[The 1MHz C-W Doppler device with an adaptive equalizer for fetal heat rate monitoring during labor].
A new 1MHz continuous wave Doppler device with adaptive digital data processing was introduced to fetal heart rate monitoring during labor. Frequency characteristics of three different continuous wave Doppler devices (2MHz, 1MHz, and 455kHz) were evaluated by FFT analysis, after triggering at the QRS peaks of simultaneously recorded fetal scalp ECG. By three dimensional FFT display, the 1MHz carrier frequency was found to be optimal because of its improved penetration and coverage of a wider area, than with 2MHz and 455kHz. It was obvious that the 1MHz signal provided simplified wave form patterns, and this was much more convenient in detecting the individual valve or flow signal originating in the fetal heart. However, the study revealed that at 455kHz, which was theoretically a compatible figure considering the size and the stroke of the fetal heart, the nature of Doppler signal was different from those at a higher frequency, suggesting that it is inconvenient for exact determination of the fetal heart rate. Another point to emphasize is the application of an adaptive equalizer. This equalizer gave a constant configuration of the Doppler signal, by calculating the average output level in the amplitude and frequency range during a given time interval. By this newly-devised specific filtering, the individual valve or flow component could be easily discerned. This analysis showed that the combination of a 1MHz Doppler device and an adaptive equalizer to be the best device for fetal heart rate monitoring during labor.
D001330:Electronic Data Processing; D005260:Female; D005323:Fetal Monitoring / Q000379:methods*; D006340:Heart Rate, Fetal; D006801:Humans; D007743:Labor, Obstetric; D011247:Pregnancy; D012984:Software; D014463:Ultrasonography / Q000295:instrumentation*