Department of Biomedical Signal Processing, Institute of Medical Technology and Equipment, Roosevelta 118, 41-800 Zabrze, Poland.
Biomed Eng Online. 2011 Oct 14;10:92. doi: 10.1186/1475-925X-10-92.
The currently used fetal monitoring instrumentation that is based on Doppler ultrasound technique provides the fetal heart rate (FHR) signal with limited accuracy. It is particularly noticeable as significant decrease of clinically important feature - the variability of FHR signal. The aim of our work was to develop a novel efficient technique for processing of the ultrasound signal, which could estimate the cardiac cycle duration with accuracy comparable to a direct electrocardiography.
We have proposed a new technique which provides the true beat-to-beat values of the FHR signal through multiple measurement of a given cardiac cycle in the ultrasound signal. The method consists in three steps: the dynamic adjustment of autocorrelation window, the adaptive autocorrelation peak detection and determination of beat-to-beat intervals. The estimated fetal heart rate values and calculated indices describing variability of FHR, were compared to the reference data obtained from the direct fetal electrocardiogram, as well as to another method for FHR estimation.
The results revealed that our method increases the accuracy in comparison to currently used fetal monitoring instrumentation, and thus enables to calculate reliable parameters describing the variability of FHR. Relating these results to the other method for FHR estimation we showed that in our approach a much lower number of measured cardiac cycles was rejected as being invalid.
The proposed method for fetal heart rate determination on a beat-to-beat basis offers a high accuracy of the heart interval measurement enabling reliable quantitative assessment of the FHR variability, at the same time reducing the number of invalid cardiac cycle measurements.
目前基于多普勒超声技术的胎儿监护仪器提供的胎儿心率（FHR）信号准确性有限。尤其明显的是，临床上重要特征——FHR 信号的可变性显著下降。我们的工作旨在开发一种新的超声信号处理技术，该技术可以以与直接心电图相当的精度来估计心动周期持续时间。
我们提出了一种新技术，通过在超声信号中多次测量给定心动周期，提供 FHR 信号的真实逐搏值。该方法包括三个步骤：自相关窗口的动态调整、自适应自相关峰值检测和逐搏间隔的确定。所估计的胎儿心率值和计算出的描述 FHR 可变性的指标与直接胎儿心电图获得的参考数据以及另一种 FHR 估计方法进行了比较。
结果表明，与目前使用的胎儿监护仪器相比，我们的方法提高了准确性，从而能够计算出描述 FHR 可变性的可靠参数。将这些结果与另一种 FHR 估计方法进行比较，我们表明在我们的方法中，有明显更少数量的测量心动周期被拒绝为无效。
提出的基于逐搏的胎儿心率确定方法提供了心动周期测量的高精度，能够可靠地评估 FHR 的可变性，同时减少无效心动周期测量的数量。
