Time-frequency analysis of foetal heart sound signal for the prediction of prenatal anomalies

Abstract

Motion of the foetal heart gives rise to vibrations and sounds that can be acquired through the surface of the maternal abdominal wall. The process is called foetal phonocardiography (fPCG) and its study has shown to be a very useful mechanism to evaluate the wellbeing of the unborn. These signals exhibit innate rhythms and periodicity that are more readily expressed and appreciated in terms of frequency than time units. Time-frequency distribution shows the spectral composition of signal at a particular time instant, which is also known as a spectrogram. This work investigates the analysis of foetal heart sound using time frequency distribution generated by short-time Fourier transform (STFT). An innovative method is presented for foetal heart sound acquisition, processing and coloured spectral representation, which can be used in a portable foetal home monitoring system. The outcome of the work is a numerous spectral display produced by the system for varied real and simulated foetal heart sound signals. A comparative study of normal and abnormal heart sound is presented. The spectrograms exhibit noticeable morphological differences in terms of duration and spectral composition of the sounds. The study suggests that STFT based coloured spectrograms can become an important diagnostic tool, and it is expected that the presented work will facilitate the potential use of the method in prediction of the prenatal anomalies.

A Review of Recent Advances and Future Developments in Fetal Phonocardiography

“…For this reason, methods for automatic identification of the individual fHSs have been presented in the past. They were mainly based on the thresholding and conditioning according to the physiological properties of the heart cycle [16], [17], but also other alternatives proved to be effective, such as those using spectrogram [18] or a combination of scalogram and physiological properties of fPCG [19].…”

A comparative study of single-channel signal processing methods in fetal phonocardiography

“…In particular, the evaluation of the accuracy of S2 detection is not very common in the field of fPCG (except for very few publications, e.g. [16][17][18]), although this information is useful for clinical practice. The benefit of the study is also to test the performance of algorithms in many scenarios, such as different types and levels of interference.…”

“…In particular, the evaluation of the accuracy of S2 detection, which is a clinically valuable feature, is quite rare except for very few studies focus on this topic, e.g. [16][17][18].…”

Fetal heart rate estimation from a single phonocardiogram signal using non-negative matrix factorization

“…Adaptive filtering technique [12] is also proposed but it suffers from a lack of robustness. In lineardecomposition group, one can cite methods based on timefrequency representation like short-time Fourier transform (STFT) [13], wavelets transform [14], which are efficient in signal analysis, and blind source separation (BSS) [15]. In addition, most of the existent PCG-based methods, as in [16], [17], need to locate and differentiate on the PCG signal envelop, the instants of S 1 and S 2 sounds, which are the most audible cardiac sounds and correspond to the closure of respectively the atrial-ventricular, and the aortic and pulmonary valves.…”