Conversion of umbilical arterial Doppler waveforms to cardiac cycle triggering signals: A preparatory study for online motion-gated three-dimensionalfetal echocardiography

To remove motion artefacts, a device was built to convert "noisy" umbilical arterial Doppler waveforms (UADWs) from an ultrasound (US) system into sha rp ECG R-wave-like cardiac cycle triggering signals (CCTSs). These CCTSs we re then used to gate a simultaneous (online) 3-D acquisition of sectional f etal echocardiograms from another US system. To test the conversion perform ance, a study was carried out in sheep fetal twins. Pulmonary arterial flow waveforms (PAFWs) from implanted probes were traced, in the meantime, to d etermine the reference cardiac cycle. Interference caused by running the tw o nonsynchronised US systems was controlled to three degrees (not-noticeabl e, moderate, and severe), together with high (greater than or equal to 40 c m/s) and low (< 40) flow velocities on UADWs. The conversion efficiency, as sessed by the percentage of UADWs converted into CCTSs, was in the range of 83% to 100% for not-noticeable and moderate interference, and 0% to 71% fo r severe interference. The triggering accuracy, assessed by [(time lag mean between the onsets of PAFWs and corresponding CCTSs) - (its 99% confidence level)] <divided by> the mean, was 90% to 96% for the not-noticeable inter ference high- and low-flow groups and for the moderate interference high-ho w group; 19% to 93% for the moderate interference low-flow group; and from not obtainable up to 90% for the severe interference groups. The results sh ow that UADWs can be used as a satisfactory online motion-gating source eve n in the presence of moderate interference. The major problems are from sev ere interference or moderate interference with low-flow velocity, which can be minimised/eliminated by the integration of the individual systems invol ved. (E-mail: jdeng@medphys.ucl.ac.uk) (C) 2001 World Federation for Ultras ound in Medicine & Biology.