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a Chapter 34 Four-Dimensional B-Mode and Color Doppler Echocardiography of the Human Fetus 513
Fig. 34.9. Four-dimensional echocardiography in a fetus
with complete atrioventricular septal defect. The pyramidal
section has been cropped to show regurgitation (R) from
the right-sided component of V. AO aortic cross section.
(From [12])
One of the apparent limitations of the technique in
our preliminary assessment is the inability to use fetal
electrocardiography signals to trigger the volume acquisition
which is the approach utilized in assessing
the adult heart; however, as mentioned above, a simulated
heart rate can be used within the range of the normal
fetal heart rate with no visually detectable artifacts.
The other potential challenge in any fetal imaging is related
to fetal movements which may also interfere with
live 3D imaging; however, this is not a significant problem
in this system because of the very fast volume acquisition
in both B- and color Doppler modes.
Motorized Curved Linear-Array
System and Spatio-Temporal
Image Correlation
This is an advanced system essentially based on 3D image
reconstruction from sequentially acquired 2D
images (Voluson 730 Expert System, General Electric
Medical Systems, Kretztechnik, Zipf, Austria). The
transducer assembly encases a curved linear array of
transducer elements and a motor drive. The drive mechanism
allows an automated sweep of the target area to
generate 2D images sequentially constituting the volume
data set. This method is inherently inadequate
for fetal echocardiography because of fetal cardiac motion.
Development of the spatio-temporal correlation
technology (STIC), however, has resolved this issue.
An integral part of the 3D volume acquisition system,
STIC processing, determines the fetal heart rate
Fig. 34.10. Four-dimensional echocardiography in a fetus
with complete atrioventricular septal defect. a Two-dimensional
B-mode image of the lesion. The upper horizontal arrow
shows the ventricular septal defect; the lower horizontal
arrow shows the absence of the atrial septum. b Fourchamber
view cropped to show the common atrioventricular
valve (V) and the defect (asterisks). RA right atrium, LA
left atrium, RV right ventricle, LV left ventricle. (From [12])
from the systolic peaks of the fetal cardiac motion
and immediately reorganizes the 2D images with spatial
and temporal coherence so that images from the
same cardiac cycle are collated together to form a
single volume data set for that cardiac cycle
(Fig. 34.13). Many such volumes are produced during
a single sweep, and the actual number depends on
the duration of the sweep and the heart rate. The
images can be displayed as orthogonal multiplanar,
volume-rendered, or single-plane displays either as
cine loops or still images. The images can be gray
scale or color B mode, color Doppler, or a combination
of B mode and color Doppler with variable
translucency, the so-called glass-body display. The