title: Suppression of stimulus artifact contaminating electrically evoked electromyography.
abstract: BACKGROUND
  Electrical stimulation of muscle or nerve is a very useful technique for understanding of muscle activity and its pathological changes for both diagnostic and therapeutic purposes. During electrical stimulation of a muscle, the recorded M wave is often contaminated by a stimulus artifact. The stimulus artifact must be removed for appropriate analysis and interpretation of M waves.
  
  
  OBJECTIVE
  The objective of this study was to develop a novel software based method to remove stimulus artifacts contaminating or superimposing with electrically evoked surface electromyography (EMG) or M wave signals.
  
  
  METHODS
  The multiple stage method uses a series of signal processing techniques, including highlighting and detection of stimulus artifacts using Savitzky-Golay filtering, estimation of the artifact contaminated region with Otsu thresholding, and reconstruction of such region using signal interpolation and smoothing. The developed method was tested using M wave signals recorded from biceps brachii muscles by a linear surface electrode array. To evaluate the performance, a series of semi-synthetic signals were constructed from clean M wave and stimulus artifact recordings with different degrees of overlap between them.
  
  
  RESULTS
  The effectiveness of the developed method was quantified by a significant increase in correlation coefficient and a significant decrease in root mean square error between the clean M wave and the reconstructed M wave, compared with those between the clean M wave and the originally contaminated signal. The validity of the developed method was also demonstrated when tested on each channel's M wave recording using a linear electrode array.
  
  
  CONCLUSIONS
  The developed method can suppress stimulus artifacts contaminating M wave recordings.
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center at Houston, Houston, TX, USA The Neurorehabilitation Research Laboratory, The Institute of Rehabilitation and Research (TIRR)-Memorial Hermann Hospital, Houston, TX, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Li
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Li
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA.
authors.forename: Cliff
authors.initials: C
authors.lastname: Klein
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, USA.
authors.forename: William Z
authors.initials: WZ
authors.lastname: Rymer
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, USA Institute of Biomedical Engineering, University of Science and Technology of China, Hefei, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhou
mesh_terms: D001132:Arm; D016477:Artifacts; D004558:Electric Stimulation / Q000379:methods*; D004576:Electromyography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D012984:Software
keywords: M wave; electromyography (EMG); stimulus artifact suppression