Some Investigations Facing Fetal ECG R Wave Detection

In general, the problems of fetal R-wave detection are mainly reflected in two aspects:On one hand, the fetal signal to noise ratio (fetal SNR) is too low. After removing its maternal ECG component from the abdominal ECG signal, the fECG may be buried in strong background noise. As a result, the fetal R-wave peaks are hard to be detected. On the other hand, either the maternal component is too small or the fetal component is too large for us to make right maternal R-wave detection directly, which finally leads to the false detection of the fetal R-waves.To address the above two problems of the fetal R-wave detection, some research works are conducted in this paper, shown as follows:(1) Many field experiments were carried out in the Obstetrics Branch of Nanjing General Hospital of Nanjing Military Command and 343 groups of abdominal ECG signal data were collected totally from pregnant women.(2)Based on the practical measured data, the distribution regularity of fECG SNRs was studied. The statistical result shows that the fECG SNRs are significantly higher in certain locations than others and provide an important reference for the placement of the electrode positions when detecting the fetal ECG. In addition, reasonable explanation is also provided to the statistical result by the theory of the fetal cardiac electrical axis and the phase delay.(3) First select one abdominal signal with higher maternal ECG SNR as a reference signal and detect the maternal R-wave peaks of this reference signal, which is easier. Then based on the detected maternal R-wave peak indexes, we detect the maternal R-wave peaks of the other signals, by means of local searching at the positions of the reference signal’s maternal R-wave peaks. For computer to accomplish the automatic local searching, we need to set up a reasonable local search range. So we study the regularity of position difference of the corresponding R-wave peaks between different point abdominal signals. Finally a statistical regularity is discovered that the range of the R-wave peak position will not exceed 30ms.(4) The abdominal signal with larger fetal ECG component or smaller maternal ECG component all will have more serious problems in its maternal R-wave peak detections. In order to solve these problems, on one hand the method of the wavelet decomposition and reconstruction for single-channel was optimized to improve the accuracy of the maternal R-wave detection. On the other hand, based on the R-wave detection results of the 8 channel signals, an error correction technique with multi-channel fusion is proposed to further increase the correct detection rates of all the 8 channel signals.This paper is divided into six chapters, Chapter 1 is an introduction, and Chapters 2-5 correspond to the above mentioned four research works. In Chapter 6, the main work of this paper was summed up, and introduced the shortcomings of the study and the prospects of the future work.