Comparison between color Doppler cineloop- and conventional spectral Doppler-derived maximum velocity and flow in the umbilical vein

Objective: To compare the umbilical venous flow velocity derived from color Doppler cineloop recordings with that derived from conventional spectral Doppler in normal pregnancies. Method: In 18 uncomplicated pregnancies between 19 and 39 weeks' gestation, color Doppler was used to find the maximum velocity in the cross-sectional vessel area of a free-floating loop of the umbilical vein. The maximum velocity was determined using the software tool HDILab (Philips Medical Systems) after tracing the vessel area of interest. Conventional spectral Doppler was then used to determine the maximum velocity with the High-Q machine option. The cross-sectional area of the umbilical vein was determined using B-mode imaging and was subsequently used to determine the umbilical volume flow from both Doppler methods. Assuming a parabolic flow profile in the umbilical vein, the mean velocity is equal to half the maximum velocity. The fetal weight was estimated from fetal biometry using the four-parameter Hadlock formula. Results: Maximum velocity was significantly (P = 0.003) higher with color Doppler cineloop (14.3 ± 2.5 cm/s) compared with spectral Doppler (12.7 ± 3.2 cm/s). Therefore, using the same cross-sectional area for both methods, the umbilical blood flow was significantly higher (P = 0.001) with color Doppler cineloop (127.9 ± 59.0 mL/min) than it was with spectral Doppler (112.8 ± 54.1 mL/min). The umbilical blood flow expressed as volume flow per kg fetal weight was significantly (P = 0.01) higher with color Doppler cineloop (126.0 ± 57.0 mL/min/kg) than it was with spectral Doppler (115.0 ± 53.0 mL/min/kg). Conclusions: Umbilical venous flow velocity derived from color Doppler cineloops is approximately 10% higher than that derived from spectral Doppler-derived velocity. The reduced angle dependence of the color Doppler cineloop technique and the large sampling area of the cross-sectional vessel should allow better determination of the correct maximum velocity in the umbilical vein. Copyright

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