Recent advances in the technology of color/power Doppler ultrasound have, in the clinical field of perinatology, contributed to successful visualization of both the maternal–fetal and postnatal circulations. However, problems still remain in the display of Doppler sono-angiography information. Vascular images demonstrated by conventional Doppler techniques tend to exaggerate the size of real vessels. In addition the morphological information detected and displayed by gray scale B-mode imaging may be lost by the overlying color or power Doppler signals. A new technology of ultrasound angiography termed ‘B-flow’ and produced by the LOGIQ700 (GE Medical Systems, Milwaukee, WI, USA) uses digitally encoding techniques to suppress tissue clutter and improve sensitivity for the direct visualization of blood reflectors. Since B-flow imaging reflects streams of intravascular red blood cells angle-independently, such blood streams can be identified with ease. The technique also makes it possible to visualize complex flow patterns inside small vessels. The B-flow image does not interfere with the information produced by B-mode because both techniques utilize the same spatial resolution and frame-rate. Figure 1 demonstrates umbilical blood flow by B-flow at 33 weeks of gestation. The presence of flow within the umbilical vein and arteries together with the extravascular component including Wharton's jelly can be clearly identified. Blood flow demonstrated by B-mode imaging in the umbilical cord of a 33 week fetus. Figure 2 demonstrates the anterior cerebral and pericallosal arteries in a neonate. Bilateral anterior cerebral arteries, which have never been distinguished by conventional color/power Doppler and previously have been depicted as a single vessel because of their close location, can be distinguished on a B-flow image as two parallel vessels. This new technology may provide a breakthrough in imaging perinatal vasculature and thus a new method of hemodynamic assessment in the fetus and neonate.
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Ritsuko K. Pooh (2000) studied this question.