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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5786_Библиотеки_им_академика_М_И_Перельмана.pdf
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MONOAMNIOTIC TWINS
Monoamniotic twinning occurs in 5% of monochorionic twins (1% of all twins),
and the most severe form of splitting disorders in monozygotic twins is conjoined
twins. At the 10–14-week scan, the criteria for monoamnionicity are the absence
of the intertwin amniotic membrane and the presence of only one yolk sac7 and
it should be suspected if the placental cord insertions are close to each other and
an unusual intrauterine position of both fetuses, in close proximity to each other,
is seen.25 Monoamniotic twins show a significantly increased risk for structural
anomalies and for poor perinatal outcome, even in the absence of an intertwin
discordance. In both structurally normal and abnormal twins, cord entanglement,
which has been reported to be present as early as the first trimester,2 has been
responsible for the demise of one or both fetuses in the majority of cases.
The aim of fetal surveillance should be to reach at least 32 weeks of gestation and delivery by elective caesarean section should be performed to avoid
acute cord complications during delivery. Cord entanglement may be detected
by colour Doppler ultrasound. However, its consequences remain controversial,
Ultrasound in obstetrics and gynaecology
because the incidence of loose entanglement seems to be high, but fetal jeopardy occurs only if this leads to compression of the cords, which may be an acute
event.
The primary ultrasound feature of conjoined twins is the fact that they are
always close to each other with common movement patterns and without separation from each other if observed over a certain period of time. The chance for
survival depends on the site of conjoining and the organs involved, and overall
about 50% are stillborn. One third of the live-born twins have defects, which are
impossible to correct surgically, and in those cases where surgery is attempted,
a survival rate of about 60% of babies is achieved.
30
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HIGHER-ORDER MULTIPLE PREGNANCIES
Recently the incidence for multiples of a higher order has increased due to the
use of different techniques in assisted reproduction. The use of transvaginal and
transabdominal ultrasound to assess the number of fetuses and their chorionicity is fundamental in the early diagnosis and management of these pregnancies.
With the measurement of the nuchal translucency, the individual fetal risk for
chromosomal abnormalities and other maldevelopments can be calculated and
a selective reduction can be performed under ultrasound guidance to reduce
the perinatal risk associated with multiples of higher order than twins or triplets. Multifetal reduction has been reported to reduce triplets to twins5 and the
risk for fetal loss after the procedure has been continuously diminishing during
recent years, as more experience in this technique has been gained. In general,
the higher the starting number of fetuses, the poorer is the outcome after reduction, with fetal loss rates reported to range from 15.4% to 4.5% according to
starting numbers ranging from six to three fetuses, respectively.
13,14
References
1. Appleman Z, Vinkler C, Caspi B. Chorionic
villous sampling in multiple pregnancies.
Eur J Obstet Gynecol Reprod Biol
1999;85:979
2. Arabin B, Laurini RN, van Eyck J. Early
prenatal diagnosis of cord entanglement
in monoamniotic multiple pregnancies.
Ultrasound Obstet Gynecol 1999;13:
181–186
3. Bajoria R, Wee LY, Anwar S, Ward S.
Outcome of twin pregnancies complicated
by single intrauterine death in relation to
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placenta. Hum Reprod 1999;14:2124–2130
4. Baldwin VJ. The pathology of
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VJ (ed) Pathology of multiple pregnancy.
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5. Boulot P, Vignal J, Vergnes C, Dechaud H,
Faure JM, Hedon B. Multifetal reduction of
triplets to twins: a prospective comparison
of pregnancy outcome. Hum Reprod
2000;15:1619–1623
6. Brodtkorb E, Myhr G, Gimse R. Is
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7. Bromley B, Benacerraf B. Using the number
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8. Chitrit Y, Filidori M, Pons JC, Duyme M,
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12. Diehl W, Hecher K, Zikulnig L, Vetter M,
Hackelöer BJ. Placental vascular
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laser surgery in severe mid-trimester
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13. Evans MI, Goldberg JD, Horenstein J
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14. Evans MI, Berkowitz RL, Wapner RJ et al.
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2001;184:97–103
15. Farina A, Vesce F, Garutti P, Jorizzo G,
Bianciotto A. Evaluation of intrauterine
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biparietal diameter, femur length and
abdominal circumference. Gynecol Obstet
Invest 1999;48:14–17
16. Gaziano EP, De Lia JE, Kuhlmann RS.
Diamniotic monochorionic twin gestations: an
overview. J Matern Fetal Med 2000;9:89–96
17. Hatkar PA, Bhide AG. Perinatal outcome of
twins in relation to chorionicity. J Postgrad
Med 1999;45:33–37
18. Hecher K, Diehl W, Zikulnig L, Vetter M,
Hackelöer BJ. Endoscopic laser coagulation
of placental vascular anastomoses in 200
pregnancies with severe mid-trimester twinto-twin transfusion syndrome. Eur J Obstet
Gynecol Reprod Biol 2000;92:135–139
19. Isada NB, Sorokin Y, Drugan A, Johnson MP,
Zador I, Evans MI. First trimester interfetal
size variation in well-dated multifetal
pregnancies. Fetal Diagn Ther 1992;7:82–86
20. Jenkins TM, Wapner RJ. First trimester
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sampling. Semin Perinatol 1999;23:403–413
21. Landy HJ, Weiner S, Corson SL, Batzer
FR, Bolognese RJ. The ‘vanishing twin’:
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disappearance in the first trimester. Am J
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22. Loos R, Demron C, Vlietinick R, Demron R.
The East Flanders prospective twin survey
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23. Manzur A, Goldsman MP, Stone SC,
Frederick JL, Balmaceda JP, Asch RH.
Outcome of triplet pregnancies after
assisted reproductive techniques: how
frequent are the vanishing embryos? Fertil
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24. Pandya P. Ultrasound and multiple
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25. Sebire NJ, Souka A, Skentou H, Geerts L,
Nicolaides KH. First trimester diagnosis of
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26. Sebire NJ, Souka A, Skentou H, Geerts L,
Nicolaides KH. Early prediction of severe
twin-to-twin transfusion syndrome. Hum
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27. Sepulveda W, Sebire NJ, Hughes K,
Odibo A, Nicolaides KH. The lambda sign
at 10-14 weeks of gestation as a predictor of
chorionicity in twin pregnancies. Ultrasound
Obstet Gynecol 1996;7:421–423
28. Sherer DM. Is less intensive fetal
surveillance of dichorionic twin gestations
justified? Editorial. Ultrasound Obstet
Gynecol 2000;15:167–173
29. Snijders RJM, Noble P, Sebire NJ,
Souka AP, Nicolaides KH. UK multicentre
project on assessment of risk for trisomy
21 by maternal age and fetal nuchal
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translucency at 10–14 weeks of gestation.
Fetal Medicine Foundation First Trimester
Screening Group. Lancet 1998;352:
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30. Spitz L. Conjoined twins. Br J Surg
1996;83:1028–1030
31. van den Berg C, Braat AP, Van Opstal D
et al. Amniocentesis or chorionic villous
sampling in multiple gestations? Experience
with 500 cases. Prenat Diagn 1999;19:
234–244
32. Victoria A, Mora G, Arias F. Perinatal
outcome, placental pathology, and
severity of discordance in monochorionic
and dichorionic twins. Obstet Gynecol
2001;97:310–355
33. Zikulnig L, Hecher K, Bregenzer T, Bäz E,
Hackelöer BJ. Prognostic factors in severe
twin–twin transfusion syndrome treated by
endoscopic laser surgery. Ultrasound Obstet
Gynecol 1999;14:380–387
34. Kalish RB, Gupta M, Perni SC, Berman
S, Chasen ST. Clinical significance of first
trimester crown–rump length disparity in
dichorionic twin gestation. Am J Obstet
Gynecol 2004;191:1437–1440
35. Machin GA. Why is it important to diagnose
chorionicity and how do we do it? Best Pract
Res Clin Obstet Gynecol 2004;18:515–530
36. Menon DK. A retrospective study of the
accuracy of sonographic chorionicity
determination in twin pregnancies. Twin
Res Hum Genet 2005;8:259–261
37. Geipel A, Berg C, Katalinic A et al. Prenatal
diagnosis and obstetric outcomes in triplet
pregnancies in relation to chorionicity. Br J
Obstet Gynaecol 2005;112:554–558
38. Van der Cruys, Faiola S, Auer M, Sebire N,
Nicolaides KH. Screening for trisomy 21
in monochorionic twins by measurement
of fetal nuchal translucency thickness.
Ultrasound Obstet Gynecol 2005;25:
551–553
39. Wald NJ, Rish S, Hackshaw AK. Combining
nuchal translucency and serum markers
in prenatal sceening for Down syndrome
in twin pregnancies. Prenat Diagn
2003;23:588–592
40. Garne E, Andersen HJ. The impact of
multiple pregnancies and malformations
on perinatal mortality. J Perinat Med
2004;32:215–219
41. Huber A, Hecher K. How can we diagnose
and manage twin-twin transfusion
syndrome? Best Pract Res Clin Obstet
Gynaecol 2004;18:543–556
42. Fisk NM, Tan TY, Taylor MJ. Stagesaved treatment of twin-twin transfusion
syndrome. Am J Obstet Gynecol
2004;190:1491–1492
43. Robyz R, Quarello E, Ville Y. Management
of fetofetal transfusion syndrome. Prenat
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Three-dimensional and four-dimensional ultrasound application in prenatal diagnosis
Rabih Chaoui Bernard Benoit
ABSTRACT
Three-dimensional ultrasound has been the most rapidly evolving technique
in fetal imaging in recent years and is mainly known for the demonstration
of the face or other fetal surface structures. The potential of this technique in
prenatal diagnosis is, however, greater, based on the possibility of acquiring a
volume data set of a region of interest which can then be displayed in different
ways. This chapter will emphasize these display modes as the demonstrations
of reconstructed two-dimensional images either as orthogonal or parallel crosssection planes (tomographic mode) or the rendering of the three-dimensional/
four-dimensional information. Rendering includes the surface mode, the
maximum, minimum and inversion modes, as well as glass body mode when
combined with colour or power Doppler acquisition. Spatial and temporal image
correlation technology enables the acquisition of fetal heart data and the display
of one single cardiac cycle in different modes. The chapter supports the idea that
we are now moving from the era of ‘sonography in two-dimensional planes’ to
‘volume ultrasound’.
KEYWORDS
Inversion mode, maximum mode, minimum mode, prenatal diagnosis, spatial and
temporal image correlation, three-dimensional ultrasound, tomographic imaging,
volume ultrasound.
INTRODUCTION
Three-dimensional (3D) ultrasound has become the most rapidly evolving
technique in fetal imaging, but some examiners are still using 3D and fourdimensional (4D) techniques only to demonstrate the fetal face to the parents,
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which has made this new technique very popular with them as well. However,
the concept of ‘volume ultrasound’ introduced a few years ago enabled a more
comprehensive medical and clinical application of 3D technology to prenatal diagnosis.1 A volume data set of the region of interest is acquired digitally,
and the information stored can be displayed in different ways to highlight the
spatial arrangement of a specific structure in the region of interest. Many colleagues may still be unfamiliar with all of these features, which are now well
established in targeted prenatal diagnosis for ruling out or clearly demonstrating fetal malformations. In this chapter we will review the potential of volume
ultrasound and the application of some display modes in clinical work.
VOLUME ACQUISITION
A volume data set can be acquired in different ways. The acquisition can be
achieved as a:
static 3D
Ultrasound in obstetrics and gynaecology
•
real-time 3D or 4D
•
spatial and temporal image correlation for heart and vessels.
•
STATIC 3D
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This is the 3D used in most fetal studies (face, hands, etc.) and consists of a
single volume data set. The volume quality is defined by the choice of the
acquisition time. Static 3D can also be combined with colour Doppler, power
Doppler, high-definition (HD) flow, and B-flow, depending on the question of
interest.
REAL-TIME 3D OR 4D ULTRASOUND
Real-time 3D or 4D is achieved today mainly by a mechanical 3D transducer
with a rapid acquisition from 1.5 to 40 volumes/sec. A few matrix transducers
provide electronic 3D information but their use in obstetric ultrasound is still
limited. The advantage of a 4D examination is its ease of use. The direct result
on the screen enables online manipulation to acquire the best image by changing the gain and the contrast depending on the mode used. Furthermore, it allows
the transducer to be moved depending on the insonation angle. The technique is
ideal for studying fetal movements and behaviour throughout pregnancy (smiling, yawning, grimacing, etc.). It can also be used for fetal echocardiography but
this requires a great deal of experience.
SPATIAL AND TEMPORAL IMAGE CORRELATION
Spatial and temporal image correlation (STIC) is a software application providing an acquisition of a fetal heart volume data set over a period of few
seconds (i.e. 7.5–15 sec). It allows the acquisition of numerous planes including
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additional information from an entire cardiac cycle. The software calculates the
mean heart rate acquired and the images in the volume are rearranged according to their temporal event within the heart cycle. The displayed volume then
includes a single ‘hypothetical’ heart cycle, which is reconstructed from single
selected images of the A-plane (acquisition plane) in the different phases of the
heart cycle, whereas the B- and C-planes are reconstructed digitally.2 STIC can
be used with grey-scale fetal echocardiography but can also be combined with
colour Doppler, power Doppler, HD flow, B-flow, etc.3 Once the acquisition of
a volume is achieved, the information can be visualized as either single or multiple 2D images regenerated from the volume and selected by the examiner or
as a volume spatial information called 3D rendering, allowing the application of
different modes. Some of the actual display modes will be emphasized and illustrated in this chapter.
VOLUME DATA DISPLAY
SINGLE PLANE OF CHOICE, MULTIPLANAR ORTHOGONAL PLANES OR MULTIPLE TOMOGRAPHIC PARALLEL SLICES
From a digitally stored 3D/4D data set, cross-sectional views can be obtained
at any desired orientation (a so-called ‘anyplane’), direction and depth. It must
be borne in mind that the acquisition (A-) plane provides the best information,
whereas the reconstructed planes (B-, C- or others) are of lesser quality. This
should be considered during the volume acquisition. The 2D image analysis from
a volume can be achieved from a 3D, 4D or STIC data set. The display format
is either a single-plane view or a multiplanar view showing three planes which
are perpendicular to each other (Fig. 14.1). In the lateral view the intersection
of the three planes is a dot and by moving the position of this dot, the examiner can navigate through the volume (see Fig. 14.1). The recent introduction of
multislice analysis known as tomographic ultrasound imaging (TUI) is similar to
the tomographic assessment known from computed tomography (CT) and magnetic resonance (MR) workstations (Figs 14.2, 14.3). The examiner can define
the slice thickness and the number of planes demonstrated. The multiplanar
mode can be used to acquire a plane not directly seen on cross-section 2D during
live examination, mainly in cases with non-optimal fetal position, so as to demonstrate the corpus callosum, a fetal profile, a limb or the aortic arch. It can be
used to visualize exact midline planes after making adjustments in the two other
orthogonal planes (for nasal bone assessment).
One of the major advantages of a 3D data set is the potential for offline examination of a few volumes at a remote station.
this mode could be the transfer of data via the Internet to a remote site to get a
second opinion or a complete offline evaluation without examining the patient.5
However, since the quality of reconstructed images depends mainly on the original acquisition, the examiner should consider this aspect when acquiring volumes
for future studies.
4
One of the future potential uses of
Three-dimensional and four-dimensional ultrasound application in prenatal diagnosis
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Ultrasound in obstetrics and gynaecology
262
Fig. 14.1 Volume data set of a fetal face shown with the ‘multiplanar mode’ with three
orthogonal planes. The dot is the intersection of all three planes and can be used to achieve
the best position for assessing the profile. In the C-plane (lower panel) the dot is on the nasal
bone. In the lower panel in another fetus the volume information of the face was used to
achieve a plane of the soft palate after offline processing.
Fig. 14.2 Tomographic ultrasound imaging (TUI) of the brain demonstrating all important
brain structures including the lateral ventricles, the cerebellum, the cavum septum
pellucidum and insula.
Three-dimensional and four-dimensional ultrasound application in prenatal diagnosis
Fig. 14.3 In this fetal thorax, the cross-section volume acquisition in anterior–posterior
tomographic mode is used to demonstrate the slices of the heart, lungs, stomach,
diaphragm, etc. In the lower middle panel the bifurcation of the trachea is well seen.
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Ultrasound in obstetrics and gynaecology
Fig. 14.4 TUI can be used for the heart combined with STIC. Within one image mainly
moving structures can be seen.
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Once a volume data set of a fetal region is stored, the examiner can scroll
through the volume to get the plane of interest independent from the insonation
angle. In a STIC volume the reconstructed cardiac volume can be displayed in
the multiplanar or tomographic modes (Fig. 14.4), and played in slow motion or
stopped at any time for detailed analysis of specific phases of the cardiac cycle.
When combined with colour Doppler, events within the cardiac cycle during
systole and diastole can be very well demonstrated.
SURFACE MODE RENDERING
The image rendering of the fetal surface is the best known and most commonly
used display modality in 3D and 4D. From the volume acquired, the skin is primarily demonstrated (surface) and not the organs inside the body. It is used to
visualize the surface of a structure which is best achieved in the interlay between
fluid and surface, such as the face of a fetus in amniotic fluid or the valves within
the heart. The main advantage of the technique is its ease of use and its impact
on patients and doctors due to the lifelike image (Fig. 14.5), and comparison
with the postnatal appearance. Clinical applications include demonstration of the
whole fetus in the first trimester up to 12 weeks' gestation (see Fig. 14.5), and
demonstration of the face (Fig. 14.6), limbs, etc. in order to rule out or confirm
anomalies involving the skin as well as facial anomalies, spina bifida, limb anomalies and others. It is best demonstrated using 3D as well as 4D, whereas the latter
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Fig. 14.5 Surface mode demonstrating two fetuses at 10 weeks (left) and at 13 weeks.
Three-dimensional and four-dimensional ultrasound application in prenatal diagnosis
Fig. 14.6 With surface mode, maturation of the face and changes occurring during
pregnancy are well recognized. Three fetuses at 14 weeks (left), 26 weeks (middle) and
31 weeks (right).
can be used to analyse behaviour such as fetal movements, grimacing, yawning or
eye opening. Surface rendering can be applied to the fetal heart to visualize cardiac cavities and valves (Fig. 14.7). It can be used in the brain to demonstrate cavi-
ties such as the lateral ventricles, especially in the presence of brain anomalies.
MAXIMUM MODE RENDERING
This mode is used to highlight the maximal echo information of a volume data set
and is an ideal tool for the 3D reconstruction of bony structures (Fig. 14.8).6 In
general, cranial bones, the ribs and other curvilinear bones cannot be clearly seen
in a single 2D plane and are therefore better assessed in a maximum mode projection. This technique has been applied in the demonstration of spine and limb
abnormalities but was recently used in the assessment of the nasal bones, the cranial bones and corresponding sutures in normal and abnormal conditions.
technique delivers a picture similar to an x-ray of the bony skeleton in the fetus.
7–11
This
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