基于小波变换的多普勒胎儿心率检测研究

Doppler Fetal Heart Rate Detection Based on Wavelet Transform

为了解决从超声多普勒胎儿心脏回波信号中提取胎音信号时,去除各种干扰和噪声的问题,分析了超声多普勒回波信号的特点,应用了基于小波变换的阈值去噪方法,并对该方法的去噪阈值和原始噪声方差的估计进行了研究.在实际应用中对该阈值算子的系数作了改进,使得该算法能根据实际信号的强度、噪声的方差以及分解的层数,自适应地得到不同尺度的去噪阈值.通过对实际超声多普勒回波信号的处理,信噪比比传统滤波法提高至少5倍以上,能有效地提取出胎儿心音信号,较准确地计算出胎儿心率值.

To remove noise when extracting fetal heart sound from Doppler fetal heart echo signal, the threshold denoising method based on wavelet transform is adopted according to the signal features, and the denoising threshold and the estimation for original noise variance are investigated to modify the coefficient of threshold operators for different scales based on actual signal intensity, the noise variance and the number of decomposition layers. This method has been employed to process actual Doppler fetal heart echo signal, the result verifies that the method enables to heighten the signal-to-noise ratio by five times than the traditional filter and accurately calculate fetal heart rate.