von Ellenrieder Nicolás, Muravchik Carlos H, Wagner Michael, Nehorai Arye
Department of Electrical Engineering and the Laboratory of Industrial Electronics, Control, and Instrumentation, Faculty of Engineering, National University of La Plata, Buenos Aires 1900, Argentina.
IEEE Trans Biomed Eng. 2009 Mar;56(3):587-97. doi: 10.1109/TBME.2009.2008445.
We study the effect of the head shape variations on the EEG/magnetoencephalography (MEG) forward and inverse problems. We build a random head model such that each sample represents the head shape of a different individual and solve the forward problem assuming this random head model, using a polynomial chaos expansion. The random solution of the forward problem is then used to quantify the effect of the geometry when the inverse problem is solved with a standard head model. The results derived with this approach are valid for a continuous family of head models, rather than just for a set of cases. The random model consists of three random surfaces that define layers of different electric conductivity, and we built an example based on a set of 30 deterministic models from adults. Our results show that for a dipolar source model, the effect of the head shape variations on the EEG/MEG inverse problem due to the random head model is slightly larger than the effect of the electronic noise present in the sensors. The variations in the EEG inverse problem solutions are due to the variations in the shape of the volume conductor, while the variations in the MEG inverse problem solutions, larger than the EEG ones, are caused mainly by the variations of the absolute position of the sources in a coordinate system based on anatomical landmarks, in which the magnetometers have a fixed position.
我们研究头部形状变化对脑电图/脑磁图（MEG）正问题和逆问题的影响。我们构建了一个随机头部模型，使得每个样本代表不同个体的头部形状，并使用多项式混沌展开法，在假设该随机头部模型的情况下求解正问题。然后，当使用标准头部模型求解逆问题时，正问题的随机解用于量化几何形状的影响。用这种方法得出的结果对连续的一系列头部模型有效，而不仅仅适用于一组案例。随机模型由定义不同电导率层的三个随机表面组成，并且我们基于一组来自成年人的30个确定性模型构建了一个示例。我们的结果表明，对于偶极源模型，由于随机头部模型导致的头部形状变化对脑电图/脑磁图逆问题的影响略大于传感器中存在的电子噪声的影响。脑电图逆问题解的变化是由于体积导体形状的变化，而脑磁图逆问题解的变化大于脑电图的变化，主要是由基于解剖学标志的坐标系中源的绝对位置的变化引起的，在该坐标系中磁力计具有固定位置。
