View Full Version : MMG signals - summary

Adriano Andrade
11-13-2002, 01:18 AM
Dear All,

I am very thankful for receiving so many responses to my enquiry
regarding MMG signals. Special thanks are to Frank B, Joel T Cramer, Edmund
Cramp and Kyle Ebersole. A summary of the answers follows bellow:

“Indeed one can use microphones or small acclerometers to recording vmg etc.
Dytran has miniature acclerometers but they are quite expensive, and we have
not yet got good data w/ that (but others have?). VTI Hamlin has quite
affordable accelerometers (around $50 if I remember correctly). These are in
forms of chips (e.g. SCA 610 series) so one has to glue them onto small
plastic bended pieces in order to get them oriented in the right direction.
With inbuilt amplifier they are very simple to use. Small electret
microphones can also be used (around a couple of euro a piece) As an
experiment we plugged a microphone into an ordinary stethoscope (cut off
part of the "tube" and inserted the microphone into the tube). Preferable
one should make a somewhat lighter "cup" for collecting the sound (amplifies
the air pressure that reaches the microphone)”

“Different nomenclature has been used to describe the mechanomyographic
signal (i.e., acoustic myography, vibromyography, sound myography, and
mechanomyography). We have chosen to use the term mechanomyography (MMG) in
our studies to be consistent
with the suggestion of Orizio, C. (1993). Muscle sound: bases for the
introduction of mechanomyographic signal in muscle studies. Crit Rev Biomed
Eng, 21: 201-243. As you may already know, Dr. Orizio's review is a very
helpful source of information on a number of topics regarding MMG. Also,
the review by Stokes, M.J. (1993). Acoustic myography: applications and
considerations in measuring muscle performance. Isokin
Exer Sci, 3: 4-15 is another helpful source. I am not familiar with any
literature indicating that the nomenclature is a function of the type of
sensor used to record the signal. Dr. Claudio Orizio's review, however,
briefly discusses the different terminologies used and provides a
justification for the use of "mechanomyography."

There are two basic classifications of MMG signal acquisition units: 1.
piezoelectric crystal contact sensors, and 2. accelerometers. We use
Hewlett Packard (HP) 21050A piezoelectric crystal contact sensors in our
laboratory interfaced through a BIOPAC acquisition unit and A/D converter.
Again, sensor differences and justifications for using either are discussed
to great extent in Dr. Orizio's review. In addition, Dr. Watakabe has
published several recent papers on the use of different MMG sensors. The
following reference is the most recent publication of Watakabe et al. that I
am aware of on this topic. Further references are included in this paper.
Watakabe, M., Mita, K., Akataki, K., and Itoh, Y. (2001). Mechanical
behaviour of condensor microphone in mechanomyography. Medical &
Biological Engineering & Computing, 39: 195-201.”

“Since the EMG and AMG signal bandwidths are relatively similar, I would
expect that almost any modern EMG system could be used. I am certain our
own system (Motion Labs MA-300 - http://www.motion-labs.com/emg.htm)
would work”

“As for the recording device, most are either using an accelerometer OR a
heart sound/pulse contact sensor made by Philips Medical Systems. Little is
know on the potential differences between the devices, but the results tend
to be the same...or at least interpretation of the results. Dan Barry
published a paper on using the MMG signal as a prosthetic control (Arch Phy
Med Rehabil 67:267-269, 1986)”


Adriano de Oliveira Andrade , PhD student
University of Reading
Department of Cybernetics
Pepper Lane
Reading RG6 6AY, UK
tel: +44(0)118 378 7111
fax: +44(0)118 378 8220

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