2015. Physiol Meas 2016; 37:E27-E28. [PMID: 27754985 DOI: 10.1088/0967-3334/37/11/e27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Orschulik J, Petkau R, Wartzek T, Hochhausen N, Czaplik M, Leonhardt S, Teichmann D. Improved electrode positions for local impedance measurements in the lung-a simulation study. Physiol Meas 2016; 37:2111-2129. [PMID: 27811407 DOI: 10.1088/0967-3334/37/12/2111] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Impedance spectroscopy can be used to analyze the dielectric properties of various materials. In the biomedical domain, it is used as bioimpedance spectroscopy (BIS) to analyze the composition of body tissue. Being a non-invasive, real-time capable technique, it is a promising modality, especially in the field of lung monitoring. Unfortunately, up to now, BIS does not provide any regional lung information as the electrodes are usually placed in hand-to-hand or transthoracic configurations. Even though transthoracic electrode configurations are in general capable of monitoring the lung, no focusing to specific regions is achieved. In order to resolve this issue, we use a finite element model (FEM) of the human body to study the effect of different electrode configurations on measured BIS data. We present evaluation results and show suitable electrode configurations for eight lung regions. We show that, using these optimized configurations, BIS measurements can be focused to desired regions allowing local lung analysis.
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Affiliation(s)
- Jakob Orschulik
- Philips Chair for Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Aachen, Germany
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Rababah AS, Walsh SJ, Manoharan G, Walsh PR, Escalona OJ. Intracardiac impedance response during acute AF internal cardioversion using novel rectilinear and capacitor-discharge waveforms. Physiol Meas 2016; 37:1129-45. [PMID: 27328164 DOI: 10.1088/0967-3334/37/7/1129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Intracardiac impedance (ICI) is a major determinant of success during internal cardioversion of atrial fibrillation (AF). However, there have been few studies that have examined the dynamic behaviour of atrial impedance during internal cardioversion in relation to clinical outcome. In this study, voltage and current waveforms captured during internal cardioversion of acute AF in ovine models using novel radiofrequency (RF) generated low-tilt rectilinear and conventional capacitor-discharge based shock waveforms were retrospectively analysed using a digital signal processing algorithm to investigate the dynamic behaviour of atrial impedance during cardioversion. The algorithm was specifically designed to facilitate the simultaneous analysis of multiple impedance parameters, including: mean intracardiac impedance (Z M), intracardiac impedance variance (ICIV) and impedance amplitude spectrum area (IAMSA) for each cardioversion event. A significant reduction in ICI was observed when comparing two successive shocks of increasing energy where cardioversion outcome was successful. In addition, ICIV and IAMSA variables were found to inversely correlate to the magnitude of energy delivered; with a stronger correlation found to the former parameter. In conclusion, ICIV and IAMSA have been evidenced as two key dynamic intracardiac impedance variables that may prove useful in better understanding of the cardioversion process and that could potentially act as prognostic markers with respect to clinical outcome.
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Affiliation(s)
- A S Rababah
- School of Engineering, Engineering Research Institute, Ulster University, Newtownabbey, UK
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Sanchez B, Louarroudi E, Rutkove SB, Pintelon R. Circular motion analysis of time-varying bioimpedance. Physiol Meas 2015; 36:2353-67. [PMID: 26489699 DOI: 10.1088/0967-3334/36/11/2353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This paper presents a step forward towards the analysis of a linear periodically time-varying (PTV) bioimpedance ZPTV(jw, t), which is an important subclass of a linear time-varying (LTV) bioimpedance. Similarly to the Fourier coefficients of a periodic signal, a PTV impedance can be decomposed into frequency dependent impedance phasors, [Formula: see text], that are rotating with an angular speed of wr = 2πr/TZ. The vector length of these impedance phasors corresponds to the amplitude of the rth-order harmonic impedance |Zr( jw)| and the initial phase is given by Φr(w, t0) = [Symbol: see text]Zr( jw) + 2πrt0/TZ, with t0∈[0, T] being a time instant within the measurement time T. The impedance period TZ stands for the cycle length of the bio-system under investigation; for example, the elapsed time between two consecutive R-waves in the electrocardiogram or the breathing periodicity in case of the heart or lungs, respectively. First, it is demonstrated that the harmonic impedance phasor [Formula: see text], at a particular measured frequency k, can be represented by a rotating phasor, leading to the so-called circular motion analysis technique. Next, the two dimensional (2D) representation of the harmonic impedance phasors is then extended to a three-dimensional (3D) coordinate system by taking into account the frequency dependence. Finally, we introduce a new visualizing tool to summarize the frequency response behavior of ZPTV( jw, t) into a single 3D plot using the local Frenet-Serret frame. This novel 3D impedance representation is then compared with the 3D Nyquist representation of a PTV impedance. The concepts are illustrated through real measurements conducted on a PTV RC-circuit.
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Affiliation(s)
- B Sanchez
- Department of Neurology, Division of Neuromuscular Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, USA
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Sanchez B, Li J, Yim S, Pacheck A, Widrick JJ, Rutkove SB. Evaluation of Electrical Impedance as a Biomarker of Myostatin Inhibition in Wild Type and Muscular Dystrophy Mice. PLoS One 2015; 10:e0140521. [PMID: 26485280 PMCID: PMC4618134 DOI: 10.1371/journal.pone.0140521] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 09/28/2015] [Indexed: 12/14/2022] Open
Abstract
Objectives Non-invasive and effort independent biomarkers are needed to better assess the effects of drug therapy on healthy muscle and that affected by muscular dystrophy (mdx). Here we evaluated the use of multi-frequency electrical impedance for this purpose with comparison to force and histological parameters. Methods Eight wild-type (wt) and 10 mdx mice were treated weekly with RAP-031 activin type IIB receptor at a dose of 10 mg kg−1 twice weekly for 16 weeks; the investigators were blinded to treatment and disease status. At the completion of treatment, impedance measurements, in situ force measurements, and histology analyses were performed. Results As compared to untreated animals, RAP-031 wt and mdx treated mice had greater body mass (18% and 17%, p < 0.001 respectively) and muscle mass (25% p < 0.05 and 22% p < 0.001, respectively). The Cole impedance parameters in treated wt mice, showed a 24% lower central frequency (p < 0.05) and 19% higher resistance ratio (p < 0.05); no significant differences were observed in the mdx mice. These differences were consistent with those seen in maximum isometric force, which was greater in the wt animals (p < 0.05 at > 70 Hz), but not in the mdx animals. In contrast, maximum force normalized by muscle mass was unchanged in the wt animals and lower in the mdx animals by 21% (p < 0.01). Similarly, myofiber size was only non-significantly higher in treated versus untreated animals (8% p = 0.44 and 12% p = 0.31 for wt and mdx animals, respectively). Conclusions Our findings demonstrate electrical impedance of muscle reproduce the functional and histological changes associated with myostatin pathway inhibition and do not reflect differences in muscle size or volume. This technique deserves further study in both animal and human therapeutic trials.
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Affiliation(s)
- Benjamin Sanchez
- Department of Neurology, Division of Neuromuscular Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, United States of America
- * E-mail:
| | - Jia Li
- Department of Neurology, Division of Neuromuscular Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, United States of America
| | - Sung Yim
- Department of Neurology, Division of Neuromuscular Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, United States of America
| | - Adam Pacheck
- Department of Neurology, Division of Neuromuscular Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, United States of America
| | - Jeffrey J. Widrick
- Division of Genetics and Genomics, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02215-5491, United States of America
| | - Seward B. Rutkove
- Department of Neurology, Division of Neuromuscular Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, United States of America
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Yang Y, Wang L, Wang P, Yang X, Zhang F, Wen H, Teng Z. Design of tri-level excitation signals for broadband bioimpedance spectroscopy. Physiol Meas 2015; 36:1995-2007. [PMID: 26261063 DOI: 10.1088/0967-3334/36/9/1995] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Bioimpedance spectroscopy (BIS) measurement methods have been evolving from the traditional frequency-sweep approach to the multi-frequency simultaneous measurement technique which can drastically reduce measuring time and will be increasingly attractive for time-varying biological applications. Multi-frequency mixed (MFM) signals with sparsely distributed spectra are desirable for broadband BIS measurement. This paper proposes a synthesis method to design a series of tri-level MFM signals which contain only three values (+1, 0, -1), and has majority energy distributed on its (2(n))th primary harmonics. Tri-level MFM signals have both high energy efficiency and a low crest factor. An impedance measurement experiment excited by an 8th-order tri-level MFM signal on a RC three-element equivalent model has been performed, and the results on 8 primary harmonic frequencies ranging from 8 to 1024 kHz show a high accuracy with the mean amplitude relative error of 0.41% and mean phase absolute error of 0.18°, which has validated the feasibility of the tri-level MFM signals for broadband BIS measurement.
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Affiliation(s)
- Yuxiang Yang
- Department of Precision and Instrumentation Engineering, Xi'an University of Technology, Xi'an, People's Republic of China
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