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a Chapter 7 Three-dimensional Color and Power Doppler Ultrasonography of the Fetal Cardiovascular System 87
such as changing the brightness, threshold, or
transparency of color. The examiner can furthermore
decide whether only vessels of interest are to
be visualized or if it is important to have the information
of the surrounding structures as well (socalled
glass-body rendering). The system allows
the examiner to switch progressively between surface
and transparent mode, which gives the impression
that the vascular tree shines through the surrounding
structures (Fig. 7.3).
Limitations of 3D Power Doppler
in Prenatal Ultrasound
Similar to other 3D modes, fetal movements are a
major cause of artifacts. Other limitations specific to
the method are related to the regions of interest and
neighboring vessel. In most cases the examiner is
choosing a compromise between the vessels of interest
with their ramifications and the overlapping from
neighboring vessels. Most limitations are still at the
level of the heart, where overlapping of color from
adjacent structures can limit the understanding of the
image. Pulsations of the heart during data acquisition
are still difficult to overcome, but the use of a quick
sweep by reducing image quality and increasing persistence
can reduce these artifacts [3].
Clinical Application
Conventional color Doppler and power Doppler ultrasound
are both useful in the assessment of fetal abnormalities
involving the cardiovascular system [12].
Application of color Doppler is not only of benefit in
the assessment of fetal cardiac anomalies [13, 14], but
also for completing diagnosis in many extracardiac
conditions [12]. The 3D PDU technique allows spatial
analysis of fetal vessels in relationship to their surrounding
anatomic structures. In a recent study [6]
we examined the application of 3D PDU in prenatal
diagnosis, by comparing 45 normal fetuses and 87
abnormal pregnancies with vascular abnormalities. In
the study we used a prototype system (HDI-3000,
Philips-ATL, Bothell, Wash.) and satisfactory image
information was obtained in only 64% (56 of 87) of
the abnormal cases. The following eight anatomical
regions were, however, found to be of interest:
1. Placenta
2. Umbilical cord
3. Abdomen
4. Kidneys
5. Lung
6. Brain
7. Fetal tumors
8. Heart and great vessels
The following section summarizes possible applications
of 3D color and power Doppler ultrasonography
in these different regions.
Umbilical Cord and Placenta
Placental vessels are best visualized in relation to the
umbilical cord insertion. The intraplacental vascular
tree can be visualized with this method [15]. The umbilical
cord can be rendered from its placental
(Figs. 7.4, 7.5) to its abdominal insertion including
the free loop (Figs. 7.6, 7.7) [6]. From our experience
it is the easiest structure to assess using 3D PDU
throughout pregnancy. Conditions in which 3D power
Doppler might be of some benefit are listed in Table
7.1.
Intraabdominal Vessels
Examination of the intraabdominal structures using
3D Power Doppler is best achieved when examining
the abdomen in a longitudinal plane. This approach
allows the visualization of the intraabdominal portion
of the umbilical arteries (Figs. 7.8, 7.9) and vein with
the ductus venosus (Figs. 7.2, 7.3), the portal system,
the hepatic veins, the splenic vessels, the inferior vena
Fig. 7.4. Three-dimensional PDU images of cord insertion
in anterior wall placenta. The umbilical cord (arrow) is
shown entering the placenta with the surface vessels
diverging from the site of insertion