Adaptive spatial filtering of multichannel surface electromyogram signals |
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Authors: | Email author" target="_blank">N??stlundEmail author J?Yu K?Roeleveld J?S?Karlsson |
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Institution: | 1.Department of Biomedical Engineering & Informatics,University Hospital,Ume?,Sweden;2.Department of Rehabilitation Medicine,Faculty of Health Sciences,Link?ping,Sweden;3.Centre for Biomedical Engineering & Physics,Ume? University,Ume?,Sweden;4.Centre of Biostochastics,Swedish University of Agricultural Sciences,Ume?,Sweden;5.Human Movement Sciences Programme,Norwegian University of Science & Technology,Trondheim,Norway |
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Abstract: | Spatial filtering of surface electromyography (EMG) signal can be used to enhance single motor unit action potentials (MUAPs).
Traditional spatial filters for surface EMG do not take into consideration that some electrodes could have poor skin contact.
In contrast to the traditional a priori defined filters, this study introduces an adaptive spatial filtering method that adapts
to the signal characteristics. The adaptive filter, the maximum kurtosis filter (MKF), was obtained by using the linear combination
of surrounding channels that maximises kurtosis. The MKF and conventional filters were applied to simulated EMG signals and
to real EMG signals recorded with an electrode grid to evaluate their performance in detecting single motor units. The MKF
was compared with conventional spatial filtering methods. Simulated signals, with different levels of spatially correlated
noise, were used for comparison. The influence of one electrode with poor skin contact was also investigated. The MKF was
found to be considerably better at enhancing a single MUAP than conventional methods for all levels of spatial correlation
of the noise. For a spatial correlation of 0.97 of the noise, the improvement in the signal-to-noise ratio, where a MUAP could
be detected, was at least 6 dB. With a simulated poor skin contact for one electrode, the improvement over the other methods
was at least 19 dB. |
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Keywords: | Electromyography EMG Multichannel Spatial filter Kurtosis |
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