Suppression of MR gradient artefacts on electrophysiological signals based on an adaptive real-time filter with LMS coefficient updates
Suppression of MR gradient artefacts on electrophysiological signals based on an adaptive real-time filter with LMS coefficient updates
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DOI：
10.1007/s10334-004-0093-1
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发表时间：
2005-03-01
影响因子：
2.3
通讯作者：
Felblinger, J
中科院分区：
文献类型：
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作者：
Abächerli, R;Pasquier, C;Felblinger, J
心电图 (ECG) 采集仍然是一个挑战，因为叠加在电生理信号上的梯度伪影只能部分去除。这些伪影的信号形状可能与 QRS 复合波类似，在患者监测和 MRI 的错误触发/门控过程中可能会导致误解。为了对其进行实时抑制，提出了一种自适应滤波器。自适应滤波器基于具有 LMS 系数更新的噪声消除器配置。噪声消除器的参考是与噪声心电图同时采集的三个梯度信号。使用 MR 安全心电图模拟器对患者和志愿者进行了测试。噪声消除器的性能是离线测量的，通过逐点操作模拟实时处理。为了创建最坏的情况，选择了具有强且快速切换梯度的临床序列。降噪滤波器在适应后将梯度伪影的峰值幅度降低了 80-99%，而不改变所需的 ECG 信号形状。 MR 梯度伪影的总平均功率估计减少 62-98%。所提出的滤波器能够减少由于实时应用和最坏情况下的强且快速切换梯度而产生的伪影。 ECG 的质量足够高，以至于可以使用标准单导联 QRS 探测器来门控/触发 MRI。对于永久性患者监测，需要进一步改进。
Electrocardiogram (ECG) acquisition is still a challenge as gradient artefacts superimposed on the electrophysiological signal can only be partially removed. The signal shape of theses artefacts can be similar to the QRS-complex, causing possible misinterpretation during patient monitoring and false triggering/gating of the MRI. For their real-time suppression, an adaptive filter is proposed. The adaptive filter is based on the noise-canceller configuration with LMS coefficient updates. The references of the noise canceller are the three gradient signals that are acquired simultaneously with the noisy ECG. Tests were done on patients, on volunteers and using an MR-safe ECG simulator. The noise canceller's performance was measured offline, simulating real-time processing by point-by-point operations. To create worst-case scenarios, clinical sequences with strong- and fast-switching gradients have been chosen. The noise-cancel ling filter reduces the gradient artefacts' peak amplitudes by 80-99% after adaptation, without changing the desired ECG signal shape. The estimated reduction of total average power of the MR gradient artefacts is 62-98%. The proposed filter is capable of reducing artefacts due to strong- and fast-switching gradients in real-time applications and worst-case situations. The quality of the ECG is sufficiently high that a standard one-lead QRS-detector can be used for gating/triggering the MRI. For permanent patient monitoring, further improvements are needed.