Bai Xiaoxiao, He Bin
Department of Biomedical Engineering University of Minnesota, 7-105 BSBE, 312 Church Street SE, Minneapolis, MN 55455, USA.
Clin Neurophysiol. 2005 Sep;116(9):2037-43. doi: 10.1016/j.clinph.2005.06.001.
The purpose of the present study was to determine the number of the equivalent dipole sources corresponding to the scalp EEG using the information criterion method based on the instantaneous-state modeling.
A three-concentric-spheres head model was used to represent the head volume conductor. The Powell algorithm was used to solve the inverse problem of estimating the equivalent dipoles from the scalp EEG. The information criterion with different penalty functions was used to determine the dipole number. Computer simulations were conducted to evaluate effects of various parameters on the estimation of dipole number.
The present results suggest that the present method is able to estimate the number of equivalent current dipoles (ECDs) from instantaneous scalp EEG measurements, and that increase in the electrode number can improve the accuracy of estimation of the ECD number. For two ECDs, the best performance of estimation with 20% white noise were 85%, 92% and 94%, when 64, 128 and 256 electrodes are used, respectively. When there are 3 ECDs, the present results suggest that using 256 electrodes gave up to 82% estimation accuracy. The present simulation results also indicate that the accuracies of identification are similar when the minimum distance between dipoles is either 1 or 2 cm, which was used in the simulation. It was also found that the different penalty functions used in the information criterion method could have substantial influence on the estimation accuracy.
The present method can estimate the number of ECDs from instantaneous scalp EEG distribution for up to three dipoles.
The successful estimation of the number of ECDs will play an important role in expanding the applicability of dipole source localization to multiple sources.
本研究旨在基于瞬时状态建模，运用信息准则法确定与头皮脑电图相对应的等效偶极子源数量。
采用三同心球头模型来表示头部容积导体。运用鲍威尔算法解决从头皮脑电图估计等效偶极子的逆问题。使用具有不同惩罚函数的信息准则来确定偶极子数量。进行计算机模拟以评估各种参数对偶极子数量估计的影响。
目前的结果表明，该方法能够从瞬时头皮脑电图测量中估计等效电流偶极子（ECD）的数量，并且电极数量的增加可以提高ECD数量估计的准确性。对于两个ECD，在加入20%白噪声的情况下，当分别使用64、128和256个电极时，最佳估计性能分别为85%、92%和94%。当存在3个ECD时，目前的结果表明使用256个电极时估计准确率高达82%。目前的模拟结果还表明，在模拟中使用的偶极子之间的最小距离为1或2厘米时，识别准确率相似。还发现信息准则法中使用的不同惩罚函数可能对估计准确性有重大影响。
该方法可以从瞬时头皮脑电图分布中估计多达三个偶极子的ECD数量。
成功估计ECD数量将在将偶极子源定位的适用性扩展到多个源方面发挥重要作用。
