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90
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
AP
Figure 2–84. Tomographic ultrasound image obtained on a normal fetal brain at 22 weeks’ gestation demonstrating successive coronal sections dis-
played from anterior (A) to posterior (P). The coronal planes correspond to the planes that are marked crossing the brain on the sagittal image. The slice
interval is 4.5 mm and the “marker dot” is seen in the midline on the cavum septi pellucidi.
2–85 , and 2–86 ). Usually a reference image is shown in the
upper left side of the picture, with the parallel lines representing the pertinent picture in a string of consecutive
sections displayed sequentially. The examiner can define
the distance between the slices usually ranging from 2 to 5
mm. The same display format can be applied to grayscale,
Doppler, or power Doppler containing volumes.
boxes are narrowed to a minimum; thus, the picture in
the rendering box represents the thick-slice image of
many collapsed 2D images ( Figure 2–87 ). It is useful to
study structures requiring better definition, such as the
vermis, the spine, and the lateral ventricles. This method
of obtaining the thick-slice display was lately replaced
by the one-step volume contrast imaging (VCI) display
mode 4D View (GE Healthcare).
Volume Rendering
Rendering displays includes a variety of modes. The most
commonly used are the surface and the inversion rendering modes. Advantages of the rendering modes include the
use of different lighting, filtering, and transparency levels,
which allows better visualization and perception of certain
structures.
Thick-Slice Rendering
In this mode, a number of successive slices are “collapsed”
into one single rendered 2D picture or plane, which
enhances edges, improves contrast detection, and gives
more depth to the image. If rendering boxes are placed
on the orthogonal planes, then on two of the planes the
Static Volume Contrast Imaging
This software application is essentially the same as the
thick-slice rendering, but instead of manipulating the
volume as described above using the thick-slice mode,
the same process is achieved by touching only one simple
control. By controlling the slice thickness to be between
2 and 5 mm, thus defining the number of tissue layers, US
artifacts, such as speckles and noise pixels, are decreased
so that anatomical edges are enhanced. This process results
in an image with improved tissue contrast
115
( Figures 2–88
and 2–89 ). Improved resolution and contrast using volume contrast imaging was compared to those of 2D US
images by different authors studying the posterior fossa.
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
RL
91
Figure 2–85.
from left to right. The sagittal planes correspond to the planes that are marked crossing the brain on the coronal image. The slice interval is 2.3 mm and
the marker dot is seen in the midline on the cavum septi pellucidi, therefore both right (R) and left (L) of the median sections are seen.
Tomographic ultrasound image obtained on a normal fetal brain at 22 weeks’ gestation showing successive sagittal sections displayed
B
BS
Figure 2–86.
from the bregma (B) to the base of the skull (BS). The axial planes correspond to the planes that are marked crossing the brain on the coronal image.
The slice interval is 3.7 mm and the “marker dot” is seen in the midline on the cavum septi pellucidi.
Tomographic ultrasound image obtained on a normal fetal brain at 22 weeks’ gestation demonstrating successive axial planes displayed
92
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
A
C
Figure 2–87.
C in the axial plane. The box or region of interest shows the selected area of the volume in all three planes that has been “collapsed” into a 2D image
enabling enhanced edge detection presented in box D as a “thick slice.” Note that the region of interest is placed at a level in which both lateral ventricles
are shown.
“The thick slice” mode is demonstrated. Box A shows a fetal brain at 22 weeks in the coronal plane, box B in the median plane, and box
The application of this filter improved the definition of the
landmarks of structures such as the cerebellar vermis and
fourth ventricle.
116
B
D
This is why surface rendering of the face and/or the skull
is so useful.
Radiograph, Maximum (“Bone”),
Surface Rendering
The image rendering of the fetal body surface is the most
widely known and most commonly used display modality of 3D. This mode allows reconstruction of surface
features of a given structure resembling a photograph
( Figure 2–90 ). The surface effect is achieved by various
directional illumination combinations. A selection of lighting, gradient, and opacity levels can enhance the clarity
and the desired quality of the surface-rendering effect. It is
important to understand that a significant amount of fluid
has to be between the transducer and the surface to be
or Transparency Mode
This mode allows selective imaging of the bony structures
by eliminating weaker echoes originating from the soft tissues of the fetus and prominently displaying strong echoes.
This results in a picture similar to a radiograph of the bony
structures of the fetus. Therefore, this mode is an ideal
tool in the demonstration of the cranial bones, as well as
the corresponding sutures
117 , 118
( Figure 2–1A ). This issue
was discussed earlier in this chapter. When searching for
anomalies of the skull or the fetal skeleton, this proves an
invaluable tool.
rendered. Because certain brain anomalies are associated
with facial dysmorphism, this image mode can be very
helpful in order to rule out or confirm anomalies involving
the face. In addition, the images provided can be of invaluable help for parents as well as for consulting physicians.
No detailed neurosonogram is complete without looking
at facial structures. This is even more important when
CNS anomalies are detected. Several anomalies of the
brain have been associated with pathognomonic features.
3D Sonoangiography
This mode enables selective imaging of blood vessels
after a 3D acquisition of power or color Doppler containing volume.
119 , 120
The technique of volume acquisition and manipulation is the same as with other 3D US
modes. This feature is often used to assess the cerebral
blood supply in normal and abnormal conditions. We are
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
93
A
B
C
A
A
B
C
B
Figure 2–88.
(b) just by touching one simple control (highlighted) and adjusting the desired slice thickness, in this case set at 2 mm. Note the difference in resolution and contrast of the images. On both images box A shows the coronal plane, box B shows the median plane, and box C shows the axial plane of the
fetal head.
Multiplanar display of the fetal brain in the three orthogonal planes before (a) and after applying the static volume contrast imaging
94
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
cc
tc
3v
qp
qc
4v
A
Figure 2–89. Sagittal view of the normal fetal head at 22 weeks of gestation. Comparison of two images obtained from the same ultrasound
volume, using a standard plane mode (a) and with static volume contrast imaging with a thickness of 3 mm (b). Note the difference in resolution
and contrast of the images, which allows better differentiation of different structures such as the corpus callosum (cc), tela choroidea (tc), quadrigeminal plate (qp), quadrigeminal cistern (qc), third ventricle (3v), fourth ventricle (4v), and vermis (v). The structures on (a) are identical to those
marked on (b).
mainly interested in the course of the pericallosal branch
of the anterior cerebral artery ( Figure 2–91 ), especially
in those cases in which agenesis of the corpus callosum
is suspected, as the presence of this artery is a useful
marker of at least partial callosal integrity. In other
cases, such as space-occupying lesions, the anatomy of
the vessels may be helpful in determining the size and
extent of the lesion. It is true that the course of any
main vessel in the brain can be obtained and followed
B
by regular 2D sonoangiography; however, it certainly
requires great skill and is sometimes impossible, whereas
3D US allows a median plane to be obtained quite easily
just by manipulating the volume and aligning the axial
and coronal planes in the right position. Furthermore,
a vascular tree of the whole brain corresponding to
the brain volume included in the region of interest is
displayed in a 3D fashion as a rendered image allowing
rotation using the three orthogonal planes and viewing
v
Figure 2–90.
resembling a photograph.
Surface rendering mode. Normal fetal face at 20 weeks (a) and at 32 weeks (b). Note how the nose and lips can be seen and recognized,
AB
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
cm
95
Leukostriate aa
fp
mca
Circle of Willis
pca
mca
aca
Figure 2–91. 3D angiography display mode enables selective imaging of blood flow through vessels after a 3D acquisition of a volume with power
Doppler. The anterior cerebral artery (acm), callosomarginal artery (cm), the pericallosal artery (p), orbitofrontal (of ), fronto polar artery (fp), middle
cerebral atery (mca), posterior cerebral artery (pca), and posterior communicating artery (Post Com) are presented.
of
p
aca
the course of the vessels from different angles. In addition, this image modality is an excellent teaching tool for
students and residents. For more details see Chapter 15.
Glass Body Mode
While color Doppler or power Doppler is switched on, it is
possible to simultaneously display grayscale and color flow
information. When the color rendering is used in conjunction with the transparency mode, a “glass body” mode is
achieved ( Figure 2–92 ).
A
Figure 2–92.
is used in conjunction with the color rendering, the “glass body” display
is achieved allowing us to see the brain vessels through the transparent
skull at 22 weeks (a). Volume data can also be displayed as color rendering
alone (b). The pericallosal artery and branches are demonstrated.
Glass body display mode. When a volume with grey scale
B
Inversion Mode
This display mode inverts the anechoic fluid-filled areas
of the acquired volume into echogenic structures. Thus,
the on-screen appearance is that of a castlike image of the
studied structure. This mode can be particularly useful
to display the ventricular system or any pathologic fluidfilled space of the fetal brain
39 , 121
( Figure 2–93 ). The use
of the inversion was demonstrated earlier in this chapter
when discussing sonoembryology. At that early stage
of fetal brain development, 3D US has made it possible
to visualize planes of the embryonic brain not available
in 2D US. Furthermore, the inversion rendering mode
allows volume estimation of embryonic brains
21 , 122
and
has been shown to be very helpful in understanding normal development of the fetal brain at these early stages by
displaying casts of the fluid-filled cavities.
40
Figures 2–18 ,
2–24 , 2–25 , 2–26 , 2–27 , 2–28 , and 2–29 show the use
of this display pertaining to the normal development
of the ventricular system. When using the inversion or
the surface-rendering mode, artifacts may result from
skull shadowing or from amniotic fluid; these can be
eliminated using the electronic scalpel during off-line
volume manipulation, as with any of the images obtained
by surface rendering. The electronic scalpel and the
eraser enable removal of structures that may obliterate or
96
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
R lateral ventricle
R
A
R
L
*
L lateral ventricle
L
*
B
Figure 2–93.
axial planes, of the right and left lateral ventricles are presented in images a and b, respectively. Inversion mode demonstrates the shape of both lateral
ventricles (arrows) and the cavum septi pellucidi (asterisk). Note the asymmetry of both ventricles depicted in both imaging modalities.
Multiplanar display of an ultrasound volume of a normal fetal brain at 21 weeks. The three orthogonal planes, coronal, sagittal, and
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
97
A
C
Figure 2–94. Measurement of fetal brain volume with 3D ultrasound. With the VOCAL mode, the internal borders of the head are traced manually
with stepwise rotation of 30 degrees, taking the skull base as the lower border. First the coronal plane was fixed as the anchor (box A), with the “marker
dot” on the midline. Second, the volume was determined by scrolling through the fetal head from one end to the other end and measuring the areas of
eight to ten serial coronal cuts. Third, the areas were calculated at the inner edge of the fetal skull bone by manual tracing. The VOCAL mode measures
the distance between each coronal cut and adds automatically the slices in between them to obtain the fetal brain volume. Box D shows the final volume
reconstruction of the total intracranial region using VOCAL.
obscure the object to be studied, improving evaluation of
the targeted object.
123
One of the most important advantages of using volume
scanning in general, more specifically, fetal neuroscanning,
is that all of the different displays and rendering modes can
be derived from the originally acquired volumes. In addition, any of the volumes displayed can be rotated around all
three orthogonal planes to achieve the right plane.
B
D
The VOCAL software (GE Healthcare, KretzTechnik) enables the ultrasonographer to trace onscreen stepwise rotating organs such as the brain and
to delineate or “cut out” their actual shapes. After doing
this, the volume of the “cut-out” organ can be measured,
and its content can be displayed using grayscale, glass
body, or angiography display modes ( Figure 2–94 ).
Volume measurements can be achieved using either
the multiplanar mode or the VOCAL software. If the
Volume Calculation: Virtual Organ
Computer-Aided Analysis (VOCAL)
The acquisition of a 3D volume allows the reconstruction
of a 2D image on which different, commonly used measurements can be performed. Among these are biparietal
diameter, head circumference, ventricular dimensions,
and different cerebellar measurements. However, the real
advantage over 2D images is its potential to calculate the
volume of a selected region of interest.
volume was acquired using color or power Doppler, the
vessel arrangement of the organ, as well as quantification of the blood flow containing voxels, can be counted
and displayed in a quantitative fashion. This is one of
the display modes toward which a significant amount
of research activity is directed to evaluate its potential
clinical use. Good intra- and interobserver reproducibility of intracranial volume calculation has been reported,
as well as a good correlation with biparietal diameter (BPD) and head circumference (HC), by different
98
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
A
Left and right lateral processes
Left
Vertebral body
CD
Figure 2–95. Multiplanar mode and maximum or x-ray display of the fetal spine and ribs at 20 weeks’ gestation. This mode allows simultaneous
visualization of the three orthogonal planes of the spine and evaluation of the three ossification centers, the lateral processes, and the bodies of the
vertebrae. Axial plane in box A, sagittal plane in box B, and coronal plane in box C. Note that the ribs are not demonstrated in box C, but their shadow
is visible, since the marker dot is placed on the body of the vertebrae anterior to the level of the ribs. The maximum mode was applied to obtain the
rendered image as demonstrated in box D, which allows the identification of the 12
ously (arrowheads).
Right
B
th
Right lateral processes
Vertebral body
12th ribs
ribs and visualization of the three ossification centers simultane-
authors, making it available for research and eventually
for clinical use.
124 – 126
THE FETAL SPINE
Because the spinal cord is part of the CNS and is found
within the vertebral canal, it is imperative to evaluate the
bony casing of the spinal cord. When evaluating the spine,
3D US appears to be an important adjunct to 2D imaging
in arriving at the correct diagnosis when an abnormality
is suspected.
Technique
The choice of which transducer to use to obtain the volume will depend upon the orientation of the spine and
its size. As gestation advances, the best way to obtain 3D
images of the fetal column is by using the transabdominal
US probe. With regards to the plane of acquisition, the best
results are obtained by using the sagittal view. It is important to adjust the angle of rotation in order to include the
ribs in the volume. Once the volume is acquired, the next
step is to rotate the spine to obtain perfect sagittal and
coronal planes.
The 3D volume can be evaluated using multiplanar display, volume rendering with the maximum-intensity mode,
or a combination of both methods. The major advantage
of the use of 3D when evaluating the fetal spine is that
this image modality allows simultaneous visualization of
the three ossification centers, the lateral processes, and
the vertebral bodies of each vertebra
2–96 , and 2–97 ). This allows a better understanding of the
complex anatomy of the spine compared with 2D US.
127 – 130
( Figures 2–95 ,
132 , 133
An additional advantage is the possibility of rotating the
volume around all three orthogonal planes and visualizing
the spine from different angles.
129–132
Furthermore, in the cases of neural tube defects, 3D US
has been shown to be useful in determining the level and
extent of the lesion.
127,128,133–135
This can be easily achieved
by using the maximum mode in a thin slice, which allows
the identification of the 12th rib; thus, the vertebral segments can be counted starting with the one connected to
the last identifiable rib ( Figure 2–95 ). However, 3D rendering of the spine may sometimes be inconclusive, especially
in cases of small and low defects, as pointed out in a recent
review of 3D US examination of the fetal CNS. The authors
stated that a normal 3D image of the bony elements of the
spine is not reassuring with regard to the presence of spina
136
bifida.
Other applications of 3D US have included the mea-
surement of the size and volume of the thoracolumbar
137
the spinal length,
spine,
nal canal,
139
with no clinical use suggested. At times, the
138
and the size of the lumbar spi-
surface-rendering mode may be used to demonstrate the
cutaneous surface of the spine, which might be clinically
useful when evaluating an open spina bifida.
Chapter 2 Normal Two- and Three-Dimensional Neurosonography of the Prenatal Brain
a
99
Left
Lateral processes
Right
Lateral processes
Vertebral bodies
A
Posterior
Anterior
Lateral
processess
Vertebral
bodies
B
Figure 2–96.
views displayed from posterior to anterior. The body of the vertebrae and the lateral processes from different angles are viewed. Note how the contents
of the neural canal are demonstrated in the central image of the sagittal sequence (arrow).
Tomographic ultrasound images obtained on a normal fetal spine at 24 weeks. (A) Sagittal views displayed from left to right. (B) Coronal
Figure 2–97. Rendering image obtained on a normal spine at 20 weeks.
Note that depending on the gestational age of the fetus, visualization of
the entire spine in a single image can be presented.
REFERENCES
1. Kossoff G. Griffith KA, Dixon CE. Is the quality of transvaginal
images superior to transabdominal ones under matched conditions?
Ultrasound Obstet Gynecol. 1991;1:29–35.
2. Kossoff G, Garret WJ, Radavaniovich G. Ultrasonic atlas normal
brain of infant. Ultrasound Med Biol. 1974;1:259–266.
3. Garret WJ, Kossoff G, Jones RF. Ultrasonic cross-sectional visualization of hydrocephalus in infants. Neuroradiology. 1975;8:279–288.
4. Lees RF, Harrison RB, Sims TL. Gray scale ultrasonography in the
evaluation of hydrocephalus and associated abnormalities in infants.
Am J Dis Child. 1978;132:376–378.
5. Babcock DS, Han BK, LeQuesne GW. B-mode gray scale ultrasound of the head in the newborn and young infant. AJR. 1980;134:
457–468.
6. Skolnick ML, Rosenbaum AE, Matzuk T, et al. Detection of dilated
cerebral ventricle in infants: A correlative study between ultrasound
and computed tomography. Radiology. 1979;131:447–451.
7. Haber K, Wachter RD, Christenson PC, et al. Ultrasonic evaluation
of intracranial pathology in infants: A new technique. Radiology.
1980;134:173–178.
8. Vlieger M. Evaluations of echoencephalography. J Clin Ultrasound.
1980;8:38.
9. Johnson ML, Rumack CM. Ultrasonic evaluation of the neonatal
brain. Radiol Clin North Am. 1980;18:117–131.
10. Ben-Ora A. Eddy L, Hatch G, et al. The anterior fontanelle as
an acoustic window to the neonatal ventricular system. J Clin
Ultrasound. 1980;8:65–67.
11. Dewbury KC, Aluwihare APR. The anterior fontanelle as an ultrasound window for study of the brain: A preliminary report. Br J
Radiol. 1980;53:81–84.