Suppression of interference and artifacts by the signal space separation method
Suppression of interference and artifacts by the signal space separation method
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DOI：
10.1023/b:brat.0000032864.93890.f9
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发表时间：
2004-06-01
期刊：
影响因子：
2.7
通讯作者：
Simola, J
中科院分区：
文献类型：
--
作者：
Taulu, S;Kajola, M;Simola, J
具有数百个通道的多通道测量对无旋度矢量场进行过采样，就像无源体积中的磁场一样。这是基于磁标量势的拉普拉斯方程引起的约束；在源体积之外，信号在空间频带上受到限制。拉普拉斯方程的函数解使人们能够分离从包围感兴趣源的球体中产生的信号，例如，大脑中的电流，来自磁干扰。信号空间分离 (SSS) 是通过计算函数展开式的每一项的单独基向量来创建覆盖所有可测量信号向量的信号基来完成的。由于 SSS 基础对于所有实际传感器布置都是线性无关的，因此任何信号向量都具有独特的 SSS 分解，其中针对感兴趣的信号和来自感兴趣体积之外的信号具有单独的系数。因此，SSS基础提供了一种优雅的方法来消除外部干扰。与设备无关的 SSS 系数可用于将感兴趣的信号转换为虚拟传感器配置。通过将其建模为传感器阵列围绕静态物体的运动，这也可以用于补偿由物体运动引起的失真。依赖于分解的设备还使得能够使用自愿头部运动来记录生理直流现象。当与特性设计的传感器阵列一起使用时，SSS 不会影响感兴趣信号的形态或信噪比。
Multichannel measurement with hundreds of channels oversamples a curl-free vector field, like the magnetic field in a volume free of sources. This is based on the constraint caused by the Laplace's equation for the magnetic scalar potential; outside of the source volume the signals are spatially band limited. A functional solution of Laplace's equation enables one to separate the signals arising from the sphere enclosing the interesting sources, e.g. the currents in the brain, from the magnetic interference. Signal space separation (SSS) is accomplished by calculating individual basis vectors for each term of the functional expansion to create a signal basis covering all measurable signal vectors. Because the SSS basis is linearly independent for all practical sensor arrangements, any signal vector has a unique SSS decomposition with separate coefficients for the interesting signals and signals coming from outside the interesting volume. Thus, SSS basis provides an elegant method to remove external disturbances. The device-independent SSS coefficients can be used in transforming the interesting signals to virtual sensor configurations. This can also be used in compensating for distortions caused by movement of the object by modeling it as movement of the sensor array around a static object. The device-in dependence of the decomposition also enables physiological DC phenomena to be recorded using voluntary head movements. When used with property designed sensor array, SSS does not affect the morphology or the signal-to-noise ratio of the interesting signals.