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. Objectives 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 the Savitzky-Golay filtering, estimation of the artifact contaminated region with the 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 the linear electrode array. Conclusions The developed method can suppress stimulus artifacts contaminating M wave recordings.

Imaging three-dimensional innervation zone distribution in muscles from M-wave recordings

“…The stimulation artefacts were then identified and removed using a recently developed approach [42]. Muscle EMG responses recorded under different stimulation intensities were segmented.…”

Non‐invasive electromyographic estimation of motor unit number in the external anal sphincter of the rat

“…Stimulation artifacts were detected automatically using a Salvasky-Golay filter, and an Otsu thresholding protocol. 15 The amplitude of the first negative peak following the stimulation onset was extracted as the CMAP value for further MUNE calculation. Recorded data were excluded, if more than 50% of the CMAP responses fell out the pre-set CMAP window.…”

Avaliação de métodos adaptativos e baseados em software para compensação de artefato de estímulo em sEMG

“…Esse potencial eletricamente evocado captado através da eletromiografia de superfície (sEMG) usualmente é contaminado por um artefato, devido ao estímulo elétrico, que pode ser várias vezes maior que o sinal de interesse 2 . Devido ao artefato apresentar sincronização temporal e sobreposição espectral parcial com a onda M, a sua remoção por meio de técnicas como promediação ou filtragem simples 3 torna-se complicada.…”

“…Em virtude da soma do artefato à onda M, pode ocorrer alteração das estimativas da velocidade de condução, de características espectrais e da amplitude do sinal 5 . Além disso, dependendo do grau de sobreposição, o qual é dependente da distância entre o ponto de detecção e a zona de inervação, torna-se impossível a obtenção de boas medidas de latência da onda M adquirida 2 .…”