This document provides guidelines for performing obstetric ultrasound examinations at various stages of pregnancy. It discusses indications, imaging parameters, and documentation requirements for first trimester, standard second/third trimester, limited, and specialized ultrasound exams. Key aspects include evaluating gestational sac features in the first trimester, assessing fetal anatomy and biometric measurements in later exams, and documenting important findings such as placental location and amniotic fluid levels. Adherence to these guidelines helps maximize detection of fetal abnormalities.
2. introduction
This course is an educational tool
designed to assist practitioners in
providing appropriate diagnostic
knowledge to care for patients.
The practice of medicine involves not
only the science, but also the art of
dealing with the prevention,
diagnosis,alleviation, and treatment of
disease.
3. The variety and complexity of
human conditions make it
impossible to always reach the
most appropriate diagnosis or to
predict with certainty a particular
response to treatment.
Therefore, it should be recognized
that adherence to these practice
parameters will not assure an
accurate diagnosis or a successful
outcome.
4. All that should be expected is
that the practitioner will
follow a reasonable course of
action based on current
knowledge, available
resources, and the needs of
the patient to deliver effective
5. The clinical aspects contained in specific
sections of this practice parameter
(Introduction, Classification of Fetal
Sonographic Examinations, Specifications
of the Examination, Equipment
Specifications, and Fetal Safety) were
revised collaboratively by the American
College of Radiology (ACR), the American
Institute of Ultrasound in Medicine
(AIUM), the American College of
Obstetricians and Gynecologists (ACOG),
and the Society of Radiologists in
Ultrasound (SRU).
6. Recommendations for
physician qualifications,
written request for the
examination, procedure
documentation, and quality
control vary among the
organizations and are
addressed by each separately.
This practice parameter has
been developed for use by
practitioners performing
obstetrical sonographic studies.
7. Fetal ultrasound should be
performed only when there is a valid
medical reason, and the lowest
possible ultrasonic exposure settings
should be used to gain the necessary
diagnostic information .A limited
examination may be performed in
clinical emergencies or for a limited
purpose such as evaluation of fetal or
embryonic cardiac activity, fetal
position, or amniotic fluid volume.
8. A limited follow-up examination may be
appropriate for re-evaluation of fetal size or
interval growth or to re-evaluate
abnormalities previously noted if a
complete prior examination is on record.
While this practice parameter describes the
key elements of standard sonographic
examinations in the first trimester and
second and third trimesters, a more detailed
anatomic examination of the fetus may be
necessary in some cases, such as when an
abnormality is found or suspected on the
standard examination or in pregnancies at
high risk for fetal anomalies.
9. In some cases, other specialized
examinations may be necessary as
well.
While it is not possible to detect
all structural congenital anomalies
with diagnostic ultrasound,
adherence to the
following practice parameters will
maximize the possibility of
detecting many fetal
abnormalities.
11. A. First Trimester
Ultrasound Examination
A standard obstetrical sonogram in the first trimester
includes evaluation of the presence, size, location, and
number of gestational sac(s). The gestational sac is
examined for the presence of yolk sac and embryo/fetus.
When an embryo/fetus is detected, it should be measured
and cardiac activity recorded by 2D video clip or Mmode.
Use of spectral Doppler is discouraged. The uterus, cervix,
adnexa, and culde sac region should be
examined.
12. A standard obstetrical sonogram in the second
or third trimester includes an evaluation of
fetal presentation, amniotic fluid volume,
cardiac activity, placental position, fetal
biometry, and fetal number, plus an anatomic
survey. The maternal cervix and adnexa should
be examined as clinically appropriate when
technically feasible.
B. Standard Second or Third
Trimester Examination
13. A limited examination is performed when a
specific question requires investigation. For
example, in most routine nonemergency cases a
limited examination could be performed to
confirm fetal heart activity in a bleeding patient,
or to verify fetal presentation in a laboring
patient. In most cases limited sonographic
examinations are appropriate only when a prior
complete examination is on record.
C. Limited Examination
14. A detailed anatomic examination is performed
when an anomaly is suspected on the basis of
history, biochemical abnormalities, or the
results of either the limited or standard scan.
Other specialized examinations might include
fetal Doppler ultrasound, biophysical profile,
fetal echocardiogram, or additional biometric
measurements.
D. Specialized Examinations
15. WRITTEN REQUEST FOR
THE EXAMINATION
The written or electronic request for an
obstetrical ultrasound examination should
provide sufficient information to demonstrate
the medical necessity of the examination and
allow for its proper performance and
interpretation.
Documentation that satisfies medical necessity
includes 1) signs and symptoms and/or 2)
16. WRITTEN REQUEST FOR
THE EXAMINATION
relevant history (including known diagnoses). Additional
information regarding the specific reason for the examination
or a provisional diagnosis would be helpful and may at times
be needed to allow for the proper performance and
interpretation of the examination. The request for the
examination must be originated by a physician or other
appropriately licensed health care provider. The accompanying
clinical information should be provided by a physician or other
appropriately licensed health care provider familiar with the
patient’s clinical problem or question and consistent with the
state’s scope of practice requirements
18. A. First Trimester
Ultrasound Examination
1. Indications
Indications for first trimester3 sonography include:
a. Confirmation of the presence of an intrauterine pregnancy .
b Evaluation of a suspected ectopic pregnancy .
c. Defining the cause of vaginal bleeding.
d. Evaluation of pelvic pain.
e. Estimation of gestational (menstrual4) age.
f. Diagnosis or evaluation of multiple gestations.
g. Confirmation of cardiac activity.
19. A. First Trimester
Ultrasound Examination
1. Indications
Indications for first trimester3 sonography include:
h. Imaging as an adjunct to chorionic villus sampling, embryo transfer, and
localization and removal of
an intrauterine device (IUD).
i. Assessing for certain fetal anomalies, such as anencephaly, in high risk patients.
j. Evaluation of maternal pelvic masses and/or uterine abnormalities.
k. Measuring the nuchal translucency (NT) when part of a screening program for
fetal aneuploidy.
l. Evaluation of suspected hydatidiform mole
20. A. First Trimester
Ultrasound Examination
Scanning in the first trimester may be
performed either transabdominally
or transvaginally.
If a transabdominal examination is
not definitive, a transvaginal scan or
transperineal scan should be
performed whenever possible
2. Imaging
parameters
21. A. First Trimester
Ultrasound Examination
a. The uterus, (including the cervix),
and adnexa should be evaluated for the
presence of a gestational
sac. If a gestational sac is seen, its
location should be documented. The
gestational sac should be
evaluated for the presence or absence
of a yolk sac or embryo, and the crown-
rump length should be
recorded, when possible
22. A definitive diagnosis of intrauterine pregnancy can be
made when an intrauterine gestational sac
containing a yolk sac or embryo/fetus with cardiac activity is
visualized. A small, eccentric intrauterine fluid collection
with an echogenic rim can be seen before the yolk sac and
embryo are detectable in a very early intrauterine
pregnancy. In the absence of sonographic signs of ectopic
pregnancy, the fluid collection is highly likely to represent an
intrauterine gestational sac. In this circumstance, the
intradecidual sign may be helpful.
a. The uterus
23. Follow-up sonography and/or serial determination of maternal serum
HCG (human chorionic gonadotropin) levels are appropriate in
pregnancies of undetermined location to avoid inappropriate intervention
in a potentially viable early pregnancy.
The crown-rump length is a more accurate indicator of gestational
(menstrual) age than is mean gestational sac diameter. However, the
mean gestational sac diameter may be recorded when an embryo is not
identified.
Caution should be used in making the presumptive diagnosis of a
gestational sac in the absence of a
definite embryo or yolk sac. Without these findings an intrauterine fluid
collection could represent a pseudo-gestational sac associated with an
ectopic pregnancy
a. The uterus
24. b. Presence or absence of cardiac
activity should be documented with 2D
video clip or M-mode.
With transvaginal scans, while cardiac
motion is usually observed when the
embryo is 2 mm or greater in length, if an
embryo less than 7 mm in length is seen
without cardiac activity, a subsequent
scan in one week is recommended to
ensure that the pregnancy is nonviable
25. c. Fetal number should be
documented.
Amnionicity and
chorionicity should be
documented for all multiple
gestations when possible.
26. d. Embryonic/fetal anatomy appropriate
for the first trimester should be assessed.
For those patients desiring to assess their
individual risk of fetal aneuploidy, a very
specific measurement of the NT during a
specific age interval is necessary (as
determined by the laboratory used). See the
guidelines for this measurement below.
e. The nuchal region should be imaged, and
abnormalities such as cystic hygroma should be
documented.
27. NT measurements should be used (in conjunction
with serum biochemistry) to determine the risk for
having a fetus with aneuploidy or other anatomical
abnormalities such as heart defects.
In this setting, it is important that the practitioner
measure the NT according to established guidelines
for measurement. A quality assessment program is
recommended to ensure that false-positive and
false-negative results are kept to a minimum
e. The nuchal region should be imaged, and
abnormalities such as cystic hygroma should be
documented.
28. i. The margins of the NT edges must be clear
enough for proper placement of the calipers.
ii. The fetus must be in the midsagittal plane.
iii. The image must be magnified so that it is
filled by the fetal head, neck, and upper
thorax.
Guidelines for NT measurement:
29. iv. The fetal neck must be in a neutral
position – not flexed and not
hyperextended.
v. The amnion must be seen as separate
from the NT line.
vi. The (+) calipers on the ultrasound must
be used to perform the NT measurement.
Guidelines for NT measurement:
30. vii. Electronic calipers must be placed on
the inner borders of the nuchal line with
none of the horizontal crossbar itself
protruding into the space.
viii. The calipers must be placed
perpendicular to the long axis of the
fetus.
Guidelines for NT measurement:
34. Topics:
Definition of Nuchal Translucency
Measurement Criteria NT in Trisomy 21
Screening Advantages/Limitations of NT
Screening Differential Diagnosis of Increased NT
Mechanisms of Increased NT Fetal Anomalies associated with Increased NT
Follow-up on Our Patients
58. f. The uterus including the cervix,
adnexal structures, and cul-de-sac
Abnormalities should be imaged and
documented.The presence, location, appearance,
and size of adnexal masses should be documented.
The presence and number of leiomyomata should
be documented. The measurements of the largest
or any potentially clinically significant leiomyomata
should be documented. The cul-de-sac should be
evaluated for the presence or absence of fluid.
Uterine anomalies should be documented.
59. Indications for second and third trimester sonography include, but are not limited to:
a. Screening for fetal anomalies .
b. Evaluation of fetal anatomy.
c. Estimation of gestational (menstrual) age.
d. Evaluation of fetal growth.
e. Evaluation of vaginal bleeding.
f. Evaluation of abdominal or pelvic pain.
g. Evaluation of cervical insufficiency.
h. Determination of fetal presentation.
i. Evaluation of suspected multiple gestation.
j. Adjunct to amniocentesis or other procedure.
k. Evaluation of significant discrepancy between uterine size and clinical dates.
l. Evaluation of pelvic mass.
B. Second and Third Trimester
Ultrasound Examination
1. Indications
60. Indications for second and third trimester sonography include, but are not limited to:
m. Evaluation of suspected hydatidiform mole.
n. Adjunct to cervical cerclage placement.
o. Suspected ectopic pregnancy.
p. Suspected fetal death.
q. Suspected uterine abnormality.
r. Evaluation of fetal well-being.
s. Suspected amniotic fluid abnormalities.
t. Suspected placental abruption.
u. Adjunct to external cephalic version.
v. Evaluation of premature rupture of membranes and/or premature labor.
w. Evaluation of abnormal biochemical markers.
x. Follow-up evaluation of a fetal anomaly.
y. Follow-up evaluation of placental location for suspected placenta previa.
z. History of previous congenital anomaly.
B. Second and Third Trimester
Ultrasound Examination
1. Indications
61. Abnormal heart rate and/or rhythm should be
documented. Multiple gestations require the
documentation of additional information:
chorionicity, amnionicity,comparison of fetal
sizes, estimation of amniotic fluid volume
(increased, decreased, or normal) in each
gestational sac, and fetal genitalia (when
visualized).
B. Second and Third Trimester
Ultrasound Examination
a. Fetal cardiac activity, fetal number, and presentation should be documented.
62. Although it is acceptable for experienced
examiners to qualitatively estimate
amniotic fluid volume, semi quantitative
methods have also been described for this
purpose (e.g., amniotic fluid index, single
deepest pocket, two-diameter pocket)
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
b. A qualitative or semi quantitative estimate of amniotic fluid volume should be
documented.
63. The umbilical cord should be imaged, and the number of vessels in the cord documented. The
placental cord insertion site .should be documented when technically possible .
It is recognized that apparent placental position early in pregnancy may not correlate well with its
location at the time of delivery.
Transabdominal, transperineal, or transvaginal views may be helpful in visualizing the internal
cervical os and its relationship to the placenta.
Transvaginal or transperineal ultrasound may be considered if the cervix appears shortened or cannot
be adequately visualized during the transabdominal sonogram [29,30].
A velamentous (also called membranous) placental cord insertion that crosses the internal os of the
cervix is vasa previa, a condition that has a high risk of fetal mortality if not diagnosed prior to labor
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
c. The placental location, appearance, and relationship to the internal cervical os
should be documented.
64. First-trimester crown-rump measurement is the most accurate
means for sonographic dating of pregnancy. Beyond this period, a
variety of sonographic parameters such as biparietal diameter,
abdominal circumference, and femoral diaphysis length can be
used to estimate gestational (menstrual) age. The variability of
gestational (menstrual) age estimation, however, increases with
advancing pregnancy. Significant discrepancies between
gestational (menstrual) age and fetal measurements may suggest
the possibility of fetal growth abnormality, intrauterine growth
restriction, or macrosomia
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
d. Gestational (menstrual) age assessment
65. The pregnancy should not be redated after an accurate
earlier scan has been performed and is
available for comparison.
i. Biparietal diameter is measured at the level of the
thalami and cavum septi pellucidi or columns of the fornix.
The cerebellar hemispheres should not be visible in this
scanning plane. The measurement is taken from the outer
edge of the proximal skull to the inner edge of the distal
skull.
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
d. Gestational (menstrual) age assessment
66. The head shape may be flattened (dolichocephaly) or
rounded (brachycephaly) as a normal variant. Under these
circumstances, certain variants of normal fetal head
development may make measurement of the head
circumference more reliable than biparietal diameter for
estimating gestational (menstrual) age.
ii. Head circumference is measured at the same level as the
biparietal diameter, around the outer perimeter of the
calvarium. This measurement is not affected by head shape.
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
d. Gestational (menstrual) age assessment
67. iii. Femoral diaphysis length can be reliably used after 14 weeks
gestational (menstrual) age. The long axis of the femoral shaft is
most accurately measured with the beam of insonation being
perpendicular to the shaft, excluding the distal femoral epiphysis.
iv. Abdominal circumference or average abdominal diameter
should be determined at the skin line on a true transverse view at
the level of the junction of the umbilical vein, portal sinus, and
fetal stomach when visible. Abdominal circumference or average
abdominal diameter measurement is used with other biometric
parameters to estimate fetal weight and may allow detection of
intrauterine growth restriction or macrosomia.
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
d. Gestational (menstrual) age assessment
68. Fetal weight can be estimated by obtaining
measurements such as the biparietal diameter, head
circumference, abdominal circumference or average
abdominal diameter, and femoral diaphysis
length. Results from various prediction models can
be compared to fetal weight percentiles from
published nomograms
B. Second and Third Trimester
Ultrasound Examination
e. Fetal weight estimation
69. If previous studies have been performed,
appropriateness of growth should also be
documented.
Scans for growth evaluation can typically be
performed at least 2 to 4 weeks apart. A shorter
scan interval may result in confusion as to whether
measurement changes are truly due to growth as
opposed to variations in the technique itself.
B. Second and Third Trimester
Ultrasound Examination
e. Fetal weight estimation
70. Currently, even the best fetal weight prediction
methods can yield errors as high as ±15
percent. This variability can be influenced by
factors such as the nature of the patient
population, the number and types of anatomic
parameters being measured, technical factors
that affect the resolution of ultrasound images,
and the weight range being studied.
B. Second and Third Trimester
Ultrasound Examination
e. Fetal weight estimation
71. Evaluation of the uterus, adnexal structures, and cervix should
be performed when appropriate. If the cervix cannot be
visualized, a transperineal or transvaginal scan may be
considered when evaluation of the cervix is needed.This will
allow recognition of incidental findings of potential clinical
significance. The presence,location, and size of adnexal masses
and the presence of at least the largest and potentially clinically
significant leiomyomata should be documented. It is not always
possible to image the normal maternal ovaries during the
second and third trimesters.
B. Second and Third Trimester
Ultrasound Examination
f. Maternal anatomy
72. • g. Fetal anatomic survey
• Fetal anatomy, as described in this document, may be adequately assessed
by ultrasound after
• approximately 18 weeks gestational (menstrual) age. It may be possible to
document normal
• structures before this time, although some structures can be difficult to
visualize due to fetal size,
• position, movement, abdominal scars, and increased maternal abdominal
wall thickness [39]. A
• second or third trimester scan may pose technical limitations for an
anatomic evaluation due to
• imaging artifacts from acoustic shadowing. When this occurs, the report of
the sonographic
• examination should document the nature of this technical limitation. A
follow-up examination may be
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
73. • g. Fetal anatomic survey
• The following areas of assessment represent the minimal elements of a standard examination of
fetal
• anatomy. A more detailed fetal anatomic examination may be necessary if an abnormality or
• suspected abnormality is found on the standard examination.
• i. Head, face, and neck
• Lateral cerebral ventricles
• Choroid plexus
• Midline falx
• Cavum septi pellucidi
• Cerebellum
• Cistern magna
• Upper lip
• Comment
• A measurement of the nuchal fold may be helpful during a specific age interval to assess the risk of
• aneuploidy
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
74. • g. Fetal anatomic survey
• The following areas of assessment represent the minimal elements
of a standard examination of fetal
• anatomy. A more detailed fetal anatomic examination may be
necessary if an abnormality or
• suspected abnormality is found on the standard examination.
• iv. Spine
• Cervical, thoracic, lumbar, and sacral spine
• v. Extremities
• Legs and arms
• vi. Gender
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
75. • g. Fetal anatomic survey
• The following areas of assessment represent the minimal elements of a standard examination of
fetal
• anatomy. A more detailed fetal anatomic examination may be necessary if an abnormality or
• suspected abnormality is found on the standard examination.
• ii. Chest
• Heart [41-43]
• Four-chamber view
• Left ventricular outflow tract
• Right ventricular outflow tract
• iii. Abdomen
• Stomach (presence, size, and situs)
• Kidneys
• Urinary bladder
• Umbilical cord insertion site into the fetal abdomen
2. Imaging
parameters
B. Second and Third Trimester
Ultrasound Examination
76. REFERENCES
1. Barnett SB, Ter Haar GR, Ziskin MC, Rott HD, Duck FA, Maeda K. International recommendations and
guidelines for the safe use of diagnostic ultrasound in medicine. Ultrasound Med Biol 2000;26:355-366.
2. Bly S, Van den Hof MC. Obstetric ultrasound biological effects and safety. J Obstet Gynaecol Can
2005;27:572-580.
3. Barnhart K, van Mello NM, Bourne T, et al. Pregnancy of unknown location: a consensus statement of
nomenclature, definitions, and outcome. Fertil Steril 2011;95:857-866.
4. Jeve Y, Rana R, Bhide A, Thangaratinam S. Accuracy of first-trimester ultrasound in the diagnosis of early
embryonic demise: a systematic review. Ultrasound Obstet Gynecol 2011;38:489-496.
5. Thilaganathan B. The evidence base for miscarriage diagnosis: better late than never. Ultrasound Obstet
Gynecol 2011;38:487-488.
6. Chambers SE, Muir BB, Haddad NG. Ultrasound evaluation of ectopic pregnancy including correlation with
human chorionic gonadotrophin levels. Br J Radiol 1990;63:246-250.
7. Hill LM, Kislak S, Martin JG. Transvaginal sonographic detection of the pseudogestational sac associated
with ectopic pregnancy. Obstet Gynecol 1990;75:986-988.
8. Kirk E, Daemen A, Papageorghiou AT, et al. Why are some ectopic pregnancies characterized as pregnancies
of unknown location at the initial transvaginal ultrasound examination? Acta .
78. Three-dimensional Ultrasound Imaging
Three-dimensional ultrasound (3DUS) has become an
increasingly important component of clinical imaging.
While early applications have been focused on cardiac,
obstetric, and gynecologic applications its capabilities
continue to expand throughout the clinical arena. This
expansion is driven by important improvements in
technology, image quality and clinical ease of use. This
chapter will provide a brief review of the technology
behind 3D and 4D ultrasound imaging, clinical
considerations in acquiring, displaying and analyzing
3D/4D ultrasound data and the clinical contributions
this exciting technology is making.
79. • Ultrasound is a versatile imaging technique that can reveal
• the internal structure of organs, often with astounding
clarity.
• Ultrasound is unique in its ability to image patient anatomy
• and physiology in real time, providing an important, rapid
• and noninvasive means of evaluation. Ultrasound continues
to
• make significant contributions to patient care by reassuring
• patients and enhancing their quality of life by helping
physicians
• understand their anatomy in ways not possible with other
• techniques.
80. • Three-dimensional ultrasound (3DUS) is an increasingly
• important area of ultrasound development [1]. 3DUS
exploits
• the real-time capability of ultrasound to build a volume
that
• can then be explored using increasingly affordable
highperformance
• workstations. 3DUS is a logical evolution of
• ultrasound technology and complements other parallel
developments
• underway at this time, including harmonic imaging
• and the development of ultrasound contrast materials.
81. • The continued clinical acceptance of 3DUS depends on
• three broad areas: these are volumetric data acquisition, volume
• data analysis and volume display. The particular strategy
• chosen by a vendor significantly shapes the scanner performance
• and resultant clinical versatility. A fourth consideration
• underlies the others, but ultimately will play a significant role
• affecting the clinical acceptance of the 3DUS. That is, the
• performance of 3DUS scanning systems must meet or exceed
• that of current 2DUS imaging systems with respect to image
• quality, features and interactivity.
• This paper will provide a brief review of the technology
• behind 3D and 4D ultrasound imaging, clinical considerations
• in acquiring, displaying and analyzing 3D/4D ultrasound data
• and the clinical contributions this exciting technology is making.
82. • II. EQUIPMENT DESIGN
• Design of clinically useful scanning equipment is crucially
• dependent on having an easy-to-use system that provides rapid
• feedback to the clinician user in a straightforward manner.
• While superb image quality is expected, it also is important
• to avoid an overabundance of bells and whistles that often
• distract and overwhelm users rather than enhance the clinical
• imaging experience. Fundamental to an optimal operational
• environment is a highly functional, ergonomically designed
• user interface (Fig. 1). Selection of scanner features should
• be task related, obvious and context dependent.
84. • Most modern
• scanners provide the capability to acquire a variety of
ultrasound
• data types (Fig. 2). Data display and analysis integral
• to the scanner should provide interactive functionality with
an
• intuitive user interface. Scanner operation should
seamlessly
• transition between acquiring data, displaying the results
and
• saving or sending to a Picture Archiving Communications
• System (PACS).
86. III. PURCHASE CONSIDERATIONS
• Decisions regarding purchase of a particular piece of ultrasound
• equipment often are driven from a variety of considerations.
• From a practical point of view there are several considerations
• in selecting clinical scanning system. Fundamentally, it
• is important to consider the clinical application and need(s)
• to be met. It is important to understand the operational
• requirements for each type of clinical study to obtain good
• clinical results. Evaluation of the skill level required to obtain
• diagnostic information for each type of study is essential. A
• review of the scanner features essential to obtain sufficient
• information to accomplish the clinical scanning is required.
87. • It is important to maintain focus on the key features and not
• get overwhelmed by the flashy (and often expensive) unneeded
• features that might be available. Since clinical needs will grow
• over time it is important to determine if there is an upgrade
• pathway for future growth or expansion of scanner capability.
• Finally, an important consideration in purchase of any complex
• imaging equipment is to make sure that there will be adequate
• applications training at purchase and later on as needed.
88. • If the scanner will be used for 3DUS applications then it is
• important to know what 3D/4D applications are most likely
• to be performed. Fetal heart scanning is more demanding
• than imaging the abdomen. Also, identification of whether
• multi-planar slices will be adequate or if rendering also will
• be necessary. If measurements are a part of the examination
• determine the type and complexity of the measurements needs
• to be known. For example, length and area are less challenging
• than a complete segmentation of a complex cystic structure.
• Finally, determine if advanced imaging capabilities be available
• in the 3DUS imaging modes. Often these capabilities are
• part of the scanner but not available for 3D imaging.
89. IV. ACQUISITION APPROACHES
• Acquisition of a data volume requires significant computing
• resources to process the acoustic and position data rapidly
and
• create a volume. Various strategies are available in clinical
• scanners with most directed toward providing ”real-time”
• images to the clinical user.
• Among the primary approaches employed are free-hand
• scanning with and without position sensing, mechanical
devices
• integrated into the transducer and matrix array technology
• (Fig. 3).
91. • Mechanical devices may be integral within
• the scan head or external fixtures. Two-dimensional matrix
• array transducers promise to make real-time volume
imaging
• a reality at the patients bedside in the near future.
• Fundamental limitations in the speed of sound and the
• number of scan lines required to acquire a complete
volume
• of data often impose tradeoffs between line density, frame
• rate and depth of field that can compromise data resolution
• (Fig. 4).
93. • Good interpolation algorithms can mitigate
some of Similarly, due to the anisotropic
resolution of most transducers
• used for 3DUS acquisition there is generally an
optimal
• orientation for the volume acquisition (Fig. 5).
95. V. DISPLAY STRATEGIES
• Visualization of the relevant patient anatomy will ultimately
• determine the clinical utility of 3DUS. Although traditional
• methods of viewing multi-planar images provide much
information,
• volume rendering for visualization of underlying
•
• patient anatomy including blood flow offers new ways to
• visualize complex anatomy in a single image and to
enhance
• the visibility of structures that previously were difficult to
• appreciate.
96. • Visualization depends on optimised algorithms to display
• the structure of interest and fast computing hardware to display
• the results fast enough to interactively adjust parameters or
• viewing orientation. Volume data currently are displayed using
• two primary methods: these are a series of multi- planar images
• (typically three slices that are orthogonal to each other),
• and rendered images that show entire structures throughout the
• volume (Fig. 6).
98. • VII. CLINICAL APPLICATIONS
• Ongoing clinical research is evaluating clinical applications
• likely to have the greatest clinical impact on patient diagnosis
• and management. Several areas of 3DUS have emerged that
• offer advantages compared to 2DUS. A few examples will
• illustrate some areas in which clinical management improvements
• have been achieved.
• To date, fetal, cardiac and gynecological areas have received
• the most attention (Fig. 10), with other clinical areas receiving
• increasing interest including imaging of vascular anatomy,
• prostate volume measurement and assessment of seed placement,
• guidance of interventional needles and catheters, neonatal
• head evaluation, and evaluation of breast mass vascularity.
• Fig.
100. • In the fetus, improved visualization of fetal features, including
• the face and limbs, has improved anomaly identification
• and been immediately appealing for clearly sharing development
• information with the family.
• Cardiac applications have provided a surgeon’s eye view
• using transesophageal and transthoracic techniques to assess
• valve geometry and motion and to plan operative procedures.
• Fetal cardiac imaging has become an increasingly important
• part of prenatal diagnosis as a result of the development of
• four-dimensional imaging methods [3], [4]
• Gynecological applications include evaluating congenital
• anomalies of the uterus, endometrial cancer, adnexal masses,
• intrauterine device position and follicular cysts. With 3DUS, it
• is possible to obtain the coronal plane of the uterus (Fig. 11),
• which is not possible with 2DUS. This view greatly facilitates
• identification of uterine anatomy, which can be important in
• managing infertility and congenital anomalies
102. REFERENCES
• [1] Nelson TR, Downey DB, Pretorius DH, Fenster A. Three-dimensional
• Ultrasound. New York: Lippincott, 1990.
• [2] Riccabona M, Nelson TR, Pretorius DH, Davidson TE. Threedimensional
• sonographic measurement of bladder volume. J Ultrasound
• Med 1996;15:627-632.
• [3] Nelson TR, Pretorius DH, Sklansky M, Hagen-Ansert S., Threedimensional
• echocardiographic evaluation of fetal heart anatomy
• and function: acquisition, analysis, and display, J Ultrasound Med.
• 1996,15(1):1-9
• [4] Goncalves LF, Lee W, Chaiworapongsa T, Espinoza J, Schoen ML,
• Falkensammer P, Treadwell M, Romero R., Four-dimensional ultrasonography
• of the fetal heart with spatiotemporal image correlation.,
• Am J Obstet Gynecol. 2003, 189(6):1792-802.
• [5] Jurkovic D, Geipel A, Gruboeck K, et al. Three-dimensional ultrasound
• for the assessment of uterine anatomy and detection of congenital
• anomalies: A comparison with hysterosalpingography and twodimensional
• sonography. Ultrasound Obstet Gynecol 1995;5:233-237.
• [6] Merz E, Bahlmann F, Weber G. Volume scanning in the evaluation of
• fetal malformations: A new dimension in prenatal diagnosis. Ultrasound
• Obstet Gynecol 1995;5:222-227.
• [7] Rose SC, Pretorius DH, Kinney TB, et al. 3D sonographic guidance
• of transvenous intrahepatic invasive procedures: Feasibility of a new
• technique. J Vasc Intervent Radiol 1999;10:189-198.
• [8] Downey DB, Fenster A. Three-dimensional ultrasound: A maturing
• technology. Ultrasound Quart 1998;14:25-40.
128. 3D scans show still
pictures of your baby in
three dimensions. 4D
scans show moving 3D
images of your baby,
with time being the
fourth dimension.
It's natural to be really
excited by the prospect
of your first scan. But
some mums find the
standard 2D scans
disappointing when all
they see is a grey, blurry
outline. This is because
the scan sees right
through your baby, so
the photos show her
internal organs.
129. With 3D and 4D scans, you see
your baby's skin rather than her
insides. You may see the shape
of your baby's mouth and nose,
or be able to spot her yawning
or sticking her tongue out.
130. -3D and 4D scans are considered as safe as 2D
scans, because the images are made up of
sections of two-dimensional images converted
into a picture. However, experts do not
recommend having 3D or 4D scans purely for a
souvenir photo or recording, because it means
that you are exposing your baby to more
ultrasound than is medically necessary. Some
private ultrasounds can be as long as 45
minutes to an hour, which may be longer than
recommended safety limits.
131. 3D and 4D scans may nonetheless provide more
information about a known abnormality. Because
these scans can show more detail from different
angles, they can help in the diagnosis of cleft lip.
This can help doctors to plan the repair after birth.
3D scanning can also be useful to look at the heart
and other internal organs. As a result, some fetal
medicine units do use 3D scans, but only when
they're medically necessary.
132. There’s no evidence to suggest that the scans
aren’t safe, and most mums-to-be gain
reassurance from them. Nonetheless, any type
of ultrasound scan should only be performed by
a trained professional, for as short a time and at
the lowest intensity, as possible.
If you’d like a 3D or 4D scan you’ll probably
need to arrange it privately, and pay a fee. The
clinic may also give you a recording of the scan
on DVD, though this is likely to cost extra.
133. The special transducers and software required to
do 3D and 4D scans are expensive. There are few
clear medical benefits, and experts say they
should only be done if there's a medical need. So
it's unlikely that these scans will replace normal
2D scans used for routine maternity care in the
NHS.
If you decide to have one, the best time to have a
3D or 4D scan is when you're between 26 weeks
and 30 weeks pregnant.
134. Before 26 weeks your baby has very little fat under
her skin, so the bones of her face will show through.
After 30 weeks, your baby's head may go deep
down in your pelvis, so you may not be able to see
her face.
If the placenta is at the front of your womb (uterus),
known as anterior placenta, you'll get the best
images of your baby if you wait until 28 weeks.
It's natural that you'd like to see your baby's face on
the scan. But sometimes it's not possible,
depending on how she's lying.
135. -If she's lying facing outwards, with a good pool of
amniotic fluid around her features, you should be
able to see her face clearly. But if she's facing your
back, her head's far down in your pelvis, or there's
not much fluid around her, you won't see much. The
same applies if you have a lot of tummy fat.
-The sonographer may ask you to go for a walk, or to
come back in a week, when your baby may have
moved to a better position. If it's not possible to get
good views of her face, you may be able to see her
fingers and toes instead.
136. 3D and 4D ultrasound in fetal cardiac
scanning
137. • Over the last decade we have been witness to
a burgeoning literature on three-dimensional
(3D) and four-dimensional (4D) ultrasound-
based studies of the fetal cardiovascular
system. Recent advances in the technology of
3D/4D ultrasound systems allow almost real-
time 3D/4D fetal heart scans.
138. • It appears that 3D/4D ultrasound in fetal
echocardiography may make a significant
contribution to interdisciplinary management
team consultation, health delivery systems,
parental counseling, and professional training.
Our aim is to review the state of the art in 3D/4D
fetal echocardiography through the literature
and index cases of normal and anomalous fetal
hearts.
139. • Three-dimensional (3D) and four-dimensional
(4D) applications in fetal ultrasound scanning have
made impressive strides in the past two decades.
Today, many more centers have 3D/4D ultrasound
capabilities at their command ,and we are witness
to a burgeoning literature of 3D/4Dbased studies.
140. • Perhaps in no other organ system is this recent
outstanding progress so evident as in the fetal
cardiovascular system. Recent technological
developments of motion-gated cardiac scanning
allow almost real-time 3D/4D heart examination.
• It appears from this growing body of literature
that 3D/4D ultrasonography can make a
significant contribution to our understanding of
the developing fetal heart in both normal
• and anomalous cases, to interdisciplinary
management team consultation, to parental
counseling, and to professional training.
141. • These features may work to extend the
benefits of prenatal cardiac screening to
poorly-served areas.
• The introduction of ‘virtual planes’ to fetal
cardiac scanning has helped sonographers
obtain views of the fetal heart not generally
accessible with a standard two-dimensional
(2D) approach.
142. • It is perhaps too early to evaluate whether 3D/4D
cardiac scanning will improve the accuracy of
fetal echocardiography programs.
• However, there is no doubt that 3D/4D
ultrasonography gives us another look at the fetal
heart. The purpose of this review is to summarize
the recent technological advances in 3D/4D fetal
echocardiography , demonstrating their
application through normal and anomalous
cases.
143. 3D/4D TECHNIQUES AND THEIR
APPLICATION TO FETAL CARDIAC
SCANNING
• Spatio-temporal image correlation (STIC)
• STIC acquisition is an indirect motion-gated offline scanning
mode1–4. The automated volume acquisition is made possible by
the array in the transducer performing a slow single sweep,
recording a single 3D data set consisting of many 2D frames one
behind the other.
• The volume of interest (VOI) is acquired over a period of about 7.5
to 30 s at a sweep angle of approximately 20–40◦ (depending on
the size of the fetus) and frame rate of about 150 frames per
second. A 10-second, 25◦acquisition would contain 1500 B-mode
images4. Following acquisition the ultrasound system applies
• mathematical algorithms to process the volume data and detect
systolic peaks, which are used to calculate the fetal heart rate.
145. • The B-mode images are arranged in order
according to their spatial and temporal
domain, correlated to the internal trigger, the
systolic peaks that define the heart cycle4
(Figure 1).
146. • The resultant 40 consecutive volumes are a
reconstructed complete heart cycle that displays
in an endless loop.
• This cine-like file of a beating fetal heart can be
manipulated to display any acquired scanning
plane at any stage in the cardiac cycle (Figure 2).
• While a complex process to describe, this
reconstruction takes place directly following the
scan in a matter of seconds;
148. • the STIC acquisition can be reviewed with the
patient still present and repeated if necessary, and
saved to the scanning machine or a network.
Optimal STIC acquisition technique for examination
of the fetal heart is thoroughly.
• In post-processing, various methodologies have
been proposed to optimize the acquisition to
demonstrate the classic planes of fetal
echocardiography6,7 (Figure 3), as well as ‘virtual
planes’ that are generally inaccessible in 2D cardiac
scanning8–11.
150. • These views once obtained are likewise stored in the
patient’s file, in addition to the original volume,
either as static images or 4D motion files. Any of the
stored information can be shared for expert review,
interdisciplinary consultation, parental counseling, or
teaching.
• STIC is an acquisition modality that can be combined
with other applications by selecting the appropriate
setting before acquisition (B-flow, color and power
Doppler, tissue Doppler, high-definition flow Doppler)
or with post processing visualization modalities (3D
volume rendering, inversion mode, tomographic
ultrasound imaging).
151. • By moving the point the operator manipulates the
volume to display any plane within the volume; if
temporal information was acquired, the same plane
can be displayed at any stage of the scanned cycle.
• From a good STIC acquisition the operator can
scroll through the acquired volume to obtain
sequentially each of the classic five planes6 of fetal
echocardiography, and any plane may be viewed at
any time-point throughout the reconstructed
cardiac cycle loop. The cycle can be run or stopped
frame-by-frame to allow examination of all phases
of the cardiac cycle, for example opening and
closing of the atrioventricular valves.
152. • By comparing the A- and B-frames of the MPR
display, the operator can view complex cardiac
anatomy in corresponding transverse and
longitudinal planes simultaneously. So, for example,
an anomalous vessel that might be disregarded in
cross-section is confirmed in the longitudinal plane.
• 3D rendering is another analysis capability of an
acquired volume. It is familiar from static 3D
applications, such as imaging the fetal face in surface
rendering mode. In fetal echocardiography it is
readily applied to 4D scanning.
153. • The operator places a bounding box around the region of
interest within the volume (after arriving at the desired
plane and time) to show a slice of the volume whose depth
reflects the thickness of the slice.
• For example, with the A-frame showing a good four
chamber view, the operator places the bounding box tightly
around the interventricular septum. The rendered image in
the D-frame will show an ‘en face’ view of the septum. The
operator can determine whether the plane will be
displayed from the left or right, i.e. the septum from within
the left or the right ventricle; the thickness of
• the slice will determine the depth of the final image, for
example to show texture of the trabeculations within the
right ventricle (Figure 4).
155. • TUI is a more recent application that extends the
capabilities of MPR and rendering modes. This multislice
analysis mode resembles a magnetic resonance imaging
or computer-assisted tomography display. Nine parallel
slices are displayed simultaneously from the plane of
interest (the ‘zero’ plane), giving sequential views from
−4 to +4. The thickness of the slices, i.e. the distance
between one plane and the next, can be adjusted by the
operator. The upper left frame of the display shows the
position of each plane within the region of interest,
relative to the reference plane. This application has the
advantage of displaying sequential parallel planes
simultaneously, giving amore complete picture of the
fetal heart (Figure 5).
157. • 3D/4D with color Doppler, 3D power Doppler (3DPD)
and 3D high definition power flow Doppler Color and
power Doppler have been extensively applied to fetal
echocardiography; one could hardly imagine
performing a complete fetal echo scan today without
color Doppler. Color or power Doppler, and the most
recent development, high definition flow Doppler, can
be combined with static 3D direct volume non-gated
scanning to obtain a 3D volume file with color Doppler
information or 3DPD (one-color) volume files.
• Color Doppler can be used more effectively in 3D/4D
ultrasonography when combined with STIC
acquisition12 in fetal echocardiography, resulting in a
volume file that reconstructs the cardiac cycle, as
above, with color flow information.
158. • This joins the Doppler flow to cardiac events2 and
provides all the advantages of analysis (MPR,
rendering, TUI) with color. This combination of
modalities is very sensitive for detecting intracardiac
Doppler flow through the cardiac cycle, for example
mild tricuspid regurgitation that occurs very early in
systole or very briefly can be clearly seen.
• Extreme care must be taken when working with
Doppler applications in post-processing, however, to
avoid misinterpretation of flow direction as the volume
is rotated.
159. • 3DPD is directionless, one-color Doppler that is
most effectively joined with static 3D scanning2.
3DPD uses Doppler shift technology to reconstruct
the blood vessels in the VOI, isolated from the rest
of the volume. Using the ‘glass body’ mode in post-
processing, surrounding tissue is eliminated and the
vascular portion of the scan is available in its
entirety for evaluation. The operator can scroll
spatially to any plane in the volume (but not
temporally: in this case, color Doppler with STIC is
more effective, see above).
160. • 3DPD can reconstruct the vascular tree of the
fetal abdomen and thorax14,15, relieving the
operator of the necessity of reconstructing
amental picture of the idiosyncratic course of an
anomalous vessel from a series of 2D planes.
• This has been shown to aid our
• understanding of the normal and anomalous
anatomy and pathophysiology of vascular
lesions16 (Figure 6).
162. • High-definition power flow Doppler, the newest
development in color Doppler applications, uses
high resolution and a small sample volume to
produce images with two-color directional
information with less ‘blooming’ of color for more
realistic representation of vessel size. It depicts flow
at a lower velocity than does color or power
Doppler, and has the advantage of showing flow
direction. It can be combined with static 3D or 4D
gated acquisition (STIC) and the glass-body mode,
to produce high-resolution images of the vascular
tree with bidirectional color coding (Figure 7).
164. • This technique is particularly sensitive for imaging
small vessels. High resolution bidirectional power
flow Doppler combines the flow information
provided by color Doppler with the anatomic
acuity associated with power Doppler. Owing to
this modality’s sensitivity systolic and diastolic
flow are observed at the same time, for example,
when used with STIC acquisition the ductus
venosus is shown to remain filled both in systole
and in diastole.
165. • Inversion mode (IM)
• IM is another post-processing visualization modality that can
be combined with static 3D or STIC acquisition.IM analyzes
the echogenicity of tissue (white) and fluid-filled areas (black)
in a volume and inverts their presentation, i.e. fluid-filled
spaces such as the cardiac chambers now appear white, while
the myocardium has disappeared. In fetal echocardiography it
can be applied to create ‘digital casts’ of the cardiac chambers
and vessels. It can also produce a reconstruction of the extra
cardiac vascular tree, similar to 3DPD. IM has the additional
advantage of showing the stomach and gall bladder as white
structures, which can aid the operator in navigating within a
complex anomaly scan. Most recently, IM has been joined
with STIC to quantify fetal cardiac ventricular volumes, which
may prove useful in the evaluation of fetal heart function.
166. • B-flow
• B-flow is an ‘old-new’ technology that images blood
flow without relying on Doppler shift. B-flow is an
outgrowth of B-mode imaging that, with the advent of
faster frame rates and computer processing, allows the
direct depiction of blood cell reflectors. It avoids some
of the pitfalls of Doppler flow studies, such as aliasing
and signal dropout at orthogonal scanning angles. The
resulting image is a live gray-scale depiction of blood
flow and part of the surrounding lumen, creating
sensitive ‘digital casts’ of blood vessels and cardiac
chambers (Figure 8).
167. • This also makes B-flow more sensitive for volume
measurement. When applied to 3D fetal
echocardiography B-flow modality is a direct
volume non-gated scanning method able to show
blood flow in the heart and great vessels in real-
time, without color Doppler flow information
169. SCREENING EXAMINATION OF THE
FETAL HEART WITH 3D/4D
ULTRASOUND
• Guidelines for the performance of fetal heart examinations
have been published by the International Society of
Ultrasound in Obstetrics and Gynecology (ISUOG).These
guidelines for ‘basic’ and ‘extended basic’ fetal cardiac
scanning are amenable to 3D/4D applications, and 3D/4D can
enhance both basic and extended basic fetal cardiac scans, as
well as evaluation of congenital anomalies. Many research
teams have applied 3D ultrasound and STIC acquisition to
fetal echocardiography, and various techniques have been put
forward to optimize the use of this modality. A well-executed
STIC acquisition5 contains all the necessary planes for
evaluation of the five classic transverse planes of fetal
echocardiography.
170. • The operator can examine the fetal upper abdomen
and stomach, then scroll cephalad to obtain the
familiar four chamber view, the five-chamber view,
the bifurcation of the pulmonary arteries, and
finally the three-vessel and trachea view. Slight
adjustment along the x- or y-axis may be necessary
to optimize the images. Performed properly, this
methodology will provide the examiner with all the
necessary planes to conform with the guidelines.
However, it must be remembered that STIC
acquisition that has been degraded by maternal or
fetal movements, including fetal breathing
movements, will contain artifacts within the scan
volume.
171. POTENTIAL PITFALLS OF 3D/4D
ECHOCARDIOGRAPHY
• 3D/4D fetal echocardiography scanning is prone
to artifacts similar to those encountered in 2D
ultrasonography, and some that are specific to
3D/4D acquisition and post-processing.
172. STIC acquisition quality
• The quality of a STIC acquisition may be adversely
affected by fetal body or ‘breathing’ movements;
quality is improved by scanning with the fetus in
a quiet state, and using the shortest scan time
possible. When reviewing a STIC acquisition, the
B-frame will reveal artifacts introduced by fetal
breathing movements (Figure 9). If the B-frame
appears sound, the volume is usually acceptable,
and can be used for further investigation. It must
be stressed again that the quality of the original
acquisition will affect all further stages of post-
processing and evaluation.
174. ACCURACY
• Several studies have compared imaging yield
between 2D and 3D/4D fetal echocardiography,
others have examined the feasibility of 3D/4D and
STIC in screening programs, while others have
described the application of various 3D/4D
modalities to the diagnosis or evaluation of fetal
cardiovascular anomalies. However, no large study
has examined the contribution of 3D/4D
ultrasonography to the accuracy of fetal
echocardiography screening programs.
175. • In coming years, studies will direct 3D/4D capabilities to
the evaluation of fetal cardiac functional parameters.
This may provide insights into the physiological effects
of fetal structural or functional cardiac defects, or
maternal diseases such as diabetes, on the developing
fetus. To the best of our knowledge, no large study has
been performed to date to examine whether the
addition of 3D/4D methods to fetal echocardiography
screening programs increases the detection rate of
cardiac defects. This technology has reached the stage
when its reproducibility and added value in screening
accuracy should be tested in large prospective studies,
not only by teams or in centers that have made 3D/4D
their specialty, but among the generality of
professionals performing fetal echocardiography.
176. REFERENCES
• 1. DeVore GR, Falkensammer P, Sklansky MS, Platt LD. Spatiotemporal
image correlation (STIC): new technology for evaluation of the fetal
heart. Ultrasound Obstet Gynecol 2003;22: 380–387.
• 2. Deng J. Terminology of three-dimensional and four-dimensional
ultrasound imaging of the fetal heart and other moving body
parts.Ultrasound Obstet Gynecol 2003; 22: 336–344.
• 3. Goncalves LF, Lee W, Chaiworapongsa T, Espinoza J,Schoen ML,
Falkensammer P, Treadwell M, Romero R. Fourdimensional
ultrasonography of the fetal heart with spatiotemporal image correlation.
Am J Obstet Gynecol 2003; 189:1792–1802.
• 4. Falkensammer P. Spatio-temporal image correlation for volume
ultrasound. Studies of the fetal heart. GE Healthcare: Zipf, Austria, 2005.
• 5. Goncalves LF, Lee W, Espinoza J, Romero R. Examination of the fetal
heart by four-dimensional (4D) ultrasound with spatiotemporal image
correlation (STIC). Ultrasound Obstet Gynecol 2006; 27: 336–348.
177. 3D – 4D Ultrasound in Obstetrics and
Gynecology
178. • Three dimensional (3D) ultrasound (USG) and 4D i.e. real
• time 3D are a natural development of the imaging technology
• and were first demonstrated nearly 15 years ago, but are
• becoming a clinical reality only now. Methods for 3D
• reconstruction of CT and MRI images have achieved an
• advanced state of development. 3D applications in ultrasound
• have lagged behind CT and MRI, because ultrasound data is
• much more difficult to render in 3D. Only in the past few
• years has the computing power of ultrasound equipment
• reached a level adequate enough for the complex signal
• processing tasks needed to render ultrasound data in three
• dimensions. The clinical application of 3D ultrasound is likely
• to advance rapidly, as improved 3D rendering technology
• becomes more widely available
179. • The advantages of 3D and 4D ultrasound in certain areas
• are unequivocal. Most centres already apply its use in the
• workup of fetal anomalies involving the face, limbs,
• thorax, spine and the central nervous system. The use of
• this technology in applying color doppler, in guiding
needles
• for different puncture procedures as well in evaluating
• the fetal heart are currently under close research scrutiny.
180. • 3D ultrasound helps the bonding between the parents and
• their future offspring, and consultants understand fetal
• pathology better and can plan postnatal interventions better.
• The multiplanar presentation and niche mode are quite
• useful to determine the extension –inside or outside the
• organs, of nodules, cysts or tumors. The volume
• measurement is better assessed with 3D and we can
• perform studies that follow growth in order to decide
• medical or surgical treatment. The VOCAL(R) makes it
• possible to obtain a proper after-treatment follow-up of
• focal disorders in these small organs. Neovascularization
• is clearly viewed with 3D USG and probably can suggest
• malignant origin of a neoplasm. 3D USG offers a more
• comprehensive image of anatomical structures and
• pathological conditions and also permits observation of
• the exact spatial relationships
181. • More studies are needed to demonstrate specificity
and
• sensitivity of 3D and 4D USG. There are limitations to
• adequate visualization of fetal anatomy with 3D/4D
• technology. If there is inadequate amniotic fluid
surrounding
• the fetus, or if the fetus has its face in the posterior
position in the uterus, there will be difficulty visualizing
structures
• and the face.
182. • 3D allows a simultaneous display of multiple
• sequential parallel planes of the fetal structures, but there is
• some uncertainty if an isolated image in one of the multislice
• images represents the exact level of a fetal structure.
• Another problem is the creation of false expectations and
• overall the medical value is limited. Pregnant women will
• ask for a picture of their fetus like those they have seen in
• advertisements and put pressure on the scanning centres.
• Such is the demand in the United States that technician
• operated 4D ultrasounds are readily available in scanning
• booths in shopping malls, enabling parents to purchase a
• video of their moving fetus. This creates problems later on
• when women, having already had such USG, do not realise
• that they need a targeted anomaly scan
183. • Endometrial thickness, endometrial pattern, pulsatility index
• (PI) and resistance index (RI) of uterine vessels, endometrial
• volume, vascularization index (VI), flow index (FI) and
• vascularization flow index (VFI) of endometrial and subendometrial
• regions have been studied by 3D with power
• dopplers on the day of oocyte retrieval in patients undergoing
• the first IVF cycle. Uterine RI, endometrial VI and VFI were
• significantly lower in the pregnant group than in the nonpregnant
• group. There was a nonsignificant trend of higher
• implantation and pregnancy rates in patients with absent
• endometrial or subendometrial blood flow. The number of
• embryos replaced and endometrial VI were the only two
• predictive factors for pregnancy.
184. • Endometrial and subendometrial
• blood flows measured by 3D power doppler
• ultrasound were not good predictors of pregnancy if
they
• were measured at one time-point during IVF treatment
6,7. A
• similar study noted that endometrial volume
decreased
• significantly after hCG injection in women who
conceived,
• but not in those who did not.
185. • Along with crown-rump length (CRL), the size (diameter)
• of embryonic structures such as gestational sac (GS) and
• yolk sac (YS) may have prognostic value for embryonic
• development. First trimester volume calculations of these
• structures using transvaginal 3D USG technic have been
• done. Volumetry of GS proved to be a sensitive predictor
• for pregnancy outcome and can be a good supplement to
• CRL measurements. However, no statistically significant difference
was found when YS volumes of normal and
• abnormal pregnancies were compared. Specificity, sensitivity,
• positive and negative predictive values of GS volumes and
• CRL were similar. Mean YS/GS ratios also had good
• predictive values (P <0.05)
186. • 4D was successfully used to perform amniocentesis, CVS,
• cordocentesis, and intrauterine transfusion. Using 4D USG
• guidance, most procedures were performed within 5 minutes
• and with a 100% success rate, even in cases involving severe
• oligohydramnios, thin placenta and narrow umbilical veins.
• Moreover, there were no serious complications during or
• after any procedure. This appeared to contribute to the
• accuracy of needle placement by eliminating the lateralization
• phenomenon when a fixed needle guide attachment was used.
• Needle tip visualization was seen in each orthogonal plane in
• most freehand 4D amniocentesis cases
187. • Presently, both 2D and 4D methods are required for the
• assessment of early fetal motor development and motor
• behaviour. Several movement patterns, such as sideway
• bending, hiccup, breathing movements, mouth opening and
• facial movements could be observed only by 2D USG 11.
• Isolated hand movement and subtypes of hand movements
• were easily recognized by 4D USG. All subtypes of hand to
• head movement can be seen from 13 weeks of gestation
• with fluctuating incidence. Facial activities and different
• forms of expression are easily recognized. 4D USG is superior
• over real time 2D USG for qualitative, but inferior for
• quantitative analysis of hand movements. 4D USG makes it
• possible to determine the exact direction of the fetal hand,
• but the exact number of each type of hand movements can
• still not be determined.4D USG is superior to 2D USG in the
• evaluation of complex facial activity and expression.
188. • Among
• facial activities observed by 4D USG, simultaneous eyelid
• and mouth movements dominate between 30 and 33 weeks
• of gestation. Pure mouth movements such as mouth opening,
• tongue expulsion, yawning and pouting are present, but at a
• significantly lower incidence. Facial expressions such as
• smiling and scowling can be precisely observed using 4D
• USG 12. There were no movements observed in fetal life that
• were not present in neonatal life; the Moro reflex was present
• only in neonates
189. • Inclusion of 3D and 4D ultrasound imaging in the examination
• of cleft lip and/or palate, allows easier and more rapid
• screening and more precise evaluation of the different cleft
• constituents 14. 3D USG can be a reliable technic for
• visualizing most fetal cranial sutures and fontanels. By
• performing a sagittal and a transverse scan, most of the
• sutures and fontanels can be made visible during the second
• half of pregnancy. Visualization depends on gestational age
• 15. Gray-scale and color doppler dynamic 3D displays and
multiplanar views used to assess cardiac gating and cardiac
• morphology demonstrate clinically useful 4D images of the
• fetal heart. The reconstruction of 3D and multiplanar views
• provided additional views not obtainable by 2D imaging
190. • 3D echocardiography can provide estimates of ventricular
• volume and function and may in future be used for evaluation
• of fetuses with congenital heart disease and cardiac
• dysfunction 17. Spatio-temporal image correlation in
• combination with color doppler USG is a promising new
• tool for multiplanar and 3D/4D rendering of the fetal heart.
• Limitations may be found later in gestation in fetuses with
• large hearts and early in gestation as a result of low
• discrimination of signals. In addition, insonation perpendicular
• to the structure of interest does not image color doppler
• signals and should be avoided during acquisition 18. There is
• a potential value of 3D power doppler in prenatal diagnosis
• and monitoring of pregnancies complicated by large,
• vascularized placental chorioangioma 19. No significant
• differences are shown between 2D and 4D ultrasound
• placental scanning
191. • 3D power doppler ultrasound provides a useful tool to
• investigate intratumor vascularization and volume of cervical
• cancer 21. Alterations of 3D USG derived vascular indices
• were found in patients with cervical cancer and some
• vascular indices proved to be associated with tumor size 22.
• In a small group of pelvic masses that appear malignant on
• B-mode USG, the use of 3D quantification of tumor
• vascularity yields a diagnostic accuracy that is similar to
• that of subjective evaluation of vascularity 23. 3D powerdoppler
• imaging does not have a better diagnostic
• performance than 2D power doppler imaging in the
• discrimination of benign from malignant complex adnexal
• masses 24. Endometrial volume and thickness measurements
• by 3D and 2D USG, in patients with postmenopausal
• bleeding, show good reproducibility but the reproducibility
• of 3D ultrasound is better
192. • Rectovaginal septal defects are
• readily identified on translabial 3D USG as a herniation of
• rectal wall and its contents into the vagina. Approximately
• one third of clinical rectoceles do not show a sonographic
• defect, and the presence of a defect is associated with age,
• not parity 26. While 3D pelvic floor imaging is a field that is
• still in its infancy, it is already clear that the method has
• opened up entirely new opportunities for the observation
of
• functional anatomy.
193. • The exact applicability of 3D and 4D USG is yet to be
• ascertained. The American Institute of Ultrasound in
Medicine
• has convened a panel of physicians and scientists with
interest
• and expertise in 3D USG to discuss the current diagnostic
• benefits and technical limitations in obstetrics and
gynecology
• and to consider the utility and role of this type of imaging
in
• clinical practice now and in the future
194. References
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• in Ultrasound, CT & MR. 2001;22:85-105.
• 2. Timor-Tritsch IE, Han E, Platt LD. Three-dimensional ultrasound
• experience in obstetrics. Curr Opin Obstet Gynecol 2002;14:569-
• 75.
• 3. Maymon R, Herman A. Ariely S et al. Three-dimensional vaginal
• sonography in obstetrics and gynaecology. Hum Reprod Update
• 2000; 6:475-84.
• 4. Fernandez LJ, Aguilar A, Pardi S. Three-dimensional ultrasound in
• small parts: Is it just a nice picture? Ultrasound Quarterly
• 2004;20:119-25.
• 5. Leung KY, Ngai CSW, Chan BC et al. Three-dimensional extended
• imaging: a new display modality for three-dimensional ultrasound
• examination. Ultrasound Obstet Gynecol. 2005; 26:244-51.
• 6. Ng EHY, Chan CCW, Tang OS et al. The role of endometrial and
• subendometrial blood flows measured by three-dimensional power
• Doppler ultrasound in the prediction of pregnancy during IVF
• treatment. Hum Reprod 2006; 21:164-70.