title: Iterative Covariance-Based Removal of Time-Synchronous Artifacts: Application to Gastrointestinal Electrical Recordings.
abstract: The aim of this study was to develop, validate, and apply a fully automated method for reducing large temporally synchronous artifacts present in electrical recordings made from the gastrointestinal (GI) serosa, which are problematic for properly assessing slow wave dynamics. Such artifacts routinely arise in experimental and clinical settings from motion, switching behavior of medical instruments, or electrode array manipulation.
  
  
  
  A novel iterative Covariance-Based Reduction of Artifacts (COBRA) algorithm sequentially reduced artifact waveforms using an updating across-channel median as a noise template, scaled and subtracted from each channel based on their covariance.
  
  
  
  Application of COBRA substantially increased the signal-to-artifact ratio (12.8 ± 2.5 dB), while minimally attenuating the energy of the underlying source signal by 7.9% on average ( -11.1 ± 3.9 dB).
  
  
  
  COBRA was shown to be highly effective for aiding recovery and accurate marking of slow wave events (sensitivity = 0.90 ± 0.04; positive-predictive value = 0.74 ± 0.08) from large segments of in vivo porcine GI electrical mapping data that would otherwise be lost due to a broad range of contaminating artifact waveforms.
  
  
  
  Strongly reducing artifacts with COBRA ultimately allowed for rapid production of accurate isochronal activation maps detailing the dynamics of slow wave propagation in the porcine intestine. Such mapping studies can help characterize differences between normal and dysrhythmic events, which have been associated with GI abnormalities, such as intestinal ischemia and gastroparesis. The COBRA method may be generally applicable for removing temporally synchronous artifacts in other biosignal processing domains.
authors.affiliation: Department of Physics and Engineering, Washington and Lee University, Lexington, VA, USA.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Erickson
authors.affiliation: Department of Physics and Engineering, Washington and Lee University.
authors.forename: Joy
authors.initials: J
authors.lastname: Putney
authors.affiliation: Departments of Mathematics and Biochemistry, Washington and Lee University.
authors.forename: Douglas
authors.initials: D
authors.lastname: Hilbert
authors.affiliation: Auckland Bioengineering InstituteUniversity of Auckland.
authors.forename: Niranchan
authors.initials: N
authors.lastname: Paskaranandavadivel
authors.affiliation: Auckland Bioengineering Institute.
authors.forename: Leo K
authors.initials: LK
authors.lastname: Cheng
authors.affiliation: Auckland Bioengineering Institute.
authors.forename: Greg
authors.initials: G
authors.lastname: O'Grady
authors.affiliation: Auckland Bioengineering InstituteUniversity of Auckland.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Angeli
mesh_terms: D000465:Algorithms; D000818:Animals; D016477:Artifacts; D016208:Databases, Factual; D004594:Electrophysiology / Q000379:methods*; D007583:Jejunum / Q000502:physiology*; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013552:Swine
references.citation: J Physiol. 2013 Sep 15;591(18):4567-79
references.pmid: 23713030
references.citation: IEEE Trans Biomed Eng. 2000 Oct;47(10):1406-11
references.pmid: 11059176
references.citation: Am J Surg. 1978 Aug;136(2):242-6
references.pmid: 686270
references.citation: Neural Comput. 2004 Aug;16(8):1661-87
references.pmid: 15228749
references.citation: Med Biol Eng Comput. 2000 Jan;38(1):35-41
references.pmid: 10829388
references.citation: IEEE Trans Biomed Eng. 2005 Jan;52(1):74-87
references.pmid: 15651566
references.citation: Can J Surg. 1976 Jul;19(4):316-21
references.pmid: 949644
references.citation: J Neurogastroenterol Motil. 2013 Apr;19(2):179-91
references.pmid: 23667749
references.citation: J Neural Eng. 2015 Jun;12(3):031001
references.pmid: 25834104
references.citation: Ann Biomed Eng. 2014 Jan;42(1):177-92
references.pmid: 24048711
references.citation: Neurogastroenterol Motil. 2013 Jan;25(1):79-83
references.pmid: 22974243
references.citation: Ann Biomed Eng. 2013 Oct;41(10 ):2215-28
references.pmid: 23612912
references.citation: Neurogastroenterol Motil. 2013 May;25(5):353-7
references.pmid: 23490042
references.citation: Clin Neurophysiol. 2007 Jan;118(1):98-104
references.pmid: 17088100
references.citation: Ann Biomed Eng. 2011 Jan;39(1):469-83
references.pmid: 20927594
references.citation: Reprod Sci. 2013 Feb;20(2):182-9
references.pmid: 22649122
references.citation: Ann Biomed Eng. 2010 Jul;38(7):2358-70
references.pmid: 20232149
references.citation: Am J Physiol Gastrointest Liver Physiol. 2010 Sep;299(3):G585-92
references.pmid: 20595620
references.citation: IEEE Trans Biomed Eng. 2015 Nov;62(11):2553-67
references.pmid: 26415149
references.citation: Physiol Meas. 2008 Dec;29(12):1351-69
references.pmid: 18946157
references.citation: Ann Biomed Eng. 2010 Apr;38(4):1511-29
references.pmid: 20024624
references.citation: IEEE Trans Neural Syst Rehabil Eng. 2013 May;21(3):427-34
references.pmid: 23673459
references.citation: Acta Physiol (Oxf). 2015 Feb;213(2):406-16
references.pmid: 25393600
references.citation: Neurogastroenterol Motil. 2013 May;25(5):e304-14
references.pmid: 23489929
references.citation: Neurogastroenterol Motil. 2012 Jan;24(1):1-6
references.pmid: 22188324
references.citation: Conf Proc IEEE Eng Med Biol Soc. 2011;2011:1737-40
references.pmid: 22254662
references.citation: Psychophysiology. 2004 Mar;41(2):313-25
references.pmid: 15032997
references.citation: Gastroenterology. 2008 Nov;135(5):1601-11
references.pmid: 18713627
references.citation: Ann Biomed Eng. 2009 Apr;37(4):839-46
references.pmid: 19224368
references.citation: Am J Physiol Gastrointest Liver Physiol. 2009 Jun;296(6):G1200-10
references.pmid: 19359425
references.citation: Neurogastroenterol Motil. 2011 Sep;23(9):815-8
references.pmid: 21838727
references.citation: Wiley Interdiscip Rev Syst Biol Med. 2010 Jan-Feb;2(1):65-79
references.pmid: 20836011
references.citation: J Neurosci Methods. 2002 Oct 30;120(2):113-20
references.pmid: 12385761
references.citation: IEEE Trans Biomed Eng. 2013 Oct;60(10):2760-70
references.pmid: 23708770
references.citation: Gastroenterology. 2012 Sep;143(3):589-98.e1-3
references.pmid: 22643349
references.citation: Clin Exp Pharmacol Physiol. 2014 Oct;41(10):854-62
references.pmid: 25115692
references.citation: IEEE Trans Biomed Eng. 2014 Nov;61(11):2679-87
references.pmid: 24860024
references.citation: IEEE Trans Inf Technol Biomed. 2012 May;16(3):488-500
references.pmid: 22361665
references.citation: Neurogastroenterol Motil. 2002 Aug;14(4):357-64
references.pmid: 12213103
references.citation: Neurogastroenterol Motil. 2010 Oct;22(10):e292-300
references.pmid: 20618830
references.citation: Can J Physiol Pharmacol. 2005 Nov;83(11):1031-43
references.pmid: 16391712
references.citation: IEEE Trans Biomed Eng. 2002 Jul;49(7):681-8
references.pmid: 12083302
references.citation: BMC Gastroenterol. 2012 Jun 06;12:60
references.pmid: 22672254
references.citation: Med Biol Eng Comput. 2008 Feb;46(2):121-9
references.pmid: 18200451