Research on the developmental changes of central nervous system in the fetus using magnetocardiography and magnetoencephalography

为了评价胎儿中枢神经系统功能发育，我们首先根据胎儿心电图（fMCG）获得的RR间期数据集分析胎儿心率变异性，记录胎龄20-40周的无并发症胎儿的fMCG，并应用功率谱分析计算低频带（LF）的功率，高频带（HF）和LF/HF比。结果表明，LF（交感神经活动）的功率随胎龄显著增加，尽管HF（副交感神经活动）的功率在此期间保持不变。LF/HF比值也随着胎龄的增加而成比例增加，表明妊娠后期交感神经占主导地位。因此，fMCG被认为是评价胎儿自主神经系统或胎儿健康的有用方法，因为R波的检出率和时间分辨率都很高。 关于我们 胎儿脑的IC场。胎儿脑磁图（fMEG）的检测一直被认为是非常困难的，因为fMEG信号的幅度比fMICG的幅度弱得多，几乎在10 μ T单位的水平<-14>，并且因为信号平均技术由于信号的非周期性质而难以应用。为了提高fMEG的记录成功率，我们改进了SQUID系统的传感器，并实现了&lt;10 fT/μ s的空间分辨率<Hz>。用声脉冲（频率0.5或1 KHz，幅度70- 100dB，宽度50 msec）刺激胎儿颅骨，刺激频率0.5Hz，持续8 min，记录胎儿脑磁图。使用这种方法，在新生儿出生后立即在脉搏后120毫秒处检测到MEG信号的峰值，并且在婴儿脉搏后120和220毫秒处检测到两个峰值。然而，即使在足月胎仔中也未确定明显的fMEG峰。我们的结论是，需要进一步改进SQUID系统的灵敏度，听觉刺激和记录方法，以及数据的后处理，以使用fMEG评估胎儿大脑的功能发育或成熟。少

To assess the functional development of fetal central nervous system, we first analyzed heart rate variability in the fetus based on the data set of RR intervals obtained by fetal megnetocardiography (fMCG), fMCG was recorded in uncomplicated fetuses with the gestational age of 20-40 weeks, and power spectral analysis was applied to calculate the power of the low frequency band (LF), high frequency band (HF) and LF/HF ratio. Consequently, it was demonstrated that the power of LF (sympathetic activity) increases significantly with the gestational age although that of HF (parasympathetic activity) remained unchanged during the period. The LF/HF ratio also increases in proportion with the gestational age, indicating sympathetic dominance in later gestation. Thus, .fMCG is recognized as useful methodology to evaluate fetal autonomic nervous system or fetal well-being, as the detection rate of R waves and the time resolution are very high.Then, we attempted to measure auditory evoked magnet … More ic fields of the fetal - brain. The detection of fetal megnetoencephalogram (fMEG) has been considered very hard because the magnitude of fMEG signals is much weaker than that of fMlCG, almost at the level of units of 10^<-14> Tesla, and because signal averaging technique is difficult to apply due to non-cyclic nature of the signals. To improve the success, rate of recording fMEG, we refined the sensors of the SQUID system and realized spatial resolution of <10 fT/√<Hz>. fMEG was recorded over the site of fetal skull on maternal abdomen under stimulation with acoustic pulses (frequency, 0.5 or 1KHz ; magnitude, 70-100 dB ; width, 50 msec) with a stimulus frequency of 0.5 Hz for 8 min. The signals obtained were averaged triggered by the acoustic pulse. With this methodology, a peak of MEG signal was detected at 120 msec after the pulse in neonates immediately after birth, and two peaks were detected at 120 and 220 msec after the pulse in infants. However, no apparent fMEG peaks were determined for fetuses even in full term. We concluded that further improvement of sensitivity of the SQUID system, auditory stimulation and recording methods, and post processing of the'data would be required to assess the functional development or maturation of the fetal brain using fMEG. Less