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Published on: October 25, 2015
Removal of interference from fetal MEG by frequency dependent subtraction
J Vrba1, J McCubbin, R B Govindan
1Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. jvrba@shaw.ca
Abstract:
Fetal magnetoencephalography (fMEG) recordings are contaminated by maternal and fetal magnetocardiography (MCG) signals and by other biological and environmental interference. Currently, all methods for the attenuation of these signals are based on a time-domain approach. We have developed and tested a frequency dependent procedure for removal of MCG and other interference from the fMEG recordings. The method uses a set of reference channels and performs subtraction of interference in the frequency domain (SUBTR). The interference-free frequency domain signals are converted back to the time domain. We compare the performance of the frequency dependent approach with our present approach for MCG attenuation based on orthogonal projection (OP). SUBTR has an advantage over OP and similar template approaches because it removes not only the MCG but also other small amplitude biological interference, avoids the difficulties with inaccurate determination of the OP operator, provides more consistent and stable fMEG results, does not cause signal redistribution, and if references are selected judiciously, it does not reduce fMEG signal amplitude. SUBTR was found to perform well in simulations and on real fMEG recordings, and has a potential to improve the detection of fetal brain signals. The SUBTR removes interference without the need for a model of the individual interference sources. The method may be of interest for any sensor array noise reduction application where signal-free reference channels are available.
Insights
A new frequency-domain method (SUBTR) effectively removes maternal and fetal magnetocardiography (MCG) interference from fetal magnetoencephalography (fMEG) recordings. This approach enhances fetal brain signal detection by offering more stable and accurate results than current time-domain methods.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Signal Processing
Background:
- Fetal magnetoencephalography (fMEG) is crucial for assessing fetal brain development.
- fMEG signals are often obscured by maternal and fetal magnetocardiography (MCG) and other biological/environmental noise.
- Existing noise reduction techniques primarily use time-domain approaches, which have limitations.
Purpose of the Study:
- To develop and evaluate a novel frequency-dependent method for removing interference from fMEG recordings.
- To compare the efficacy of the new frequency-domain method against the current time-domain orthogonal projection (OP) approach for MCG attenuation.
Main Methods:
- Developed a frequency-dependent subtraction (SUBTR) method utilizing reference channels to remove interference in the frequency domain.
- Converted processed frequency-domain signals back to the time domain for analysis.
- Compared SUBTR performance against the orthogonal projection (OP) method using simulations and real fMEG data.
Main Results:
- The SUBTR method successfully removed MCG and other biological interference from fMEG recordings.
- SUBTR demonstrated advantages over OP, including handling of small amplitude noise and avoiding operator inaccuracies.
- SUBTR provided more consistent and stable fMEG results without signal redistribution or amplitude reduction.
Conclusions:
- The frequency-dependent SUBTR method offers a significant improvement for cleaning fMEG data.
- SUBTR has the potential to enhance the detection of fetal brain activity.
- This noise reduction technique may be applicable to other sensor array applications with available reference channels.
