[Advanced system for real-time fetal breathing movements tracking using pulsed Doppler ultrasound]

Utilization of the fetal behavioral information in clinical medicine requires the development of an automated monitoring technique. As previously reported, the off-line signal processing of the low frequency Doppler signals by high accuracy displacement estimation made it possible to measure fetal breathing movements (FBM). However, there were several problems to solve before clinical application. We propose an advanced system that provides real-time calculation. The multi-channel pulsed doppler device was newly developed by modifying the Doppler ultrasound module of the cardiotocograph (CTG). A new signal processing algorithm was designed to produce real-time measurements. To improve the resolution, the backing module was attached to the probe. On-line signal processing produced a successful real-time and continuous calculation of displacement inside tissue. By means of an on-line 2/3 Hz high pass filter, the very low frequency noises and the artifacts derived from maternal respiration etc. were removed. The signal/noise ratio was obviously increased and the waves of fetal tissue movements due to FBM were easily recognized in real-time LCD outputs. Although there is a limitation in measuring accuracy as far as using modified CTG units, the results demonstrate that our system has commendable quality in FBM tracking.