Guidelines to electrode positioning for human and animal electrical impedance myography research.

Adam Pacheck,Seward B Rutkove,Benjamin Sanchez

doi:10.1038/srep32615

Adam Pacheck, Seward B Rutkove + Show 1 more

Open Access

https://doi.org/10.1038/srep32615

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Abstract

The positioning of electrodes in electrical impedance myography (EIM) is critical for accurately assessing disease progression and effectiveness of treatment. In human and animal trials for neuromuscular disorders, inconsistent electrode positioning adds errors to the muscle impedance. Despite its importance, how the reproducibility of resistance and reactance, the two parameters that define EIM, are affected by changes in electrode positioning remains unknown. In this paper, we present a novel approach founded on biophysical principles to study the reproducibility of resistance and reactance to electrode misplacements. The analytical framework presented allows the user to quantify a priori the effect on the muscle resistance and reactance using only one parameter: the uncertainty placing the electrodes. We also provide quantitative data on the precision needed to position the electrodes and the minimum muscle length needed to achieve a pre-specified EIM reproducibility. The results reported here are confirmed with finite element model simulations and measurements on five healthy subjects. Ultimately, our data can serve as normative values to enhance the reliability of EIM as a biomarker and facilitate comparability of future human and animal studies.

Highlights

Frequency, kHz the impedance: the resistance and reactance increase or decrease depending on the electrode’s position, and the sensitivity is different when the current source electrode moves distally or proximally
We propose the following model to analyze the effect of electrode positioning in EIM, Ze where Ze =Re +jXe is the muscle impedance measured with electrodes’ misplacements, Z =R +jX is the “error-free” muscle impedance measured with uniform electrode spacing and j is the complex imaginary unit
The effect caused by an electrode misplacement in the y-axis is lower than that in the x-axis for all deviations from even spacing. This result emphasizes the relevance of a correct positioning of the electrodes, in the main direction specified by the electrode array where the influence of an electrode positioning error on the resistance and reactance is greater

Summary

Introduction

KHz the impedance: the resistance and reactance increase or decrease depending on the electrode’s position, and the sensitivity is different when the current source electrode moves distally or proximally. The potential electrodes are placed few cm apart from the current electrodes, with the center on the mid-line between the prominent ends of the right radius and ulna of the wrist, and mid-line between the medial and lateral malleoli of the right ankle In these studies, the main objective has been to quantify the effect of a misplacement in one or more electrodes in the determination of body composition parameters. The authors placed the current electrodes on the dorsum of both hands for measuring the biceps and on the dorsum of bother feet for the tibialis anterior[28]. Our results are normalized so as to allow prediction of precision needed for positioning the electrodes in both human and animal studies to achieve a pre-specified reproducibility

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Conclusion