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Study of properties of periodic fetal movements and of the corresponding ultrasonic Doppler signals

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Kałużyński K. , Kret T. , Sieńko J.

Biocybernetics and Biomedical Engineering

2007

tom Vol. 27, no. 4

3-16

Doppler signals collected on the abdomen of the pregnant woman were submitted to the discrete wavelet transform using the db 10 wavelet. The wavelet reconstruction products were submitted to the autocorrelation analysis. The processing, supported with the ultrasonographic scanning enabled identification of the fetal periodic activities. The fetal pseudo-breathing movement velocity always falls in the range of 5-10 mm/s (Doppler frequency range 12.5-25 Hz), velocities of cardiac structures - in the range of 20-75 mm/s (Doppler frequency 50-200 Hz). The signals resulting from fetal displacements provoked by maternal breathing and cardiac action or fetal hiccup are expected not to adversely affect estimation of the fetal rhythms. These findings are important for the development of fetal monitoring systems.

The fetal heart rate estimation based on continuous ultrasonic Doppler data

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Kret T. , Kałużyński K.

Biocybernetics and Biomedical Engineering

2006

tom Vol. 26, no. 3

49-56

Two methods to compute the fetal heart rate based on the analysis of Doppler signals obtained using continuous wave ultrasound were studied. The first uses bandpass filtering, directional signal separation and computation of the autocorrelation coefficient of the envelope of a single directional Doppler signal. The other uses discrete wavelet decomposition and reconstruction of a single directional signal with Daubechies db 10 wavelet family, with subsequent computation of the autocorrelation coefficient of the envelope of the reconstructed signal details for various scales. The results indicate that the discrete wavelet decomposition method is a suitable tool for fetal heart rate determination. It results in a more consistent fetal heart rate trace than the bandpass filtering approach.