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. 2013 May 23:2013:505840.
doi: 10.1155/2013/505840. Print 2013.

Design methodology of a new wavelet basis function for fetal phonocardiographic signals

Vijay S Chourasia  1 , Anil Kumar Tiwari
Affiliations

Design methodology of a new wavelet basis function for fetal phonocardiographic signals

Vijay S Chourasia et al. ScientificWorldJournal. .

Abstract

Fetal phonocardiography (fPCG) based antenatal care system is economical and has a potential to use for long-term monitoring due to noninvasive nature of the system. The main limitation of this technique is that noise gets superimposed on the useful signal during its acquisition and transmission. Conventional filtering may result into loss of valuable diagnostic information from these signals. This calls for a robust, versatile, and adaptable denoising method applicable in different operative circumstances. In this work, a novel algorithm based on wavelet transform has been developed for denoising of fPCG signals. Successful implementation of wavelet theory in denoising is heavily dependent on selection of suitable wavelet basis function. This work introduces a new mother wavelet basis function for denoising of fPCG signals. The performance of newly developed wavelet is found to be better when compared with the existing wavelets. For this purpose, a two-channel filter bank, based on characteristics of fPCG signal, is designed. The resultant denoised fPCG signals retain the important diagnostic information contained in the original fPCG signal.

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Figures

Figure 1
Figure 1
(a) Typical fPCG signal and (b) its frequency spectrum.
Figure 2
Figure 2
Wavelet thresholding.
Figure 3
Figure 3
Waveform of (a) reference fPCG signal and (b) test fPCG signal with additive noise.
Figure 4
Figure 4
Denoised fPCG signal using different algorithms: (a) sqtwolog(s), (b) sqtwolog(h), (c) minimaxi(s), (d) minimaxi(h), (e) rigrsure(s), and (f) rigrsure(h).
Figure 5
Figure 5
Two-channel filter bank.
Figure 6
Figure 6
Impulse response for the reconstruction and decomposition filters of fetal.
Figure 7
Figure 7
Wavelet and scaling function of “fetal” wavelet.
Figure 8
Figure 8
Simulink model for wavelet denoising.
Figure 9
Figure 9
Waveforms of a real fPCG signal and its denoised version.
See this image and copyright information in PMC

References

    1. Chourasia VS, Tiwari AK. A review and comparative analysis of recent advancements in fetal monitoring techniques. Critical Reviews in Biomedical Engineering. 2008;36(5-6):335–373. - PubMed
    1. Murray M. Antepartal and Intrapartal Fetal Monitoring. 3rd edition. Springer; 2007.
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    1. Kovács F, Török M, Habermajer I. A rule-based phonocardiographic method for long-term fetal heart rate monitoring. IEEE Transactions on Biomedical Engineering. 2000;47(1):124–130. - PubMed
    1. Jianfeng C, Phua K, Ying S, Shue L. A portable phonocardiographic fetal heart rate monitor. Proceedings of the IEEE International Symposium on Circuits and Systems; May 2006; Island of Kos, Greece. pp. 2141–2144.

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