Chapter 7

Three-dimensional Color
and Power Doppler Ultrasonography
of the Fetal Cardiovascular System
Rabih Chaoui, Karim D. Kalache

Introduction Advantages of Power Doppler

for 3D Rendering
The recent development of fast processors has en-
Both color and power Doppler ultrasonography are
abled ultra-rapid calculation and rendering of 3D
applied in vessel visualization, and practically both
images and the advent of real-time 3D (also called
can be used for 3D visualization. Power Doppler has,
4D) ultrasonography. Moreover, using newer systems,
however, various advantages over conventional color
fetal structures can now be visualized in different
Doppler [8, 9] that make it optimal for the 3D mode:
modes including the surface-, the maximum-, the
1. Sensitivity in flow detection: amplitude of Doppler
minimum-, and the ªX-rayº mode. The fetal vascular
signals instead of their frequency shift is analyzed
anatomy can be examined by using color Doppler
in power Doppler and this was shown to be three
and power Doppler ultrasound, power Doppler being
to five times more sensitive than conventional col-
superior to color Doppler in visualizing small vessels
or Doppler in visualizing small vessels and low
with low flow; however, the spatial course of the ves-
flows [8].
sels in the human body is best evaluated using 3D ul-
2. Improved noise differentiation: in power Doppler,
trasonography. By combining power Doppler and 3D
noise signals are encoded in a uniform color;
techniques it is possible to study the fetal and placen-
hence, it is possible to turn the gain all the way
tal vessels in relation to surrounding anatomic struc-
up, which fills the entire image with noise, and the
tures.
vascular signal will still be distinguishable.
Potential fields of application in obstetrics have
3. Better edge definition: power Doppler has a better
been reported in the past several years either as sin-
edge definition in displaying flow. This is because
gle case reports [1±5] or small series [6, 7]. This
color samples which extend partially beyond the
chapter reviews the technical background and poten-
edges are shown in a different color due to the
tial fields of application in obstetrical ultrasound.
lower signal amplitude.
4. Detection of flow orthogonal to beam: power Dop-
Technical Background pler is able to detect flow at right angles to the
beam. The amplitudes of the positive and negative
Equipment components of the flow tend to add up, resulting
in a powerful signal.
The few commercially available 3D systems have an
integrated 3D power Doppler ultrasonography (3D
PDU) feature as well, but there are also external Principle of Data Acquisition,
workstations adaptable to the different ultrasound Image Rendering, and Display
systems, offering offline postprocessing analysis and
evaluation. Most of our expertise we report in this The two main aspects which have to be considered
chapter was acquired by using the Voluson 730 Ex- when using a 3D imaging system are given below.
pert system (General Electrics-Kretztechnik, Zipf,
Austria) with an integrated on-line evaluation of vol- Volume Data Acquisition, Image Rendering,
ume rendering. Broadband curvilinear transducers and Display
with frequencies ranging between 4±8 MHz for the 1. During volume data acquisition the information is
abdominal probe and 5±9 MHz for the vaginal probe stored within a volume of interest. The acquired
were used. volume is a sequence of a pre-defined number of
2D slices (Fig. 7.1). The system assesses the spatial
information of the structures in relation to each
other in the different 2D images and allows a 3D
86 R. Chaoui, K. D. Kalache

Fig. 7.1. Several longitudinal views are necessary to visual- (UV) with ductus venosus (DV), and the descending aorta
ize the different vessels in the upper abdomen such as the (Ao). Compare with Fig. 7.2
hepatic veins (HV), inferior vena cava (IVC), umbilical vein

sufficient knowledge about how vessels are best vi-

sualized using power Doppler is a prerequisite to
obtaining a good-quality 3D power Doppler image.
Even if the method is very sensitive and allows the
imaging of small vessels, the optimization of pulse
repetition frequency (PRF), filter, insonation angle,
and persistence are of major importance. The PRF
and filter have to be set as high as necessary in or-
der to visualize only the vessels of interest, since
superimposed vessels may lead to confusion and
complicates orientation within the 3D volume.
Neighboring vessels or noise signals interfering
with the region of interest can be erased during
off-line reconstruction; however, good quality of
the original volume is essential for an optimal ren-
dering.
2. Image rendering is the process of creating a 3D re-
Fig. 7.2. Longitudinal view of thorax and upper abdomen. presentation of the parameters of interest. Generally,
Three-dimensional power Doppler rendering allows visuali- the principle used is the ªplanar geometric projec-
zation of all vessels described in Fig. 7.1 and their relation- tionº of the 3D image, i.e. a 2D image representing
ship to one another the 3D data as seen in the figures of this chapter.
The virtual impression of the third dimension is
generally given by the on-line rotation of the image
rendering (Fig. 7.2). Detailed gray-scale informa- on the screen and by different shadowing of anterior
tion is often not essential and lowers the quality of and posterior structures. Different color maps can
the rendered 3D power Doppler image; therefore, be used as well as various post-processing features

Fig. 7.3. Combined solid and 3D PDU mode with increasing transparency from left to right in a fetus with ascites
a Chapter 7 Three-dimensional Color and Power Doppler Ultrasonography of the Fetal Cardiovascular System 87

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

Fig. 7.4. Three-dimensional PDU images of cord insertion shown entering the placenta with the surface vessels
in anterior wall placenta. The umbilical cord (arrow) is diverging from the site of insertion
88 R. Chaoui, K. D. Kalache

Table 7.1. Conditions of the umbilical vessels in which 3D

power Doppler might be of some benefit

Placenta previa
Vasa previa
Insertio velamentosa
Connecting vessels in twin pregnancies (TTTS)
Vessel architecture in intrauterine growth restriction
Single umbilical artery
Nuchal cord
Torsion of umbilical vessels
True and false knot

Fig. 7.5. Placenta with central insertion of the umbilical

cord as demonstrated with 3D color Doppler ultrasonogra-
phy. There is a single umbilical artery (A). Umbilical vein (V)

Fig. 7.8. Three-dimensional PDU view of the lower abdo-

men and pelvis of a normal 23-gestational-week fetus
demonstrating both umbilical arteries converging toward
the anterior abdominal wall

Fig. 7.6. Three-dimensional PDU of a nuchal cord in a 23-

week-old fetus

Fig. 7.7. False knot in the free

loop of the umbilical cord in
prenatal 3D PDU and postnatal
finding
a Chapter 7 Three-dimensional Color and Power Doppler Ultrasonography of the Fetal Cardiovascular System 89

Table 7.2. Conditions for potential 3D power Doppler ap-

plication in the abdominal region

Abnormal cord insertion on the abdomen (omphalocele,

gastroschisis), abnormal shape of the umbilical vein size
(varix or ectasia)
Ductus venosus agenesis with persistent right umbilical
vein
Agenesis of the portal vein
Abdominal vessels in malformations, congenital dia-
phragmatic hernia, severe ascites, etc.
Abnormal course of vessels in isomerism, i.e., interrup-
tion of inferior vena cava with azygous continuity
Single umbilical artery and abnormalities in lower abdo-
men

Renal Vessels
Fig. 7.9. In the same view as Fig. 7.8, 3D PDU demon- The renal vascular tree is best visualized in a coronal
strates in this case an agenesis of the left umbilical artery. plane (Fig. 7.11). Depending on velocity scale setting,
Only one (dilated right) artery can be seen in its course to vessels can be seen from the main artery with some
the umbilical ring ramifications to the peripheral cortical vessels includ-
ing arteries and veins. The visualization of renal ves-
cava, and the abdominal aorta. Using this technique sels is known to increase the accuracy of diagnosis of
it is also possible to display the normal course of kidney malformations in the fetus. The examiner
umbilical arteries around the urinary bladder should be, however, aware of pitfalls such as the vi-
(Fig. 7.8). Since Doppler studies of the ductus veno- sualization of the ventrally situated abdominal ar-
sus in growth-restricted fetuses is becoming an im- teries (inferior mesenteric artery and vessels from ce-
portant field in prenatal medicine, abnormalities of liac trunk) that can be misinterpreted as renal ar-
the intrahepatic venous system are frequently de- teries. Conditions in which 3D PDU could be of diag-
tected (Fig. 7.10) [16]. This anatomical region is, nostic value are listed in Table 7.3.
however, complex, and it has been shown that 3D
Power Doppler can help in the differentiation between
anomalies (Table 7.2).

Fig. 7.10. Abnormal course of the intraabdominal umbilical vein and ductus venosus in a fetus with early hydrops at
13 weeks
90 R. Chaoui, K. D. Kalache

Fig. 7.11. A dorsal view to the fetus in 3D showing the and the bifurcation of both renal arteries. Ductus venosus
spine and both kidneys. The progressive visualization of is connected directly to the IVC
power Doppler demonstrates the descending aorta (Ao)

Table 7.3. Renal anomalies amenable to 3D power Dop- approach enables the visualization of the pericallosal
pler application artery with its ramifications (Fig. 7.13) [17]. By select-
ing a lower velocity scale it is possible to obtain im-
Agenesis of one or both kidneys pressive images of the cerebral veins and the sagittal si-
Horseshoe kidney
nus. Conditions with possible benefit of 3D power
Pelvic kidney
Abnormal vessel course in dysplastic renal anomalies Doppler, such as vein of Galen aneurysm (Fig. 7.14)
and others, are listed in Table 7.4.

Intracranial Vessels
As with color Doppler two main vascular regions can
be examined in 3D mode depending on the insonation
plane. A transversal insonation allows easy reconstruc-
tion of the circle of Willis (Fig. 7.12), whereas a sagittal

Fig. 7.13. Sagittal approach insonation of the brain en-

ables the demonstration of the pericallosal artery arising
from the anterior cerebral artery

3
Fig. 7.12. Circle of Willis as demonstrated with 3D PDU,
with the anterior (ACA), middle (MCA), and posterior (PCA)
cerebral arteries
a Chapter 7 Three-dimensional Color and Power Doppler Ultrasonography of the Fetal Cardiovascular System 91

Table 7.5. Conditions for potential 3D power Doppler ap-

plication in the pulmonary region

Cystic lung malformations

Congenital diaphragmatic hernia
Bronchopulmonary sequestration
Vessel anatomy or ramification in lung hypoplasia

sessed even by a less experienced examiner. Potential

fields of interest include the analysis of the 3D vessel
architecture in cystic lung malformations, congenital
diaphragmatic hernia, and in bronchopulmonary se-
questration. In the latter condition 3D power Doppler
facilitates the visualization of the abnormal systemic
vessel that feeds the sequester. Application fields are
Fig. 7.14. Three-dimensional PDU of a vein of Galen aneu- listed in Table 7.5.
rysm at 22 weeks gestation with the dilated vessel be-
tween the hemispheres and in the posterior fossa Fetal Tumors or Aberrant Vessels
Aberrant vessels can be visualized in the presence of
Table 7.4. Conditions for potential 3D power Doppler ap- several malformations such as choriangioma, lymph-
plication in the intracranial region angioma sacrococcygeal teratoma (Fig. 7.15), and
acardiac twin. The visualization of the vascular pat-
Abnormal anterior cerebral artery in agenesis of the cor-
pus callosum tern of fetal tumors is not only interesting because of
Aneurysm of the vein of Galen
Severe cerebral malformations (holoprosencephaly,
hydrocephaly, encephalocele, etc.) Table 7.6. Conditions for potential 3D power Doppler ap-
plication in tumors and aberrant vessels

Chorangioma
Teratoma
Lung Vessels Acrania (TRAP)
Proximal and peripheral lung arteries and veins can Hemangioma
Renal tumors
be seen from their origin to the peripheral pulmo-
Cardiac rhabdomyoma
nary segments. Especially the right lung can be as-

Fig. 7.15. Three-dimensional surface

and 3D PDU images of a sacrococcy-
geal teratoma at 22 weeks gestation.
The tumor is not highly vascularized
92 R. Chaoui, K. D. Kalache

Fig. 7.16. Three-dimensional PDU of a normal four-cham- with the right side, there is a muscular ventricular septal
ber view (left) with right and left atria (RA, LA), right and defect (VSD) connecting both ventricles
left ventricles (RV, LV), and the aortic root. In comparison

Fig. 7.17. Three-dimensional PDU of a four-chamber view Fig. 7.18. Aortic arch with the origin of the cephalic ves-
in a fetus with a hypoplastic left heart syndrome. Blood sels: the innominate (brachiocephalic) artery; the left com-
flow enters from the right atrium (RA) into the right ventri- mon carotid artery (LCC); and the left subclavian artery (LS)
cle (RV), but no flow is seen within the left ventricle (LV).
LA left atrium

tions. According to our experience we think that 3D

their risk of cardiac failure due to the presence of ar- PDU can be helpful in fetal cardiology in the near fu-
teriovenous fistulae, but also to assess compression ture and might facilitate the assessment of spatial ar-
or shifting of neighboring organs. Table 7.6 gives a rangement of the heart chambers including their size
summary of these fields of interest. and shape (Figs. 7.16, 7.17) as we demonstrate in
some of the figures in this chapter. Another possible
application field is an easier assessment of the course
Heart and Great Vessels
of the great vessels (Fig. 7.18). Crossing of vessels vs
The 3D rendering of the heart and the great vessels is parallel course (Fig. 7.19), abnormal course as seen
still a challenge to fetal ultrasound. Reliable volumes in double aortic arch, right arch with a sling, or sim-
are still difficult to obtain under routine scan condi- ply tortuous hypoplastic aorta or pulmonary artery
a Chapter 7 Three-dimensional Color and Power Doppler Ultrasonography of the Fetal Cardiovascular System 93

Fig. 7.19. Great vessels of a normal fetus (left) and a fetus the connection of the ductus arteriosus (DA) at the level of
with transposition of the great arteries (right). In the left the isthmus (ISTH). In transposition both vessels are parallel
image the crossing of the vessels is recognized with the and the aorta is on the right side of the pulmonary trunk
course of the aorta under the pulmonary trunk (TP) and

Fig. 7.20. A normal fetus (left) compared with a fetus with interruption of the inferior vena cava (star), which is absent
left isomerism (polysplenia; right): On the left the inferior on 3D PDU. Venous blood from the inferior part of the
vena cava is seen entering the heart and on the right side body returns via the azygos vein, which is dilated and seen
of the aorta the tiny azygos vein is recognized connecting side by side near the aorta
with the superior vena cava. In left isomerism there is an

Table 7.7. Conditions for potential 3D power and color in different anomalies may represent future applica-
Doppler application in fetal echocardiography tion fields [18, 19]. Venous anomalies could be of
further interest in the future (Fig. 7.20). Table 7.7
Anomalies of the four chambers summarizes some of these fields of interest.
Abnormal atrioventricular connection
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