Technical aspects of ranged directional doppler: a new doppler method of fetal heart rate monitoring.

A new technique for clarifying the fetal heart Doppler signal (Ranged Directional Doppler) for fetal heart rate (FHR) monitoring has been developed. Ranged Directional Doppler enhances the signals of interest and, in addition, permits a separation of the Doppler signals generated by fast-moving structures of the fetal heart either toward or away from the transducer. The separation of the Doppler signals provides increased clarity and reduced baseline clutter. These Doppler signals may approach the fetal scalp ECG in signal-to-noise ratio, and they may provide a signal that allows more accurate external monitoring of long-term and short-term variability patterns of the FHR.