Optically pumped magnetometers disclose magnetic field components of the muscular action potential

Broser, Philip J.; Middelmann, Thomas; Sometti, Davide; Braun, Christoph

doi:10.1101/2020.07.30.228882

Cited by 3 publications

(6 citation statements)

References 17 publications

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“…As experimentally measured by Broser et al. ( 2021 ), the proposed model predicts a triphasic shape of the overall magnetic muscle action potential caused by volume currents in the extracellular space. However, as volume currents strongly depend on the exact muscle geometry, a direct comparison to the experiments of Broser et al.…”

Section: Discussionsupporting

confidence: 60%

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Investigating the spatial resolution of EMG and MMG based on a systemic multi-scale model

Klotz

Gizzi

Röhrle

2022

Biomech Model Mechanobiol

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While electromyography (EMG) and magnetomyography (MMG) are both methods to measure the electrical activity of skeletal muscles, no systematic comparison between both signals exists. Within this work, we propose a novel in silico model for EMG and MMG and test the hypothesis that MMG surpasses EMG in terms of spatial selectivity, i.e. the ability to distinguish spatially shifted sources. The results show that MMG provides a slightly better spatial selectivity than EMG when recorded directly on the muscle surface. However, there is a remarkable difference in spatial selectivity for non-invasive surface measurements. The spatial selectivity of the MMG components aligned with the muscle fibres and normal to the body surface outperforms the spatial selectivity of surface EMG. Particularly, for the MMG’s normal-to-the-surface component the influence of subcutaneous fat is minimal. Further, for the first time, we analyse the contribution of different structural components, i.e. muscle fibres from different motor units and the extracellular space, to the measurable biomagnetic field. Notably, the simulations show that for the normal-to-the-surface MMG component, the contribution from volume currents in the extracellular space and in surrounding inactive tissues, is negligible. Further, our model predicts a surprisingly high contribution of the passive muscle fibres to the observable magnetic field.

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Section: Discussionsupporting

confidence: 60%

“…For example, Broser et al. ( 2021 ) used a finite wire model to infer from their measurements the underling physiology. However, this approach could not explain some of their experimental observations.…”

Section: Introductionmentioning

confidence: 99%

Investigating the spatial resolution of EMG and MMG based on a systemic multi-scale model

Klotz

Gizzi

Röhrle

2022

Biomech Model Mechanobiol

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“…QuSpin OPM sensors are conformal with a 6.5 mm sensor stand-off that in aggregate contribute to an improved magnetic signal-to-noise ratio therefore capable of surpassing current SQUID sensor technology due to closer proximity to the neuronal source (Iivanainen et al, 2017;Hill et al, 2020). Recently Broser et.al., (Broser et al, 2018;Broser et al, 2020) showed that commercial Gen-1 OPMs (QuSpin Inc, CO, USA) detect compound muscle action currents consistent with motor neuron activation. Expounding on this work, we employed the commercially available Gen-2 OPM (QuSpin Inc, CO, USA) with the aim to measure upper extremity action currents equivalent to the SNAP and H-Reflex.…”

Section: Contribution To the Fieldmentioning

confidence: 99%

Peripheral Nerve Magnetoneurography with Optically Pumped Magnetometers

Bu¹,

Borna

Schwindt

et al. 2021

Preprint

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The pain experience is a complex process that involves the activation of multiple neuronal signaling pathways that originate in the peripheral nervous system and are transmitted to the central nervous system. In the peripheral nervous system, specialized peripheral nociceptor (unmyelinated C fibers and lightly myelinated A-Delta; fibers) depolarization results in afferent transmission of noxious signals. Small Fiber Neuropathy (SFN) can result in chronic neuropathic pain with significant lifetime morbidity if not promptly treated. Current technological and operator limitations may delay SFN diagnosis and prolong appropriate treatment. Therefore, there is an unmet need for robust and non-invasive ways to accurately measure small fiber function. It is well known that the propagation of action potentials along a nerve is the result of ionic current flow which, according to the Ampere Law, generates a small magnetic field that is detectable by magnetometers such as superconducting quantum interference device (SQUID) Magnetoencephalography (MEG) systems. Optically pumped magnetometers (OPM) are an emerging class of quantum magnetic sensors with a demonstrated sensitivity of 1 fT/SQRT;Hz level, capable of cortical action potential detection. However, they have not as of yet been implemented for peripheral nerve action potential detection. We demonstrate for the first time, compelling evidence that OPM can detect the magnetic signature of travelling peripheral nerve action potentials that indicate OPM use as a potential technique for SFN diagnosis.

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“…This yields high technical demands for MMG recording systems (Zuo et al, 2020), for example, with respect to the sensitivity, the detection range, the sampling rate, the shielding from magnetic noise, the size and portability of the sensor device as well as the cost of such recordings. Nevertheless, a few proof-of-concept studies, e. g. Broser et al (2018Broser et al ( , 2021, Llinás et al (2020), Reincke (1993), illustrate its feasibility for biomedical applications.…”

Section: Introductionmentioning

confidence: 99%

“…Common to all MMG models is that they first calculate the current field, which is then used to obtain the magnetic field. For example, Broser et al (2021) used a finite wire model to infer from their measurements the underling physi-ology. However, this approach could not explain some of their experimental observations.…”

Section: Introductionmentioning

confidence: 99%

Investigating the spatial resolution of EMG and MMG based on a systemic multi-scale model

Klotz¹,

Gizzi²,

Röhrle³

2021

Preprint

View full text Add to dashboard Cite

While electromyography (EMG) and magnetomyography (MMG) are both methods to measure the electrical activity of skeletal muscles, no systematic comparison between both signals exists. Within this work, we propose a systemic in silico model for EMG and MMG and test the hypothesis that MMG surpasses EMG in terms of spatial selectivity. The results show that MMG provides a slightly better spatial selectivity than EMG when recorded directly on the muscle surface. However, there is a remarkable difference in spatial selectivity for non-invasive surface measurements. The spatial selectivity of the MMG components aligned with the muscle fibres and normal to the body surface outperforms the spatial selectivity of surface EMG. Particularly, for the MMG's normal-to-the-surface component the influence of subcutaneous fat is minimal. Further, for the first time, we analyse the contribution of different structural components, i. e., muscle fibres from different motor units and the extracellular space, to the measurable biomagnetic field. Notably, the simulations show that the normal-to-the-surface MMG component, the contribution from volume currents in the extracellular space and in surrounding inactive tissues is neg-

show abstract

Optically pumped magnetometers disclose magnetic field components of the muscular action potential

Cited by 3 publications

References 17 publications

Investigating the spatial resolution of EMG and MMG based on a systemic multi-scale model

Investigating the spatial resolution of EMG and MMG based on a systemic multi-scale model

Peripheral Nerve Magnetoneurography with Optically Pumped Magnetometers

Investigating the spatial resolution of EMG and MMG based on a systemic multi-scale model

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