Quality control and artifact processing of electroencephalographic recordings



The quality of EEG recordings is limited by

The impedance noise is determined by U=(4.k.T.Z.B)1/2 with the Boltzmann constant k=1.3807e-23 J/K, the absolute temperature T  [K], the impedance Z [Ohm] and the bandwidth B [Hz]. The amplifier noise is determined mostly by the first amplifier (preamp) and its transistors. This is determined by the acquisition system. The quantization noise is also determined by the acquisition system, but might change with different gain settings.The Importance of these factors is demonstrated in the following example. The noise spectrum of  four different EEG amplifiers is shown. The dark black line indicates the quantization noise, the dashed line is the impedance noise of 4.7kOhm. The noise level differ by a factor of 2 even in the passband. The amplifier offset, amplifier noise, quantization noise, and entropy can be also quantified (see MW, GM, GT, NH)

Software tools for quality control and artifact processing are available from BioSig for Octave and Matlab.
If you are interested in evaluating your acquisition system, click here.

A. Schlögl, A. Ziehe, K.-R. Müller (2009)
Automated ocular artifact removal: comparing regression and component-based methods
Nature Precedings PrePrint
A. Schlögl, C. Keinrath, D. Zimmermann, R. Scherer, R. Leeb, G. Pfurtscheller.
A fully automated correction method of EOG artifacts in EEG recordings.
Clin. Neurophysiol. 2007 Jan;118(1):98-104. Epub 2006 Nov 7
ScienceDirect Paper(pdf)
A. Schlögl, B. Kemp, T. Penzel, D. Kunz, S.-L. Himanen, A. Värri, G. Dorffner, G. Pfurtscheller.
Quality Control of polysomnographic Sleep Data by Histogram and Entropy Analysis.
Clin. Neurophysiol. 1999, Dec; 110(12): 2165 - 2170.
ScienceDirect PDF Paper(pdf)
A. Schlögl, G. Klösch, W. Koele, J. Zeitlhofer, P.Rappelsberger, G. Pfurtscheller
Qualitätskontrolle von Biosignalen,
Jahrestagung der Österreichischen Gesellschaft für KlinischeNeurophysiologie, 27. Nov. 1999, Vienna.
Abstract: ps(deutsch)- - ps(english)
Presentation: /~schloegl/lectures/Q/index.htm
Penzel T, Kemp B, Klösch G, Schlögl A, Hasan J, Varri A, Korhonen I.
Acquisition of biomedical signals databases
IEEE Engineering in Medicine and Biology Magazine 2001, 20(3): 25-32
[Abstract]    [PDF Full-Text] 
A. Schlögl
Evaluating biomedical data acquisition systems.
Technical Report, 2002.[PDF Full-Text] 

Anderer P, Roberts SJ, Schlögl A, Gruber G, Klosch G, Herrmann W, Rappelsberger P, Filz O, Barbanoj MJ, Dorffner G, Saletu B.
Artifact Processing in Computerized Analysis of Sleep EEG - A Review.
Neuropsychobiology. 1999 Sep;40(3):150-157.
A. Schlögl, P. Anderer, M.-J. Barbanoj, G. Klösch, G. Gruber, J.L. Lorenzo, O. Filz, M. Koivuluoma, I. Rezek, S.J. Roberts, A. Värri, P. Rappelsberger, G. Pfurtscheller, G. Dorffner
Artifact processing of the sleep EEG in the "SIESTA"-project,
Proceedings EMBEC'99, Part II, pp.1644-1645, 4-7. Nov. 1999, Vienna, Austria.
ps(146kB) - - ps.gz(43kB)
A. Schlögl, P. Anderer, S.J. Roberts, M. Pregenzer, G. Pfurtscheller.
Artefact detection in sleep EEG by the use of Kalman filtering.
Proceedings EMBEC'99, Part II, pp.1648-1649, 4-7. Nov. 1999, Vienna, Austria.
ps (182kB) - - ps.gz(58kB)
K. C. Harke, A. Schlögl, P. Anderer, G. Pfurtscheller (1999)
Cardiac field artifact in sleep EEG,
Proceedings EMBEC'99, Part I, pp.482-483, 4-7. Nov. 1999, Vienna, Austria.
ps(210kB) - - ps.gz(80kB)
S.J. Roberts, R. Everson, I. Rezek, P. Anderer, A. Schlögl,
Tracking ICA for EEG Eye Movement Artifact Removal,
Proceedings EMBEC'99, Part II, pp.1646-1647, 4-7. Nov. 1999, Vienna, Austria.
A. Schlögl, P. Anderer, M.-J. Barbanoj, G. Dorffner,  G. Gruber, G. Klösch, J.L. Lorenzo, P. Rappelsberger, G. Pfurtscheller.
Artifacts in the sleep EEG - A database for the evaluation of automated processing methods.
Sleep Research Online 1999;2 (Supplement 1) p.586.
3rd Int. Congress of WFSRS, 5-8 Oct. 1999, Dresden. * * Proceeding (zipped postscript 48k) * * Poster (zipped postscript 48k) * *
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