Fetal MEG redistribution by projection operators
Fetal MEG redistribution by projection operators
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DOI：
10.1109/tbme.2004.827265
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发表时间：
2004-07-01
影响因子：
4.6
通讯作者：
Preissl, H
中科院分区：
文献类型：
--
作者：
Vrba, J;Robinson, SE;Preissl, H
胎儿脑磁图 (IMEG) 是在母体和胎儿心磁图存在较大干扰的情况下测量的。通过相应空间矢量的正交投影可以有效地衰减这种干扰。然而，投影算子会在传感器之间重新分配 fMEG 信号。尽管在正向解中可以很容易地解释重新分布，但 fMEG 信号拓扑的视觉解释却很困难。我们设计了一种通用的、与模型无关的方法来校正重新分布效应，该方法利用了这样的假设：我们知道在哪些通道中 MEG 应该可以忽略不计（这些通道远离已知的胎儿头部位置）。在 fMEG 可以用等效电流偶极子解释的简化情况下，也可以通过将偶极子拟合到 fMEG 信号来获得校正。校正后的 fMEG 信号拓扑对应于偶极子正向解，但没有正交投影。我们以实验测量的闪光诱发 fMEG 为例说明了重新分布校正。
The fetal magnetoencephalogram (IMEG) is measured in the presence of large interference from the maternal and fetal magnetocardiograms. This interference can be efficiently attenuated by orthogonal projection of the corresponding spatial vectors. However, the projection operators redistribute the fMEG signal among sensors. Although redistribution can be readily accounted for in the forward solution, visual interpretation of the fMEG signal topography is made difficult. We have devised a general, model-independent method for correction of the redistribution effect that utilizes the assumption that we know in which channels the MEG should be negligible (such channels are distant from the known fetal head position). In a simplified case where the fMEG can be explained by equivalent current dipoles, the correction can also be obtained from fitting the dipoles to the fMEG signal. The corrected fMEG signal topography then corresponds to the dipole forward solution, but without orthogonal projection. We illustrate the redistribution correction on an example of experimentally measured flash evoked fMEG.