Abstract
Objective. To non-invasively determine muscle activity.
Design. A correlation analysis study.
Background. Electromyography is traditionally used to measure the electrical activity of a muscle
and can be used to estimate muscle contraction intensity. This approach, however,
is limited not only in terms of the volume of tissue that can be monitored, but must
be invasive if deep lying muscles are studied. We wished to avoid these limitations
and used magnetic resonance elastography in an attempt to non-invasively determine
muscle activity. This novel approach uses a conventional MRI system. However, in addition
to the imaging gradients, an oscillating, motion sensitizing field gradient is applied
to detect mechanical waves that have been generated within the tissue. The wavelength
correlates with the stiffness of the muscle and hence with the activity of the muscle.
Methods. Six volunteers (mean age: 30.1 years, range: 27–36 years) without orthopedic or neuromuscular
abnormalities, lay supine with their legs within the coil of a MRI scanner. The wavelengths
of mechanically generated shear waves in the tibialis anterior, medial and lateral
head of the gastrocnemius and the soleus were measured as the subjects resisted ankle
plantar-flexing (8.2 and 16.4 nm) and dorsi-flexing (20.2 and 40.4 nm) moments. The
findings were then compared to EMG data collected under the same loading conditions.
Results. Magnetic resonance elastography wavelengths were linearly correlated to the muscular
activity as defined by electromyography. (TA, R2=0.89, P=0.02; MG, R2=0.82, P=0.05; LG, R2=0.88, P=0.03; S, R2=0.90, P=0.02)
Conclusions. Magnetic resonance elastography may be a promising tool for the non-invasive determination
of muscle activity.
Relevance Magnetic resonance elastography has potential as the basis for a new non-invasive
approach to study in vivo muscle function.
Keywords
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Article info
Publication history
Accepted:
March 20,
2003
Received:
July 15,
2002
Identification
Copyright
Published by Elsevier Inc.
