Schneider U, Schleussner E, Haueisen J, Nowak H, Seewald H J
Department of Obstetrics, University Hospital, Jena, Germany.
Brain Topogr. 2001 Fall;14(1):69-80. doi: 10.1023/a:1012519923583.
Magnetoencephalography (MEG) using auditory evoked cortical fields (AEF) is an absolutely non-invasive method of passive measurement which utilizes magnetic fields caused by specific cortical activity. By applying the exceptionally sensitive SQUID technology to record these fields of dipolar configuration produced by the fetal brain, MEG as an investigational tool could provide new insights into the development of the human brain in utero. The major constraint to this application is a very low signal-to-noise ratio (SNR) that has to be attributed to a variety of factors including the magnetic signals generated by the fetal and maternal hearts which inevitably obscure a straightforward signal analysis. By applying a new algorithm of specific heart artefact reduction based on the relative regularity of the heart signals, we were able to increase the chance of extracting a fetal AEF from the raw data by the means of averaging techniques and principle component analysis. Results from 27 pregnant, healthy women (third trimester of their uncomplicated pregnancy) indicate an improved detection rate and the reproducibility of the fetal MEG. We evaluate and discuss a-priori criteria for signal analyses which will enable us to systematically analyze additional limiting factors, to further enhance the efficiency of this method and to promote the assessment of its possible clinical value in the future.
利用听觉诱发皮层场（AEF）的脑磁图（MEG）是一种绝对无创的被动测量方法，它利用特定皮层活动产生的磁场。通过应用极其灵敏的超导量子干涉装置（SQUID）技术来记录胎儿大脑产生的这些偶极配置场，MEG作为一种研究工具可以为子宫内人类大脑的发育提供新的见解。该应用的主要限制是非常低的信噪比（SNR），这必须归因于多种因素，包括胎儿和母亲心脏产生的磁信号，这些信号不可避免地会干扰直接的信号分析。通过应用一种基于心脏信号相对规律性的特定心脏伪影减少新算法，我们能够通过平均技术和主成分分析从原始数据中提取胎儿AEF的机会增加。来自27名健康孕妇（妊娠晚期，无并发症）的结果表明胎儿MEG的检测率和可重复性有所提高。我们评估并讨论信号分析的先验标准，这将使我们能够系统地分析其他限制因素，进一步提高该方法的效率，并促进对其未来可能临床价值的评估。
