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      Is Open Access
      Frontiers in Neuroscience
      Frontiers Media S.A.
      motion artifact, nirs, functional near-infrared spectroscopy, near-infrared spectroscopy, hemodynamic response

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          Abstract

          Near-infrared spectroscopy (NIRS) is susceptible to signal artifacts caused by relative motion between NIRS optical fibers and the scalp. These artifacts can be very damaging to the utility of functional NIRS, particularly in challenging subject groups where motion can be unavoidable. A number of approaches to the removal of motion artifacts from NIRS data have been suggested. In this paper we systematically compare the utility of a variety of published NIRS motion correction techniques using a simulated functional activation signal added to 20 real NIRS datasets which contain motion artifacts. Principle component analysis, spline interpolation, wavelet analysis, and Kalman filtering approaches are compared to one another and to standard approaches using the accuracy of the recovered, simulated hemodynamic response function (HRF). Each of the four motion correction techniques we tested yields a significant reduction in the mean-squared error (MSE) and significant increase in the contrast-to-noise ratio (CNR) of the recovered HRF when compared to no correction and compared to a process of rejecting motion-contaminated trials. Spline interpolation produces the largest average reduction in MSE (55%) while wavelet analysis produces the highest average increase in CNR (39%). On the basis of this analysis, we recommend the routine application of motion correction techniques (particularly spline interpolation or wavelet analysis) to minimize the impact of motion artifacts on functional NIRS data.

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          Most cited references19

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          HomER: a review of time-series analysis methods for near-infrared spectroscopy of the brain.

          Near-infrared spectroscopy (NIRS) is a noninvasive neuroimaging tool for studying evoked hemodynamic changes within the brain. By this technique, changes in the optical absorption of light are recorded over time and are used to estimate the functionally evoked changes in cerebral oxyhemoglobin and deoxyhemoglobin concentrations that result from local cerebral vascular and oxygen metabolic effects during brain activity. Over the past three decades this technology has continued to grow, and today NIRS studies have found many niche applications in the fields of psychology, physiology, and cerebral pathology. The growing popularity of this technique is in part associated with a lower cost and increased portability of NIRS equipment when compared with other imaging modalities, such as functional magnetic resonance imaging and positron emission tomography. With this increasing number of applications, new techniques for the processing, analysis, and interpretation of NIRS data are continually being developed. We review some of the time-series and functional analysis techniques that are currently used in NIRS studies, we describe the practical implementation of various signal processing techniques for removing physiological, instrumental, and motion-artifact noise from optical data, and we discuss the unique aspects of NIRS analysis in comparison with other brain imaging modalities. These methods are described within the context of the MATLAB-based graphical user interface program, HomER, which we have developed and distributed to facilitate the processing of optical functional brain data.
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            Functional near infrared spectroscopy (NIRS) signal improvement based on negative correlation between oxygenated and deoxygenated hemoglobin dynamics.

            Near infrared spectroscopy (NIRS) is a promising technology for functional brain imaging which measures hemodynamic signals from the cortex, similar to functional magnetic resonance imaging (fMRI), but does not require the participant to lie motionless in a confined space. NIRS can therefore be used for more naturalistic experiments, including face to face communication, or natural body movements, and is well suited for real-time applications that may require lengthy training. However, improving signal quality and reducing noise, especially noise induced by head motion, is challenging, particularly for real time applications. Here we study the properties of head motion induced noise, and find that motion noise causes the measured oxygenated and deoxygenated hemoglobin signals, which are typically strongly negatively correlated, to become more positively correlated. Next, we develop a method to reduce noise based on the principle that the concentration changes of oxygenated and deoxygenated hemoglobin should be negatively correlated. We show that despite its simplicity, this method is effective in reducing noise and improving signal quality, for both online and offline noise reduction. Copyright 2009 Elsevier Inc. All rights reserved.
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              How to detect and reduce movement artifacts in near-infrared imaging using moving standard deviation and spline interpolation.

              Near-infrared imaging (NIRI) is a neuroimaging technique which enables us to non-invasively measure hemodynamic changes in the human brain. Since the technique is very sensitive, the movement of a subject can cause movement artifacts (MAs), which affect the signal quality and results to a high degree. No general method is yet available to reduce these MAs effectively. The aim was to develop a new MA reduction method. A method based on moving standard deviation and spline interpolation was developed. It enables the semi-automatic detection and reduction of MAs in the data. It was validated using simulated and real NIRI signals. The results show that a significant reduction of MAs and an increase in signal quality are achieved. The effectiveness and usability of the method is demonstrated by the improved detection of evoked hemodynamic responses. The present method can not only be used in the postprocessing of NIRI signals but also for other kinds of data containing artifacts, for example ECG or EEG signals.
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                Author and article information

                Journal
                Front Neurosci
                Front. Neurosci.
                Frontiers in Neuroscience
                Frontiers Media S.A.
                1662-4548
                1662-453X
                11 October 2012
                2012
                : 6
                : 147
                Affiliations
                [1] 1Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School Charlestown, MA, USA
                [2] 2Harvard-MIT Division of Health Sciences and Technology Cambridge, MA, USA
                [3] 3Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology Cambridge, MA, USA
                [4] 4Danish Headache Center, Department of Neurology, Glostrup Hospital, Faculty of Health Sciences, University of Copenhagen Copenhagen, Denmark
                [5] 5Stroke Unit, Department of Neurology, Glostrup Hospital, Faculty of Health Sciences, University of Copenhagen Copenhagen, Denmark
                Author notes

                Edited by: Jessica A. Turner, Mind Research Network, USA

                Reviewed by: Joshua Vogelstein, Johns Hopkins, USA; Felix Scholkmann, Biomedical Optics Research Laboratory, Switzerland

                *Correspondence: David A. Boas, Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Room 2301, 149, 13th Street, Charlestown, MA 02129, USA. e-mail: dboas@ 123456nmr.mgh.harvard.edu

                This article was submitted to Frontiers in Brain Imaging Methods, a specialty of Frontiers in Neuroscience.

                Article
                10.3389/fnins.2012.00147
                3468891
                23087603
                e2ddb198-7d11-4d38-9054-67f98c939f42
                Copyright © 2012 Cooper, Selb, Gagnon, Phillip, Schytz, Iversen, Ashina and Boas.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.

                History
                : 25 July 2012
                : 17 September 2012
                Page count
                Figures: 6, Tables: 0, Equations: 6, References: 25, Pages: 10, Words: 7950
                Categories
                Neuroscience
                Original Research

                Neurosciences
                motion artifact,nirs,functional near-infrared spectroscopy,near-infrared spectroscopy,hemodynamic response

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