An Improved FastICA Method for Fetal ECG Extraction.

Shuicai Wu,Zhuhuang Zhou,Li Yuan,Yanchao Yuan

doi:10.1155/2018/7061456

Shuicai Wu, Zhuhuang Zhou + Show 2 more

Open Access

https://doi.org/10.1155/2018/7061456

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Abstract

Objective The fast fixed-point algorithm for independent component analysis (FastICA) has been widely used in fetal electrocardiogram (ECG) extraction. However, the FastICA algorithm is sensitive to the initial weight vector, which affects the convergence of the algorithm. In order to solve this problem, an improved FastICA method was proposed to extract fetal ECG. Methods First, the maternal abdominal mixed signal was centralized and whitened, and the overrelaxation factor was incorporated into Newton's iterative algorithm to process the initial weight vector randomly generated. The improved FastICA algorithm was used to separate the source components, selected the best maternal ECG from the separated source components, and detected the R-wave location of the maternal ECG. Finally, the maternal ECG component in each channel was removed by the singular value decomposition (SVD) method to obtain a clean fetal ECG signal. Results An annotated clinical fetal ECG database was used to evaluate the improved algorithm and the conventional FastICA algorithm. The average number of iterations of the algorithm was reduced from 35 before the improvement to 13. Correspondingly, the average running time was reduced from 1.25 s to 1.04 s when using the improved algorithm. The signal-to-noise ratio (SNR) based on eigenvalues of the improved algorithm was 1.55, as compared to 0.99 of the conventional FastICA algorithm. The SNR based on cross-correlation coefficients of the conventional algorithm was also improved from 0.59 to 2.02. The sensitivity, positive predictive accuracy, and harmonic mean (F1) of the improved method were 99.37%, 99.00%, and 99.19%, respectively, while these metrics of the conventional FastICA method were 99.03%, 98.53%, and 98.78%, respectively. Conclusions The proposed improved FastICA algorithm based on the overrelaxation factor, while maintaining the rate of convergence, relaxes the requirement of initial weight vector, avoids the unbalanced convergence, reduces the number of iterations, and improves the convergence performance.

Highlights

Electrocardiogram (ECG) is an important tool used by physicians for identifying abnormalities in the human heart activity [1]
The FastICA algorithm is sensitive to the initial weight vector, and different initial weight vectors may lead to different convergence performances of the algorithm
The improved FastICA algorithm was applied to fetal ECG signal extraction

Summary

Introduction

Electrocardiogram (ECG) is an important tool used by physicians for identifying abnormalities in the human heart activity [1]. Fetal ECG signal can reflect electrophysiological activity of the fetal heart. Physicians can detect in time fetal abnormalities during fetal development through the fetal ECG waveform analysis, such as fetal distress and intrauterine hypoxia. A small number of abnormal fetal ECG waveforms are a manifestation of congenital heart disease, for which early measures can be taken to reduce neonatal morbidity and mortality. One is the invasive scalp electrode method, which can directly measure the pure fetal ECG signal. It can only detect fetal ECG signal during the time of birth, and it is invasive so it may cause harm to the mother and the fetus.

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