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Magnetic fields from skeletal muscles: a valuable physiological measurement?

Garcia MA, Baffa O - Front Physiol (2015)

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biociências da Atividade Física, Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brasil ; Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo Ribeirão Preto, Brasil.

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It is well known that whenever a motor unit is recruited, electrical, and mechanical events are generated in skeletal muscle fibers... In addition, when skeletal muscle fibers are injured, there is a leakage of current that can be easily detected by SQUIDs, which also help to better map sites of muscle lesions (Curio et al., ; Mackert et al., )... Another important issue is that the MMG signal amplitude seems to be linearly correlated with muscle force production (Rutten et al., ; Gielen et al., ) in contrast to the EMG signal that is still under discussion (Hashemi et al., )... It can be especially useful in the simplification of mathematical models with added reliability in predicting muscle force production from the MMG signal instead the EMG... Furthermore, as a superconductor device, SQUIDs require to be cooled with liquid helium, which is operationally difficult to handle and very expensive, limiting a wide use of this approach... Alternatively, few authors have also attempted to detect magnetic fields of neural and skeletal muscle fibers using magnetic resonance imaging (MRI) although they did not succeed yet (Wijesinghe and Roth, ; Roth et al., )... The skeletal muscles present a magnetic susceptibility lower when compared to other biological tissues and organs (ex: brain, heart, bones, among others), which constitutes a limiting factor in MRI as an adjuvant approach... In turn, some authors (Truong and Song, ; Roth and Basser, ; Wijesinghe and Roth, ; Roth et al., ) have argued to record, mainly the neural activity, based on Lorentz effect... The Lorentz effect relies on the idea of a conductor carrying a current exposed to a magnetic field can be submitted to a movement enough to cause a disturbance in the spin dynamics, which would result in an artifact in the MRI signal... Indeed, we may say yes... Many technological advances have been made and, as a result, different approaches have emerged as alternatives to other magnetometers such as SQUIDs in biomagnetic measurements... Therefore, we conclude that, MMG may become in the near future a promising and complementary approach to electrical and mechanical recordings in skeletal muscle physiology studies.

No MeSH data available.


Drawings of basic designs of (A) a toroidal pickup coil built for collecting MMG signals from biceps brachii muscle (adapted from Nantel and Pengelly, 1991; A: Amplifier system), (B) a SQUID (one channel) set-up mounted in an insulating vessel (adapted from Oschman, 2002). The measures given are approximate guides.
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Figure 1: Drawings of basic designs of (A) a toroidal pickup coil built for collecting MMG signals from biceps brachii muscle (adapted from Nantel and Pengelly, 1991; A: Amplifier system), (B) a SQUID (one channel) set-up mounted in an insulating vessel (adapted from Oschman, 2002). The measures given are approximate guides.

Mentions: The magnitude of the MMG signal is lower when compared to other biological tissues (heart, for example) and can range from pico (10−12) to femto (10−15) Tesla (T), depending on the approach of measurement. In this respect, the MMG signal can be collected by means of toroidal pickup coils and Superconducting Quantum Interference Devices (SQUIDs). Wound toroidal pickup coils can have different sizes of cores, wire gauges and number of turns (Williamson et al., 1983) (Figure 1A). As action potentials propagate along skeletal muscle fibers, the magnetic fields induced around them will induce a current in the toroid by Faraday's Law (Skoczelas, 2009). In turn, SQUIDs are characterized by an array of one or more coils immersed in liquid helium to maintain a superconductive state (Figure 1B). Although both magnetometers can be used in MMG signal acquisitions, SQUIDs allow detecting such low range of magnetic fields with a higher spatial resolution in comparison to wound toroidal pickup coils and have been preferably adopted by most of authors whenever possible.


Magnetic fields from skeletal muscles: a valuable physiological measurement?

Garcia MA, Baffa O - Front Physiol (2015)

Drawings of basic designs of (A) a toroidal pickup coil built for collecting MMG signals from biceps brachii muscle (adapted from Nantel and Pengelly, 1991; A: Amplifier system), (B) a SQUID (one channel) set-up mounted in an insulating vessel (adapted from Oschman, 2002). The measures given are approximate guides.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4530668&req=5

Figure 1: Drawings of basic designs of (A) a toroidal pickup coil built for collecting MMG signals from biceps brachii muscle (adapted from Nantel and Pengelly, 1991; A: Amplifier system), (B) a SQUID (one channel) set-up mounted in an insulating vessel (adapted from Oschman, 2002). The measures given are approximate guides.
Mentions: The magnitude of the MMG signal is lower when compared to other biological tissues (heart, for example) and can range from pico (10−12) to femto (10−15) Tesla (T), depending on the approach of measurement. In this respect, the MMG signal can be collected by means of toroidal pickup coils and Superconducting Quantum Interference Devices (SQUIDs). Wound toroidal pickup coils can have different sizes of cores, wire gauges and number of turns (Williamson et al., 1983) (Figure 1A). As action potentials propagate along skeletal muscle fibers, the magnetic fields induced around them will induce a current in the toroid by Faraday's Law (Skoczelas, 2009). In turn, SQUIDs are characterized by an array of one or more coils immersed in liquid helium to maintain a superconductive state (Figure 1B). Although both magnetometers can be used in MMG signal acquisitions, SQUIDs allow detecting such low range of magnetic fields with a higher spatial resolution in comparison to wound toroidal pickup coils and have been preferably adopted by most of authors whenever possible.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biociências da Atividade Física, Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brasil ; Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo Ribeirão Preto, Brasil.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

It is well known that whenever a motor unit is recruited, electrical, and mechanical events are generated in skeletal muscle fibers... In addition, when skeletal muscle fibers are injured, there is a leakage of current that can be easily detected by SQUIDs, which also help to better map sites of muscle lesions (Curio et al., ; Mackert et al., )... Another important issue is that the MMG signal amplitude seems to be linearly correlated with muscle force production (Rutten et al., ; Gielen et al., ) in contrast to the EMG signal that is still under discussion (Hashemi et al., )... It can be especially useful in the simplification of mathematical models with added reliability in predicting muscle force production from the MMG signal instead the EMG... Furthermore, as a superconductor device, SQUIDs require to be cooled with liquid helium, which is operationally difficult to handle and very expensive, limiting a wide use of this approach... Alternatively, few authors have also attempted to detect magnetic fields of neural and skeletal muscle fibers using magnetic resonance imaging (MRI) although they did not succeed yet (Wijesinghe and Roth, ; Roth et al., )... The skeletal muscles present a magnetic susceptibility lower when compared to other biological tissues and organs (ex: brain, heart, bones, among others), which constitutes a limiting factor in MRI as an adjuvant approach... In turn, some authors (Truong and Song, ; Roth and Basser, ; Wijesinghe and Roth, ; Roth et al., ) have argued to record, mainly the neural activity, based on Lorentz effect... The Lorentz effect relies on the idea of a conductor carrying a current exposed to a magnetic field can be submitted to a movement enough to cause a disturbance in the spin dynamics, which would result in an artifact in the MRI signal... Indeed, we may say yes... Many technological advances have been made and, as a result, different approaches have emerged as alternatives to other magnetometers such as SQUIDs in biomagnetic measurements... Therefore, we conclude that, MMG may become in the near future a promising and complementary approach to electrical and mechanical recordings in skeletal muscle physiology studies.

No MeSH data available.