Electrical Impedance Myography 

Differentiating muscle normality from abnormality.

Measures muscle composition and structure.

*Pending FDA clearance.

Building the clinical gold standard for measuring muscle health.*

Electrical impedance myography (EIM) is a non-invasive, breakthrough technique for the assessment of muscle condition that is based on the measurement of the electrical impedance characteristics of individual muscles or groups of muscles.

A muscle’s impedance can be used to measure whether a muscle is normal (healthy) or abnormal (likely injured or diseased) by assessing the overall muscle condition and structure. These factors are characteristic of abnormality:

    • Muscle fiber atrophy and disorganization
    • Presence of fat and connective tissue relative to amount of muscle fibers
    • Presence of inflammation
    • Muscle edema

*Pending FDA clearance.

Myolex EIM assesses the electrical filtering characteristics of muscle and is based upon the idea that a muscle’s conductivity and permittivity will become significantly altered by either injury or one of many kinds of neuromuscular or musculoskeletal disease. The integrity of individual cell membranes and alterations in the muscle’s structure and composition, including myocyte hypertrophy and atrophy, inflammation, edema, and connective tissue and fat deposition, will all significantly impact the measured impedances. 

Through numerous IRB-approved clinical trials, Myolex EIM has been used to discriminate between healthy and diseased muscle, and to assess tissue degradation and progressive muscle weakness over time.

How EIM Works

mScan® measures impedance characteristics across multiple frequencies relative to the major muscle fiber direction.



Current (blue) and voltage (yellow) electrodes are placed on a specific location over a muscle. A weak electrical current is passed through the tissue across a wide range of frequencies through the current electrodes.


Alterations in the health of the muscle are reflected in the measured voltages.


The Three Measures of EIM


Measures major resistance to the current through intra- and extracellular ionic fluids. Simple muscle atrophy will increase resistance of the tissue. Inflammation will cause edema in the muscle and reduce resistance. 


Highly related to myofiber membrane integrity and enables assessment of muscle fiber health. Reactance measures the additional muscle resistance due to capacitive elements such as cell membranes, tissue interfaces, and non-ionic substances. Progressive muscle atrophy yields markedly different reactance, which varies depending upon the frequency of the applied current.  


For a given resistance and reactance, phase angle can then be calculated. Phase angle represents the time-shift that a sinusoid undergoes when passing through the muscle. It is less impacted by muscle size or shape. 

App Data Display

Once scanning is completed, resistance, reactance, and phase measures can be plotted as a function of frequency to demonstrate the differences in frequency dependence between healthy and degrading muscle groups.

A highly sensitive, reproducible, more comprehensive measure of muscle composition and structure.    

All three parameters (resistance, reactance, and phase value) are measured across a range of frequencies (spectral analysis) and at multiple angles relative to the major muscle fiber direction. Different tissues (muscle, fat, bone, etc.) are sensitive to the frequencies in unique ways. Some tissues have a great effect on the electrical current at one frequency, but not at another. 

This is an important feature since it allows clinical researchers to separate the effects of fat from those of muscle, and it is a key reason underlying Myolex’s breakthrough innovation as a more sensitive and comprehensive muscle condition assessment.

This is particularly true for ALS.

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Brookline, MA 02446

Phone: 888.382.8824 

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