Strobach P, Abraham-Fuchs K, Härer W
Fachhochschule Furtwangen, Germany.
IEEE Trans Biomed Eng. 1994 Apr;41(4):343-50. doi: 10.1109/10.284962.
A two-pass adaptive filtering algorithm is proposed for cancellation of recurrent interferences such as the heart interference in biomedical signals. In the first pass, an average waveform in one period of the interference is estimated by event-synchronous (QRS-synchronous) averaging of the corrupted signal. In a second pass, an adaptive Schur recursive least squares (RLS) lattice filter is used to cancel the interference by using the event synchronously repeated estimated average waveform of the interference as an artificial reference signal. One key feature of this approach is that the ECG is only used for QRS synchronization and not directly as a reference signal for adaptive filtering. Thus the proposed algorithm can be applied to interference problems where ECG and true interference are almost synchronous but show considerably different waveforms. This is usually the case with the heart interference in biomedical signals. Both off-line and real-time implementations of the event synchronous interference canceller are described. The method is applied to the cancellation of the heart interference in magnetoencephalogram (MEG) signals and to the effective isolation of ventricular extrasystoles (VES) in magnetocardiogram (MCG) signals. Experimental results are shown. The new method typically attenuates the amplitudes of R-wave and T-wave interference components by an amplitude factor of 30 without influencing the MEG events of interest.
提出了一种双程自适应滤波算法，用于消除生物医学信号中的周期性干扰，如心脏干扰。在第一程中，通过对受干扰信号进行事件同步（QRS同步）平均来估计干扰一个周期内的平均波形。在第二程中，使用自适应舒尔递归最小二乘（RLS）格型滤波器，通过将事件同步重复估计的干扰平均波形用作人工参考信号来消除干扰。该方法的一个关键特性是，心电图仅用于QRS同步，而不直接用作自适应滤波的参考信号。因此，所提出的算法可应用于心电图与真实干扰几乎同步但波形差异较大的干扰问题。生物医学信号中的心脏干扰通常就是这种情况。描述了事件同步干扰消除器的离线和实时实现。该方法应用于消除脑磁图（MEG）信号中的心脏干扰以及有效分离心磁图（MCG）信号中的室性早搏（VES）。展示了实验结果。新方法通常将R波和T波干扰分量的幅度衰减30倍，而不影响感兴趣的MEG事件。
