不同滤波参数设定对脑电图波形及功率谱的影响

EEG waveform and spectrum-power analysis under different settings of filter parameter

目的 探讨不同滤波设定对于脑电图波形及功率谱的具体影响。方法 选取癫痫患者22例作为病例组,选取性别、年龄匹配的健康人30名作为对照组。分别采集其常规脑电图,病例组选取包含较多癫痫样波的脑电图,对照组选取无任何异常波形脑电图。通过视检分析及功率谱分析,对比不同滤波参数设定下两组脑电波形及功率谱差异。结果 视检分析结果显示:高频滤波降低对于脑电图快波成分产生影响,并可能扭曲、削减尖波、棘波;低频滤波增高对于脑电图整体背景及慢波活动产生影响,并可能使得部分慢波波幅、形态发生变化。功率谱分析结果显示:组间分析显示0.5~70 Hz条件下两组之间主要差异体现于θ及α_(3)频段上;在中央区随着高频滤波减低,高频频段(α_(3)、γ_(1)、γ_(2))差异逐渐减低或消失,在其余脑区随着低频滤波的升高,δ频段逐渐显现出差异。组内额枕差异分析显示,脑电正常组在0.5~70 Hz条件下额区与枕区差异主要体现于θ、γ_(1)及γ_(2)频段上,随着高频滤波减低,高频频段(γ_(1)、γ_(2))差异逐渐减低或消失,而随着低频滤波升高,δ频段出现差异;脑电异常组在0.5~70 Hz条件下额区与枕区差异主要体现于γ_(1)及γ_(2)频段上,并随着高频滤波的减低,高频频段差异逐渐减低或消失。结论 研究结果表明,滤波设定对于脑电图结果具有显著的影响。在临床应用当中,我们应当严格以0.5~70 Hz带通滤波设定为标准。

Objective To explore the change of EEG waveform recorded by clinical EEG under different filtering parameters.Methods 22 abnormal EEG samples of epilepsy patients with abundant abnormal waveforms recorded in Peking University first hospital were selected as the case group(abnormal group),and 30 normal EEG samples of healthy people with matched sex and age were selected as the control group(normal group).Visual examination and power spectrum analysis were then performed to compare the difference of wave forms and spectrum power under different settings of filter parameter between the two groups.Results The results of visual examination show that,lower highfrequency filtering has an effect on the fast wave composition of EEG and may distort and reduce the spike wave.Higher low-frequency filtering has an effect on the overall background and slow wave activity of EEG and may change the amplitude morphology of some slow waves.The results of power spectrum analysis show that,Compare the difference between the EEG normal group and the abnormal group,the main difference under the settings of 0.5-70Hz was on the θand α_(3) frequency band,different brain regions were slightly different.In the central region,the difference in the high frequency band(α_(3),γ_(1),γ_(2)) decreases or disappears with the decrease of the high frequency filtering.In the rest of the brain,the difference in the δ band appears gradually with the increase of the low frequency filtering.Compare the difference between frontal area and occipital area under different filter set,for the normal group,under the settings of 0.5 ~ 70 Hz,the difference between two regions is mainly on the θ,γ_(1) and γ_(2) band.When high frequency filter reduces,the difference between two regions on high frequency band(γ_(1),γ_(2)) are gradually reduced or disappeared.And when low frequency filter increases,the difference on δ band appears.For the abnormal group,the difference between frontal and occipital region under the settings of 0.5 ~ 70 Hz is mainly on γ_(1) and γ_(2) bands.When the high-frequency filter decreases,the difference between two regions on high-frequency bands are gradually decreased or disappeared.All the results can be corrected by FDR.Conclusion The results show that the filter setting has a significant influence on EEG results.In clinical application,we should strictly set 0.5 ~ 70 Hz bandpass filtering as the standard.