Chang Nathalie, Gulrajani Ramesh, Gotman Jean
Montreal Neurological Institute, McGill University, QC, Canada.
Clin Neurophysiol. 2005 Nov;116(11):2707-16. doi: 10.1016/j.clinph.2005.07.002. Epub 2005 Oct 7.
In the clinical interpretation of intracerebral EEGs, epileptic foci are commonly identified by visually analyzing the amplitude of the potentials. This is potentially misleading since electrodes record activity from several sources, but the nearest ones generate large amplitudes that can overpower distant sources. Our objective was to improve foci detection in intracerebral recordings by applying source localization methods.
Data were simulated by placing 3 sources in a semi-infinite medium near 3 intracerebral electrodes. Potentials were generated and contaminated with white and correlated noise. Two inverse problem algorithms, beamforming and RAP-MUSIC, were used to calculate equivalent dipoles.
Simulations for each noise types showed that the two methods detected the source locations accurately, with RAP-MUSIC reporting lower orientation errors. With correlated noise, beamforming reconstructed original source waveforms poorly. A spatial resolution analysis was performed, in which beamforming adequately distinguished sources separated by 1.2 cm, whereas RAP-MUSIC separated sources as close as 0.4-0.6 cm.
Both source localization methods proved useful in detecting the location of dipolar sources based on simulated intracerebral potentials. For all simulations, RAP-MUSIC was more accurate than beamforming.
It is possible to use source localization methods traditionally applied to scalp recordings for improving source detection from intracerebral recordings.
在脑内脑电图的临床解读中，癫痫病灶通常通过直观分析电位幅度来识别。这可能会产生误导，因为电极记录的是多个来源的活动，但距离最近的来源会产生较大幅度的电位，从而掩盖远处来源的电位。我们的目标是通过应用源定位方法来改善脑内记录中的病灶检测。
通过在靠近3个脑内电极的半无限介质中放置3个源来模拟数据。生成电位并加入白噪声和相关噪声。使用两种逆问题算法，即波束形成和RAP-MUSIC，来计算等效偶极子。
对每种噪声类型的模拟表明，这两种方法都能准确检测源位置，RAP-MUSIC报告的方向误差更低。在存在相关噪声的情况下，波束形成对原始源波形的重建效果较差。进行了空间分辨率分析，其中波束形成能够充分区分相距1.2厘米的源，而RAP-MUSIC能够区分相距仅0.4 - 0.6厘米的源。
两种源定位方法在基于模拟脑内电位检测偶极源位置方面都被证明是有用的。对于所有模拟，RAP-MUSIC比波束形成更准确。
有可能将传统应用于头皮记录的源定位方法用于改善脑内记录的源检测。
