Wakai Ronald T, Lutter William J
Department of Medical Physics, University of Wisconsin, Madison 53706, USA.
IEEE Trans Biomed Eng. 2002 Oct;49(10):1214-7. doi: 10.1109/TBME.2002.803523.
We have developed a two-step procedure for signal processing of fetal biomagnetic recordings that removes cardiac interference and noise. First, a modified matched filter (MF) is applied to remove maternal cardiac interference; then, a simple signal space projection (SSP) is applied to remove noise. The key difference between our MF and a conventional one is that the interference template and the template scaling are derived from a signal that has been spatially filtered to isolate the interference, rather than from the raw signal. Unlike conventional MFs, ours is able to separate maternal and fetal cardiac complexes, even when they have similar morphology and overlap strongly. When followed by a SSP that preserves only the signal subspace, the noise is reduced to a low level.
我们已经开发出一种用于胎儿生物磁记录信号处理的两步程序，该程序可去除心脏干扰和噪声。首先，应用改进的匹配滤波器（MF）去除母体心脏干扰；然后，应用简单的信号空间投影（SSP）去除噪声。我们的MF与传统MF的关键区别在于，干扰模板和模板缩放是从经过空间滤波以分离干扰的信号中得出的，而不是从原始信号中得出的。与传统的MF不同，即使母体和胎儿心脏复合体具有相似的形态且强烈重叠，我们的MF也能够将它们分开。当随后进行仅保留信号子空间的SSP时，噪声会降低到较低水平。
