Atlas of Ultrasound Fusion Imagingin Obstetrics

The Fetal Brain and Placenta Accreta

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Atlas of Ultrasound Fusion Imagingin Obstetrics

The Fetal Brain and Placenta Accreta

Jean-Marc LEVAILLANT and Laurence GITZ

Catherine ADAMSBAUM and Stéphanie FRANCHI-ABELLA

Contributions by:

Bassam Haddad - Marie Victoire Senat - Claudine Touboul - Vanina Castaigne

Mathilde Gayet - Anne-Sophie Riteau - Frédéric Philippe - Edwige Hurteloup

www.livres-medicaux.com

THE AUTHORSJean-Marc LEVAILLANTCoordonnateur du DU d’Imagerie de la Femme (Paris XI)Echographiste référent du CPDPN de Créteil et de BicêtreCentre d’échographie – CEFFE - Créteil

Laurence GITZEchographiste référent du CPDPN de BicêtreService de Gynécologie Obstétrique – CHU BicêtreCentre d’échographie de l’Avancée – Antony

Catherine ADAMSBAUMProfesseur des UniversitésService de Radiopédiatrie – CHU Bicêtre

Stéphanie FRANCHI ABELLAService Radiopédiatrie - CHU Bicêtre

Contributions by:Bassam HADDADProfesseur des UniversitésService Gynécologie Obstétrique - CH Intercommunal – CréteilMarie Victoire SENATProfesseur des UniversitésService de Gynécologie Obstétrique - CHU BicêtreClaudine TOUBOULService Gynécologie Obstétrique - CH Intercommunal – CréteilVanina CASTAIGNEService Gynécologie Obstétrique - CH Intercommunal – Créteil

Mathilde GAYETService de Radiologie Générale – CHU BicêtreAnne Sophie RITEAU Service Gynécologie Obstétrique – CHU de NantesFrédéric PHILIPPEProduct Manager chez Hitachi-AlokaEdwige HURTELOUPAssistante du Dr Levaillant

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TABLE DES MATIèRES

PREFACE ............................................... 7TECHNIqUES (Frédéric Philippe) ................ 11Implementing ultrasound fusion imaging ................ 11Operational principles .............................................. 12Retrieval of the volume data .................................... 14Specific ultrasound equipment ................................ 16Overview of an installation ....................................... 20Limits to the work area............................................. 21Synchronization ........................................................ 22MRI sequences usable in obstetric-gynecological ultrasound fusion imaging ........................................ 26

THE FETAL BRAIN (Laurence Gitz, Jean-Marc Levaillant, Catherine Adamsbaum, Marie-Victoire Senat) .................................... 31The fetal Brain on ultrasound fusion imaging........... 31Ultrasound analysis of the fetal brain ....................... 31

Magnetic resonance analysis of the fetal brain ...... 33Fetal brain examination using fusion imaging .......... 34Cerebral anatomy ..................................................... 34Biometrics ................................................................ 35Study of myelination ................................................ 35Normal fetal brain on ultrasound fusion imaging ..... 35Key points in fusion imaging at 29 – 32 GA (weeks) 36Key points in fusion imaging at 33 – 37 GA (weeks) 38Examples of cerebral pathologies on ultrasound fusion imaging ................................... 53Midline anomalies: complete or partial agnesisof the corpus callosum ............................................. 53Ventricular dilatation ................................................ 57Vein of Galen aneurysmal malformations ................ 59Gyration anomalies .................................................. 64Posterior fossa anomalies ........................................ 67Bibliography .............................................................. 69

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THE PLACENTA (Laurence Gitz, Jean-Marc Levaillant, Anne-Sophie Riteau, Mathilde Gayet, Marie-Victoire Senat, Stéphanie Franchi-Abella) ....... 73The placenta on fusion imaging ............................... 73Technical aspects ...................................................... 73Semiological study .................................................... 82Intra-placental signs ................................................. 82Interface signs .......................................................... 82Vascularity anomalies in Doppler mode ................... 83Overall pseudo tumor aspects .................................. 83

Key points in the study of the placenta on ultrasound fusion imaging ................................... 84Technical aspects ...................................................... 84Signs grouped into four categories ........................... 84Two approaches to scoring currently being avaluated ....................................................... 85Normal placenta ....................................................... 86Placenta accreta ....................................................... 92Bibliography .............................................................. 99

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PREFACE

Ultrasound fusion imaging allows the real-time combination of previously acquired MRI data with ultrasound B-mode, Doppler and elastography images. This technique enables the ultrasonographer to take full advantage of the diagnostic power of both modalities at the same time.

The real-time ultrasound images are displayed simultaneously with the reconstructed MRI view.

This atlas represents three years’ work in collaboration with the specialist application engineers. Today, two atlases are being presented, one in gynecology and the other in fetal imaging.

We have endeavored to produce small books that cover difficult subjects but are easy to use.

In gynecology: cervical and endometrial cancer.

In fetal pathology: the brain and placenta accreta.

Other topics will follow in 2016:

• Ovarian masses and chronic endometriosis• The fetal thorax and abdomen.

The advances in our understanding of these technical applications were accomplished by a multidisciplinary group. Catherine Adamsbaum and Stéphanie Fanchi, pediatric radiologists at the Bicêtre Hospital in France, and Naima Chabi, radiologist at the Créteil Intercommunal Hospital Center, were our committed partners.

The dedicated gynecology and obstetrics teams at both the Bicêtre and Créteil hospitals enabled us to recruit eligible patients.

We also discovered that this technique was a powerful teaching tool for ultrasonographers, enabling them to refine their diagnostic precision in both MRI and ultrasound imaging.

8

These atlases have been realised thanks to Edwige Hurteloup, director of the Bicêtre 3D Ultrasound School, who undertook the assembly of the chapters with our texts and images.

We hope you will learn much from reading these atlases, in which we have honored the language of images.

Jean-Marc Levaillant et Laurence Gitz

PREFACE

TECHNIqUESFrédéric Philippe

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TECHNIqUES

ImplementIng ultrasound fusIon ImagIng

Image Fusion is a technique that allows current real-time ultrasound images to be combined with previously acquired MR/CT images.

All ultrasound modalities, such as color Doppler, power Doppler, eFlow, elastography, and even contrast ultrasound can be visualized during ultrasound fusion imaging.

VOLUME DATA SETMULTI-SLICE IMAGES

ULTRASOUNDIMAGE

CT

MRI

12

The most common imaging methods used for fusion are computed tomography (CT) and magnetic resonance (MR) images.

Presented for the first time during the 2003 RSNA under the name “Real-time Virtual Sonography (RVS),” the technique of merging ultrasound with CT multi-planar views was first described for radiology applications.

Fusion imaging used in this domain facilitates localization of hepatic and renal lesions, improving the precision and safety of interventions such as biopsies and radiofrequency ablation.

Thanks to advances in computing performance and simplified ergonomics, this technique can now be used for many new applications, including ultrasound fusion imaging in gynecology and obstetrics.

operatIonal prIncIples

The principle of operation consists of moving a cut plane simultaneously through two synchronized volumes.

The first volume is obtained via the reconstruction of a previously acquired CT or MRI data set. This is the “virtual” volume.

TECHNIqUES

13

The second volume consists of the zone of real-time ultrasound exploration.

Following synchronization of the two volumes, as the probe is moved, the corresponding view in the virtual volume will be displayed in real-time, side by side with the ultrasound image, no matter the orientation.

Reconstructed virtual volume Real-time ultrasound volume

Virtual volume Real-time volume Virtual volume Real-time volume

Synchronization Synchronization

TECHNIqUES

14

The probe is moved within the magnetic field generated by an emitter and a magnetic sensor clipped to the probe provides the information on its position and orientation at any time. This positional data is transmitted to the ultra-sound system to be processed together with the volume data.

retrIeval of the volume data

Ultrasound fusion imaging requires importation of CT or MRI data in DICOM format.

It is possible to use all types of CT and/or MRI sequences. Furthermore, these two modalities often provide comple-mentary information and can be used together in the same ultrasound fusion examination.

In gynecology and obstetrics, MRI data is generally used.

All or selected sequences can be imported via:

• CD/DVD recorded during the MR/CT examination• USB drive• A server (PACS or VNA) using a network connection and a Query/Retrieve DICOM transfer.

TECHNIqUES

15

The multi-slice sequences can be stored ahead of time on the ultrasound system hard disk to be used during a later session.

Each sequence will be converted into a 3-dimensional volume which will be the source of the multi-planar projec-tions displayed in real-time to correspond with the ultrasound image plane, once the 2 modalities have been synchronized.

TECHNIqUES

16

specIfIc ultrasound equIpment

The ultrasound platform must be equipped with an electronic 3D guiding system and specific software.

The movement of the ultrasound probe in space is analyzed via an electronic module which is connected to the ultrasound system. The module includes:

Processing unit

An antenna generates a close-range magnetic field

The emitter is attached to an articulated mobile support which can be locked in position.

TECHNIqUES

Control module

Magnetic sensorMagnetic field generator

Connection for magnetic field generator Connection for

movement sensor

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A magnetic position sensor

A holder for attachment

of the magnetic position sensor

TECHNIqUES

Magnetic sensor

Magnetic field generator

Wheeled support with articulated, multi-

directional arm

18

Each compatible ultrasound probe has a specific magnetic sensor holder. The sensor’s position is defined so as not to lose synchronization even when changing the probe during the procedure.

The mark on the magnetic sensor is used to determine its orientation when connected to the body of the probe.

It is particularly important to align the various reference marks on the probe, the sensor holder, and the sensor so that the probe’s movement is correlated with movement within the volume data set.

Assembly on an abdominal probe.

TECHNIqUES

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Assembly on an endovaginal probe

TECHNIqUES

Clip with sensor in positionOrientation

Sensor Attachment of sensor holder on the probe

20

overvIew of an InstallatIon

TECHNIqUES

21

lImIts to the work area

The ultrasound probe with the attached sensor must remain within the zone covered by the magnetic field, a zone extending from 20 to 76 cm from the emitter.

Outside of these limits, the virtual image could shake, due to weak signals from the position sensor.

The processing unit must remain at a minimum distance of 60 cm from the emitter to ensure that the magnetic field is not disturbed, which also could lead to a position sensor detection error.

TECHNIqUES

22

synchronIZatIon

When carrying out an ultrasound fusion imaging examination, the operator can import up to four different sequences and switch between them

At first it is necessary to define a reference axial, sagittal or coronal view in the virtual volume. This is the plane that will be acquired at the start of the ultrasound imaging and used to activate the registration between the two modalities.

When using several sequences simultaneously, it is also necessary to adjust the synchronization between the various virtual volumes.

3D navigational tools allow the translation and re-centering of the view.

Fine adjustment of the synchronization between two virtual volumes can be made by placing them side by side, and directly positioning an adjustment point on the same reference mark in each image.

TECHNIqUES

23

TECHNIqUES

The three virtual volumes must be synchronized before beginning the ultrasound examination.

Dividing the screen into four windows and using reference markers facilitates the procedure.

24

Launching and adjusting the synchronization

To launch the image fusion, one must acquire an ultrasound image in the same plane as that defined as the refe-rence plane in the virtual volumes and one must validate this position.

Two main methods allow the synchronization to be adjusted during the procedure:

Freezing one of the modalities while repositioning the other. It is generally the virtual image that is frozen to allow the operator to slightly modify the ultrasound view and then restart the image fusion.

TECHNIqUES

25

Note: To correct any adjustment errors, the previous registration parameters are automatically saved when the virtual image is frozen and can be recalled instantaneously.

Readjustment using reference points.

A first point is placed on a reference structure in the virtual image.

Marking the position of the same structure with a second point in the ultrasound image re-aligns the two planes.

TECHNIqUES

26

Mri sequences used in ostetric-gynecoLogicaL uLtrasound fusion IMAGING

All the various acquisition sequences can be imported and used in ultrasound fusion imaging, including T1, T2, Fat sat, Diffusion, 3D, etc.

A distinction should be made, however, between 2D sequences (axial, sagittal, coronal) and three-dimensional isotropic acquisitions.

Note: Where possible, it is preferable to have an extended acquisition, beyond the zone of immediate interest, which makes it easier for synchronization and ensures that you do not move outside the virtual volume with the ultrasound.

Isotropic three-dimensional acquisitions have the advantage of retaining an identical resolution in all planes. As a result, during ultrasound fusion imaging, the use of a single 3D MRI sequence is sufficient to obtain any view.

However, this type of acquisition is not routinely done in gyne-cology and could be difficult to obtain in obstetrics due to fetal movement.

2D slice acquisitions are the most commonly performed. They provide excellent spatial resolution as long as they are visualized in the acquired MRI plane.

MRI acquisition in the sagittal plane

TECHNIqUES

Image visualized in the MRI acquisition plane

27

Reconstruction from this type of sequence does not enable one to obtain isotropic volumes for virtual navigation.

In this case, rotating the ultrasound through 90° leads to a degraded reconstructed virtual (MRI) image.

MRI acquisition in the coronal plane

In ultrasound fusion imaging, it is necessary to use sequences in all the three planes—axial, sagittal and coronal—in order to maintain usable resolution within the virtual data no matter the orientation.

TECHNIqUES

Image visualized at 90° to the MRI acquisition plane

THE FETAL BRAINLaurence Gitz, Jean-Marc Levaillant,

Catherine Adamsbaum, Stéphanie Franchi-Abella, Marie-Victoire Senat

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THE FETAL BRAIN ON ULTRASOUND FUSION IMAGINGUsing fusion imaging to study the fetal brain has the primary advantage of combining MRI and ultrasound data

that is synchronized and focused on the specific zone of interest. The imaging technique is therefore an excellent teaching tool for the study of the normal brain, both in initial and ongoing training, and it combines the advan-tages of both types of imaging for the study of pathological cases. Indeed, fusion imaging enables one to pinpoint anatomic structures and describe them using this two-fold semiology. The synchronization of the views brings to light structures reputed to be difficult to find or to interpret by one technique thanks to the second, and vice versa.

We will first review the contributions and limitations of each technique, the limitations of one often being over-come by the advantages of the other.

ultrasound analysIs of the fetal braIn

Advantages of fetal brain ultrasound

Spatial resolutionWith advances in equipment and probes, fetal brain ultrasound imaging now offers very good spatial resolution,

often down to millimetric precision. Ultrasound enables good interpretation of cerebral structures due to the nume-rous ultrasound interfaces between the cerebral tissue and the pericerebral and ventricular spaces. Fetal mobility helps the operator, who can mobilize the fetus to be able to direct the ultrasound in the plane that offers the optimal acoustic window.

THE FETAL BRAIN

32

Study of cerebral vascularityUse of the pulsed, power and color Doppler modes help significantly in diagnosing vascular anomalies and moni-

toring cerebral vascular resistance and cerebral blood flow velocity when there is retarded growth or when a fetus is at risk of anemia.

the limitations of fetal brain ultrasound

Bony plates and pericerebral spacesThe ultrasound undergoes significant attenuation passing through the bony plates, particularly during the third

trimester as bone density increases. This considerably reduces the ultrasound information captured.

Furthermore, the study of the proximal hemisphere is very limited. Similarly, the study of the gyri is limited by the difficulty of obtaining an ultrasound window through the fontanelle or bony sutures. The narrowness of the pericerebral space adds to the reverberations of the cranial vault, constituting another limitation to the study of the cortical gyration.

The study of myelinationMyelination, the final phase of cerebral development, is accompanied by an increase in lipids and protein and a

decrease in water in the white matter. These modifications are not visible by ultrasound, and yet the study of myeli-nation proves to be important in the prognosis of certain pathologies, such as the effects of vascular malformations on the parenchyma.

THE FETAL BRAIN

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magnetIc resonance analysIs of the fetal braIn

Advantages of MRI

Multiple sequencesSingle-shot fast spin echo (SSFSE) sequences are the most frequently used for fetal brain imaging. These acquisi-

tions limit the impact of fetal movements on the quality of the images. T2 sequences offer good contrast between the LCR and the brain tissue and are used to study both the brain surface and the ventricular structures. These sequences are complemented by acquisitions in T1 mode in order to detect hemorrhage and fat signals, for example, or to pinpoint the pituitary stalk as a hyperintense T1 signal. T1 weighting is also particularly well adapted to highli-ghting myelination. Other sequences could be performed to complete the examination: fluid attenuation inversion recovery (FLAIR), diffusion and echoplanar imaging (EPI).

Multiplanar studyExamination of the fetal brain is done in three planes (sagittal, coronal and transversal). The interpretation of

the reference plane is by using biometric and anatomic criteria to compare to the norms established by numerous teams and published in the literature (C. Garel et al., C Adamsbaum et al.).

the limitations of Mri

Fetal mobilityAs the technology progresses, sequence acquisition time is being reduced. Nonetheless, fetal movement can still

often create artifacts. This can have a real impact on spatial resolution and biometrics.

THE FETAL BRAIN

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fetal braIn examInatIon usIng fusIon ImagIng

Ultrasound fusion combines the advantages of both MRI and ultrasound. It enables a combined, synchronized, focused study of cerebral structures with the help of double semiology with or without the use of Doppler.

cerebral anatomyAnatomical study allows:

• Assessment of gyration depending on the gestational age• The presence and characteristics of the main sulci and gyri of the internal side of the hemispheres (cingulate,

marginal, paracollicus sulcus; internal parieto-occipital and calcarine fissure), on the inferior side (collateral and external occipito-temporal and hippocampal fissure), the external side (frontal, temporal intraparietal sulci) and the convexity sulci (central, pre and post-central)

• The study of the operculation of the sylvian fissure• Study of the basal ganglia, thalamus, and germ layers• The study of pericerebral fluid spaces, the septum, the lateral ventricles, the 3rd and 4th ventricles, the Aqueduct

of Sylvius, the cisterna magna• Study of the mesencephalon, colliculi, peduncles, tegmentum, pons

• Study of the posterior fossa, the cerebral hemispheres, vermis, fissures, axis, tent .• Study of the midline, corpus callosum

THE FETAL BRAIN

35

Biometric parametersA biometric study includes biparietal diameter, head circumference, fronto-occipital diameter, bony biparietal

diameter, cerebral biparietal diameter, length and thickness of the corpus callosum, the lateral ventricles, the third ventricle, the fourth ventricle, the cisterna magna, the inter-hemispheric distance, the inter-ocular distance, the height and anteroposterior diameter of the vermis, the vermis surface area, the transverse diameter of the cere-bellum. Each measurement must use the precise measuring method described in the biometric references used in ultrasound and in MRI.

study of myelinationThis is best done with T1 weighted images. On a transverse slice through the fourth ventricle, there is a hyperin-

tense signal at the level of the protuberance, in the vermis and the middle cerebellar penduncles. This signal is defined as being inferior or equal in intensity to the cortex, and superior to the white matter in the oval center.

normal fetal braIn on ultrasound fusIon ImagIngThis atlas sets out to present fusion imaging with the aid of a check list of the essential points and illustrated with

clinical images.

All of the cases presented correspond to fetuses with a gestational age greater than 29 weeks. Fetal cerebral MRI has little use before that gestational age.

We have chosen to present the images as they appear on the screen of the ultrasound fusion imaging platform without modifying their spatial orientation. Fusion imaging is performed in the plane that is most accessible to the ultrasound beam.

THE FETAL BRAIN

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Key points in fusion iMaging at 29 – 32 ga (weeKs)• gyration: primary fissures in place

• Frontal and parietal lobes- Pars marginalis, precentral and postcentral sulci, superior frontal sulcus is always visible at 29 weeks GA,

central sulcus is visible at depth - Inferior frontal sulcus is always visible at 30 weeks.

• Insula being covered progressively: posterior closing of the Sylvian fissure• Frontal lobe covering the posterior end of the insula

- The frontal lobe must cover half of the posterior end between 29 and 31 weeks• Temporal lobe

- The front part of the superior temporal sulcus is completed (32 weeks)- The inferior temporal sulcus is visible at 30 weeks

• Parenchyma• Sustentorial myelination beginning: posterior arms of the internal capsules.• Homogenous; “layers”* disappear

• Midline• Study of the anterior complex: inter-hemispheric fissure, paricollicus sulcus, the corpus callosum (hypointense

T2 signal), the septal cavity or septum pellucidum separating the anterior horns.

* Groups of residual glial cells can be observed around the anterior horns in the form of a hypointense T2 signal (Girard et al, 2001)

THE FETAL BRAIN

37

• Ventricles• Atrial diameter less than 10mm

- The measurement is performed using the ultrasound technique, in a true axial plane passing through the ventricular atrium, perpendicular to the plexus, without including the ventricular wall itself.

• Subarachnoid spaces• Still wide, particularly in the posterior regions

• Posterior fossa• Brain stem: posterior myelination (tegmentum and ascending fibers)• Cerebellum

- Primary foliation visible at the level of the vermis- Myelination of the cerebellar peduncles and of the white matter

• Identification of the retrocerebellar cisterna magna• Two symmetric hemispheres• Hyperechoic vermis• 4th ventricle triangular, point to the front

THE FETAL BRAIN

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Key points in fusion iMaging at 33 – 37 ga (weeKs)

• Gyration: primary fissures in place• Development of numerous secondary and tertiary sulci, difficult to analyze (individual variations; not as deep

as primary sulci).• Sylvian fissures close laterally, progressively until term• All the temporal sulci should be visible (superior temporal, inferior temporal, temporo-occipital and collateral)

starting at 33 weeks• Back end of the insula covered by the frontal lobe

- The frontal lobe should cover the posterior end fully at 32 weeks

• Parenchyma• Myelination progressing: upper arms of the internal capsules and the pallidum, starting at 33 weeks gestation;

optic radiation and subcortical white matter in the central region, starting at 35 weeks

• Midline• Study of the anterior complex: inter-hemispheric fissure, paricollicus sulcus, the corpus callosum (hypointense

T2 signal), the septal cavity or septum pellucidum separating the anterior horns.

• Ventricles• Atrial diameter less than 10mm

THE FETAL BRAIN

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- The measurement is performed using the ultrasound technique, in a true axial plane passing through the ventricular atrium, perpendicular to the plexus, without including the ventricular wall itself.

• Subarachnoid spaces thin

• Posterior fossa• Growth of cerebellum in three spatial planes; good visibility of the primary fissure, other fissures not very deep• Progression of myelination

- Brain stem: dorsal ascending fibers- Cerebellum: cerebellar peduncles, vermis and hemispheres

• Identification of the retrocerebellar cisterna magna• Two symmetrical hemispheres• Hyperechoic vermis• 4th ventricle triangular, point to the front

THE FETAL BRAIN

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normal fetal brain – sagittal view

sagittal view at 31 weeks ga

THE FETAL BRAIN

Cingulate sulcus

Tegmentum

Pons curvature

Cisterna magna

Cerebellar tent

Corpus callosum

ColliculiAcqueduct of SylviusMedulla oblongata junction

Corpus callosum

Cavum of the septum pellucidum

Fornix

Primary vermis fissure

4th ventricle

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parasagittal view passing through the thalamus at 31 weeks ga.

THE FETAL BRAIN

Central sulcus

Precentral sulcus

Postcentral sulcus

Intersection of ventricles

Cerebellar hemisphere

Occipital cortex

Thalamus

Ventricular intersection

Cisterna magna

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parasagittal view passing through the parieto-occipital fissure at 31 weeks ga

THE FETAL BRAIN

Postcentral sulcus

Lateral ventricle

Central sulcus

Parieto-occipitalfissure

Temporal cortex

Cerebellarhemisphere

Calcarine fissure

Thalamus

Perieto-occipital fissure

Calcarine

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sagittal view passing through the corpus callosum at 31 weeks ga – color doppler

THE FETAL BRAIN

Frontal midline rami

Superior sagittal sinus

Callosomarginal artery

Pericallous artery

Vein of Galen

Right sinus

Basilar trunck

Anterior cerebral artery

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Frontal view of normal fetal brain

frontal view passing through the cerebral peduncles and the pons at 31 weeks ga

- seen from the front.

THE FETAL BRAIN

Cavum of the septumpellucidum

3rd ventricle

4th ventricle

Cisterna magna

Pons

Spinal cord

Frontal horn of lateral ventricles

Cingulate sulcusCorpus callosum

Sylvian fissure

Cerebellum peduncles

Collateral sulcus

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frontal view passing through the anterior complex and the posterior fossa at 31 weeks ga

– seen from the side.

THE FETAL BRAIN

3rd ventricle

Cingulate sulcus

Precentral sulcus

Sylvian fissure

Acqueduct of Sylvius

Corpus callosum

Cavity of theseptum pellucidum

Frontal horn of lateralventricle

Acqueduct of Sylvius

4th ventricle

Fornix pillars

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frontal view passing through the aqueduct of sylvius at 31 weeks ga

THE FETAL BRAIN

Acqueduct of Sylvius

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frontal view with doppler at 31 weeks ga

THE FETAL BRAIN

Superior temporal sulcus

Inner ear

Thalamostriate artery

Callosomarginal artery

Pericallous artery

Anterior cerebral artery

Internal carotid artery

Basilar trunk

Vertebral artery

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frontal view with doppler at 31 weeks ga – vascularization of the nuclei cerebelli

THE FETAL BRAIN

Caudate nucleus

Lentiform nucleus

Thalamus

Thalamostriate artery

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Cerveau fœtal normal en coupe axiale

axial view, section, through the pc, at 31 weeks ga

THE FETAL BRAIN

Thalamus

Lentiform nucleus

Head of caudate nucleus

Cavity of septum pellucidum

3rd ventricle

Sylvian fissure

Temporal sulcus

Anterio occipital sulcus

Lateral occipital sulcus

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posterior axial view at 31 weeks ga

THE FETAL BRAIN

Calcarine fissure

Lateral occipital sulcus

Occipital lateral ventricular horn

Occipital cortex

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axial view passing through the posterior ventricular intersection at 31 weeks ga

THE FETAL BRAIN

Cingulate sulcus

Ventricular intersection

Anterior occipital sulcus

Collateral sulcus

Ventricular wall

Choroid plexus

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axial view passing through the circle of willis

THE FETAL BRAIN

Superior cerbellar peduncle

Cerebral peduncle

Optic chiasma

Posterior cerebral artery

Mid cerebral artery

Anterior cerbral artery

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ExAMPLES OF CEREBRAL PATHOLOGIES ON ULTRASOUND FUSION IMAGINGmIdlIne anomalIes: complete or partIal agenesIs of the corpus callosum

The diagnosis of complete or partial agenesis of the corpus callosum (ACC) is based on both direct ultrasound signs (absence of visualization of the corpus callosum) and indirect signs (absence of septum pellucidum cavity, eleva-tion of the 3rd ventricle, parallel lateral ventricles, bull’s-horn aspect of the frontal horns, colpocephaly and radial splaying of the internal hemisphere sulci).

In partial agenesis of the corpus callosum, the corpus callosum measurements are lower than normal and one of the parts of the corpus callosum could be missing. There could also be callous dystrophy by hypoplasia, or a corpus callosum that is abnormally thick.

An ultrasound examination allows more precise biometric measurements than those done on the MRI by way of a true trans-fontanelle sagittal view without partial volume effects, which gives good spatial resolution. The operator will also look for a hyperechoic addition (lipoma) or anechoic sign (cyst) on the midline, which could be associated with callous dysgenesis. The standard ultrasound examination is a necessary addition when looking for intra- and extra-cerebral anomalies.

The MRI finds the same signs as the ultrasound. The posterior part of the corpus callosum, which is sometimes hard to capture on ultrasound, is accessible on the MRI. The MRI is particularly useful in looking for associated anomalies (gyration, myelination, posterior fossa and pons).

Advantages of fusion imaging : The use of fusion imaging makes it possible to combine a two-fold, synchronized, focused semiology. The MRI can be limited due to acquisition difficulties, fetal movement, and maternal brea-thing. There is the risk of errors in interpretation when a partial volume effect could modify the anatomical and biometric parameters of the corpus callosum. Use of fusion imaging reduces these risks and corrects the measu-rements made with MRI alone, thanks to the possible verification of doubtful anatomic structures by using the ultrasound fusion imaging.

THE FETAL BRAIN

54

complete agenesis of the corpus callosum at 33 weeks ga

axial view – disorganization of the anterior complex

THE FETAL BRAIN

Colpocephaly

Thalamus

Elevation of 3rd

ventricle

False image of the cavum

by the ascension of 3rd ventricle

Vertical, thinned aspect to the frontal horns abnormally splayed with a «bull’s horn»

55

complete agenesis of the corpus callosum at 33 weeks ga

Posterior frontal view – from the side

Colpocephaly: disparity in caliber between the large ventricular intersections

and the thin frontal horns (cf. previous illustration).

THE FETAL BRAIN

Dilated ventricles

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short corpus callosum at 32 weeks ga

Sagittal view coupled with power Doppler (lower image)

THE FETAL BRAIN

Marginal sulcus

Cingulate sulcus

Small septum pellucidum cavum

Parieto-occipitalfissure

Short corpus callosum

Atypical path of pericallous artery

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ventrIcular dIlatatIon

The diagnosis is made from the ultrasound: one should explore ventriculomegaly whenever the choroid plexi do not fully occupy the ventricular intersections, and to confirm it with the adapted measurement of the lateral ventricles. In this case, it is recommended to measure the width of the lateral ventricular intersection on the true axial view, tangentially to the choroid plexus and perpendicular to the ventricular wall. The measurement should only involve the internal fluid component, and not the walls.

Ventriculomegaly is defined by a measurement greater than 10 mm, that can be unilateral or bilateral.

In such cases, specific morphological examination for ventriculomegaly should be performed, including the lateral ventricles, the 3rd and 4th ventricles, the form of the ventricles and the aspect of the walls. Analysis of the central nervous system integrating the cerebral organization: posterior fossa, midline, subtentorial level, eye, rachis and spinal cord, should be included.

A study of cerebral maturity should be made (cerebral biometric parameters and gyration).

A study of cerebral morphology will find malformations associated with ventriculomegaly, such as Dandy-Walker malformation, stenosis of the Aqueduct of Sylvius, agenesis of the corpus callosum, lissencephaly, arachnoid cysts, vascular malformations and intracranial tumors.

Functional cerebral pathologies could also lead to ventricular dilation, primarily represented by intraventricular hemorrhage and anoxo-ischemic lesions of the porencephalon or periventricular leucomalacia.

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advantages of fusion imaging : Fusion imaging is particularly interesting in all its associated forms because it allows the simultaneous interpretation of MRI and ultrasound signs. Ventricular wall definition is best seen on ultrasound, which can demonstrate regular or crenelated, thickened, or hyperechoic walls, for example, along with the contents of the ventricles. In comparison, the analysis of the parenchyma is more detailed on MRI, which can show heterotopia, porencephaly, and sub-ependymal cysts, for example. Fusion imaging makes the synchro-nization of this double semiology for a specific zone possible.

Bilateral ventricular dilation of 11 mm, isolated, at 33 weeks ga

Axial view passing through the ventricular intersection

Note the visualization of the basal ganglia and the venous sinuses.

THE FETAL BRAIN

Head of the caudate nuclei

Lentiform nuclei

Thalamus

Superior sagittal sinus

Right sinus

3rd ventricle

Cavity of septum pellucidum

Frontal horn

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veIn of galen aneurysmal malformatIon

Vein of Galen aneurysmal malformation (VGAM) is a congenital vascular malformation characterized by the dila-tion of an embryonic precursor of the vein of Galen secondary to various arteriovenous malformations.

The vein of Galen connects the deep venous system with the right sinus and the torcula (or confluence of sinuses). It can be diagnosed prenatally when there is precocious vein dilation. It is visible on ultrasound as an anechoic oblong form located behind and under the thalami, above the cerebellum tent, midline, beginning under the tail of the corpus callosum and descending to the bony table at the level of the confluence of the sinus. This vein dilatation is visible in the three planes during an ultrasound examination, but when it is small in size, it may not be visible on the BPD/HC axial view.

Using the Doppler mode, the malformation appears with intense turbulent vascular flow.

The fetal examination will assess the impact of the malformation on the cardiac and brain systems. An MRI enables assessment of the consequences for the cerebral parenchyma.

Abnormal signs related to the cerebral parenchyma (edema, differentiation, myelination anomalies, and even porencephaly) result from the brain tissue suffering from arteriovenous circulatory limitations.

advantages of fusion imaging: Fusion imaging makes it possible to couple vascular signs identified in the Doppler mode, with parenchymal lesions found on MRI. Working with various MRI sequences, notably diffusion-weighted, this imaging can improve the understanding of the natural history of the aneurysmal malformations, their progres-sion, and their consequences for the parenchyma. Fusion imaging also enables more advanced ultrasound identi-fication of the abnormal parenchymal zones and the development of a specific ultrasound semiology.

THE FETAL BRAIN

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Vein of galen aneurysmal malformation at 33 weeks ga. Axial view passing through the dilated vein –power Doppler (upper window) with overall differentiation between white /grey matter.

THE FETAL BRAIN

Transverse sinus

Vein of Galen

Right sinusVeine de Galien

Torcula

Vascular network upstream of fistula

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Vein of galen aneurysmal malformation at 33 weeks ga.

Sagittal view passing through the dilated vein.

THE FETAL BRAIN

Dilatation of Galen bulb

Right sinus

Cerebellum tent

Torcula

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Vein of galen aneurysmal malformation at 33 weeks ga.

Frontal view passing through the dilated vein.

THE FETAL BRAIN

Dilatation of Galen bulb linked to upstream anteriovenous fistula

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Vein of galen aneurysmal malfor-mation at 33 weeks ga, second case.

Sagittal view above and axial view below, passing through the dilated vein.

Cerebral parenchyma signal and volume anomalies on MRI with differentiation of white / grey matter (encephalomalacia).

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gyratIon anomalIesDelayed gyration or lissencephaly type anomalies are among serious brain development abnormalities and are

generally diagnosed using MRI.

advantages of fusion imaging: Fusion imaging provides additional arguments to encourage and develop the study of gyration and its anomalies with ultrasound. It is a good tool for learning to pinpoint normal fissures and sulci based on gestational age, both in initial training and continuing education. This enables the further study of gyra-tion with ultrasound and a better understanding of the ultrasound windows that enable this analysis.

gyration anomaly at 29 weeks ga. Axial view. Note the visualization of the sulci on ultrasound in the distal hemisphere. Abnormal gyration, retarded for gestational age, sulci discordant and asymmetric.

THE FETAL BRAIN

Postcentral sulcus

Central sulcus

Precentral sulcus

Parieto-occipital fissure

Abnormal sulcus

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gyration anomaly at 29 weeks ga. Frontal view passing through cerebellar pedoncles. Asymmetric gyration retarded for GA.

THE FETAL BRAIN

Asymmetric Sylvian fissure

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gyration anomaly at 30 weeks – axial view passing through the occipital horns.

Overall lissencephaly associated with open non-operculated Sylvian fissures in relation to gestational age, associated with partial agenesis of the corpus callosum.

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posterIor fossa anomalIes

Ultrasound exploration of the posterior fossa includes the analysis of the pericerebellar spaces called the cisterna magna.

The latter is measured on ultrasound by the distance between the posterior edge of the vermis and the anterior edge of the occipital shell, on an axial view passing through the cerebellum.

When it is greater than 10mm, it is referred to as mega cisterna magna. The enlargement of this space could also correspond to a retro-cerebellum cyst or a vermis hypoplasia. The aspect and biometric parameters of the vermis and cerebellum are needed to explore these anomalies, as is the position of the cerebellum tent and the shape of the fourth ventricle, all criteria needed to make a diagnosis and prognosis.

A full study at the supertentorial level is also needed.

Advantages of fusion imaging: Once again, fusion imaging offers two-fold synchronized and focused semiology, which serves both as a good learning tool to pinpoint the anatomic structures of the posterior fossa, and also as an aid for interpreting and confirming abnormal structures. It enables ultrasound operators to improve their inter-pretation in order to contribute to the MRI semiology, to enable views of structures that are sometimes reputed to be inaccessible with ultrasound, but that can be seen by modifying the ultrasound access window and by using indirect, vascular or fluid, reference points. Fusion imaging also enables one to understand the difficulties of inter-preting images and taking biometric measurements in the presence of partial volume and movement artefacts. Yet, finding certain structures and measuring them are crucial to establishing a prognosis of certain anomalies of the posterior fossa (vermis, pons).

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Enlargement of cisterna magna at 34 weeks GA. Sagittal views passing through the vermis, on the lower image with power Doppler. Enlargement of the cisterna magna, height of the vermis at 3rd percentile, with very little curvature of the pons, tent in place.

THE FETAL BRAIN

Curvature of pons

Cisterna magna

Cerebellum tent

Right sinus

Primary fissure of vermis

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Bibliography

Guibaud L. Contribution of fetal cerebral MRI for diagnosis of structural anomalies. Prenat Diagn 2009; 29: 420–433

Quarello E, Stirnemann J, Ville Y, Guibaud L. Assessment of the sylvian fissure development between 22 to 32 weeks of gestation. Ultrasound Obst Gynecol 2008

Bondiaux E, Garel C. Fetal Cerebral Imaging Ultrasound vs IRM : an update. Acta Radiolo 2013 : 54 : 1046 – 1054

Garel C. Atlas IRM cérébral : le développement du cerveau fœtal. Sauramps Médical. Montpellier 20000

Adamsbaun C, Gelot A, André C. Atlas d’IRM du cerveau fœtal : guide d’interprétation des aspects normaux. JM Baron Masson 2001

Bault JP, Coquel P, Ville Y. Pratique de l’échographie obstétricale au deuxième et au troisième trimestre. Sauramps Médical 2009

THE FETAL BRAIN

THE PLACENTALaurence Gitz, Jean-Marc Levaillant,

Anne-Sophie Riteau, Mathilde Gayet,

Marie-Victoire Senat, Stéphanie Franchi-Abella

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THE PLACENTA ON FUSION IMAGING

Fusion imaging is a useful addition to the diagnostic toolbox for placenta implantation anomalies. This examination improves the reading of signs for placenta accreta by coupling two complementary semiologies, synchronized and focused on the suspicious area.

Fusion imaging can include a study of vasculature using Doppler, synchronized with MRI sequences.

This semiological analysis presents another advantage: by definition, the imaging is dynamic, allowing one to return as often as required to the suspicious area.

We know that in practice there is often differences between ultrasound and MRI conclusions. Fusion imaging helps to understand the reasons for these differences by reviewing the signs present on ultrasound and absent on MRI, and vice versa. It is possible to determine, using the approach proposed here, for which category of signs there is disagreement. Thus, using the double semiology during fusion imaging, which is now synchronized and dynamic, it is easier to confirm or refute the pathological nature of these signs.

The cases presented in this atlas relate to placentae in patients with a uterine scar, all the cases related to a previous cesarean section, with the exception of one patient who had a complete cure for synechia and who had a suspicious looking placenta on ultrasound. All the patients had an MRI after 32 weeks GA.

We now believe that it could be interesting to do the MRI earlier. Analysis done earlier would make it possible to study the placenta/myometrium interface, which, after 32 weeks is more difficult as extension of the inferior segment sometimes thins the scar for reasons not at all related to the accretion of the placenta.

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Ultrasound fusion imaging combines vascular information provided by the Doppler mode with MRI images. This technique could reduce the need to inject gadolinium. Currently, the use of gadolinium is not systematic, and the relation of risk/benefit is controversial. Furthermore, an angioMRI could provide useful information about vascular networks to aid the embolization team’s involvement later. AngioMRI can also be used to look for rare but serious posterior vascular invasion in cases of posterior placenta percreta. Ultrasound fusion imaging does not help in making decisions related to the posterior vascular network.

First, we will look at the ultrasound fusion techniques that are specific to the placenta, and then we will present an analysis of placenta accreta signs.

Here, we develop a new semiological approach, looking to group together already known signs into four catego-ries. This new approach is also adapted for the analysis of the placenta on ultrasound and MRI alone, but use of this model in fusion imaging provides two scores, qualitative and quantitative, contributing to diagnosis and prognosis.

It is nevertheless necessary to remember that there is currently no examination or sign that enables an absolute diagnosis of placenta accreta. Results from publications from many teams have shown:

• The limitations in sensitivity and specificity of each technique• A limited number of cases, considerably reducing the statistical value of these cases.

As a result, we must remain vigilant when caring for patients with a myometrial scar.

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technIcal aspects

Ultrasound fusion imaging has few technical constraints. It requires that a maternal MRI be performed previously. The current protocol in our center is using a Siemens 1.5 T MRI, “fast” T2-weighted sequences (True FISP©) and “single shot” (HASTE©) in sagittal views to first localize the placenta and the bladder-uterine interface. Then rapid and single shot T2 sequences are done in the oblique coronal plane, or perpendicular to the bladder-uterine inter-face. An injection of gadolinium is given with an angioMRI abdominal-pelvic arterial sequence, followed by volume interpreted gradient echo (VIBE©) T1 acquisition in sagittal and oblique coronal views.

After the MRI, the patient goes to ultrasound, where the MRI sequences are transferred to the ultrasound fusion platform for Real-time Virtual Sonography (RVS). All types of sequences can be used for the fusion imaging (Fig. 1).

The mother should have a full bladder and the filling should be identical for both MRI and ultrasound fusion acqui-sition (Fig. 2).

Synchronization is done using independent reference points related to the fetus, cord insertion and internal cervical orifice, with verification of the lateral synchronization from the lateral margins of the uterus (Fig. 3).

Fusion imaging can be used with either abdominal or vaginal scanning. One simply needs to place the RVS sensor on the chosen probe (Fig. 4).

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fig. 1: Use of variously weighted MRI images.

THE PLACENTA

Left: T2-weighted MRI sequence (the most useful)

Right: T1-weighted MRI (bottom right: after gadolinium injection)

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fig. 2: adapt bladder filling during fusion imaging to that during Mri.

Left: empty bladder during fusion imaging. Right: full bladder during fusion imaging.

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fig. 3: Synchronization of images.

The synchronization of images using the cervical canal (arrow): finding reference points at the internal and external orifices of the cervix on both ultrasound and MRI.

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fig. 3 (con’t): synchronization of images.

Synchronization with cord insertion (arrow)

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fig. 4: several ways to start the fusion imaging.

Fusion using the transabdominal approach

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fig. 4 (con’t): several ways to start the fusion imaging.

Fusion using the vaginal transducer.

Note that the presentation will lower at the time of fusion.

THE PLACENTA

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sémIologIcal study

An ultrasound fusion examination should look for four categories of signs: intra-placental anomalies, myome-trium/serous/adjacent organ interface anomalies, vascular anomalies, and the overall aspect of the placenta.

Intra-placental signsThe presence of intra-placental lacunae in relation to the accreta zone. These lacunae are physiologically frequent

during the third trimester, and as a result, it is necessary to define them more precisely based on their number, aspect and size. The more numerous they are, very small or very large and irregular, the more suspicious they are. These irregular lacunae, either small or very large, are more linear than rounded, with smooth edges, without a hyperintense border signal, unlike venous lakes. They are not necessarily located opposite the placental invasion zone. In Doppler mode, there is turbulent flow inside them. They are enhanced after injection.

• Black, intra-placental bands, with hypointense T2 signal, correspond to fibrin deposits.• T2 signal intensity is heterogeneous for the placenta.

Interface signs• The absence of a hypoechoic border between the placenta and the myometrium. This is a classic sign for the

diagnosis of placenta accreta. This hypoechoic border represents the decidua, which is missing in cases of placenta accreta.

• Interruption of the hyperechoic zone between the uterine serous membrane and the bladder wall. The border between the bladder and the myometrium is normally hyperechoic and smooth. In cases of placenta accreta, this hyperechoic line can be interrupted or domed towards the bladder.

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• A myometrium less than 1 mm thick or virtually disappeared would suggest placenta accreta.• Sometimes, there are direct signs of invasion of the uterine serous membrane or adjacent organs, notably the

bladder. This could be a modification of the bladder-uterine wall with visualization of tissue or vessels invading the bladder and making the wall irregular.

• Loss of the “three layer” MRI: three layers- placental interface/myometrium, hyperintense border signals for the myometrium, hypointense signal between the myometrium and the bladder serous membrane.

• Extension of the placental tissue to adjacent organs, notably the bladder, with hyperintense T2 signal.

Vascularity anomalies in doppler mode• Unusual aspect of subchorionic vascularity, which is very dense with vessels that are perpendicular to the chorionic

plate. Normally the vascular network runs along the chorionic plate and some vessels dive into the placenta, in cases of placental insertion anomalies this network is disorganized, presenting numerous perpendicular vessels sometimes jutting right into the canal in voluminous lacunae.

Overall pseudo tumoral aspects• Very heterogeneous pseudo tumor• Abnormal doming of the inferior segment towards the front

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KEY POINTS IN THE STUDY OF THE PLACENTA ON ULTRASOUND FUSION IMAGING

technIcal aspects:

• Full bladder on MRI and fusion• Single shot T2 MRI sequence (HASTE©)• Synchronization with cord insertion and cervical canal• Abdominal or endovaginal probe

sIgns grouped Into four categorIes

THE PLACENTA

• A = Intraplacental anomalies• Lacunae > 4, very small or very large, irregular• Black bands with hypointense T2 signal > 4• Clear heterogeneity of intraplacental signal

• B= Interface anomalies• Thin myometrium• Loss of hypoechoic border• Loss of three-layer aspect• Interruption of serous membrane

• C = vascularity anomalies on Doppler• Disorganized and dense vascularity• Loss of usual horizontal sub chorionic aspect

• D = overall aspect• Doming• Pseudo-tumoral

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two approaches to scorIng currently beIng evaluated

Qualitative score The association of category A + B represents a strong risk of accreta.

The association of A or B+C: intermediate risk

If neither A, nor B: low risk

Quantitative scoreIn categories A, B and D, when the signs are only present on one of the techniques we score it with 1 point, when

present on the two techniques, we score it with 3 points.

Category C is scored as 1 point.

There is a maximum score of 10 points.

The higher the score, the greater the risk.

Beyond a threshold equal to or greater than 4, the patient is considered high risk.

These scores are currently under evaluation. The question of the diagnostic value of a sign or an examination that assesses placental insertion always raises the issue of the number of cases and their statistical value. A study of this scoring system should be published shortly by the Bicêtre-Créteil teams.

For each examination present in this atlas, the captions describe the visible signs and classify them in categories A, B, C, and D.

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NORMAL PLACENTA

THE PLACENTA

sagittal viewA: Few lacunae, few bandsB: three layers, myometrium respectedC: usual vascular aspect

D: usual domingQualitative score: low riskQuantitative score: 0Definitive diagnosis: placenta non accreta

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THE PLACENTA

Axial viewA: Few lacunae, few bandsB: doubt concerning the integrity of the posterior myometrium on MRI, myometrium respected on ultrasound

C: vascularity without abnormalities (not presented)D: no unusual domingQualitative score: moderate riskQuantitative score: 1Definitive diagnosis: placenta non accreta

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THE PLACENTA

sagittal viewA: Absence of bands and lacunaeB: Myometrium respectedC: Usual vascularityD: Overall aspect showing no particularitiesQualitative score: low riskQuantitative score: 0Definitive diagnosis: placenta non accreta

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THE PLACENTA

sagittal viewA: Few lacunae, regularB: Thin myometriumC: Usual vascularity

D: Overall aspect showing no particularitiesQualitative score: moderate riskQuantitative score: 3Definitive diagnosis: placenta non accreta

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THE PLACENTA

Right lateral axial viewA: Few lacunae, few bandsB: Myometrium thin and hard to followC: Significant retro-placental vascularityD: Usual overall aspectQualitative score: moderate riskQuantitative score: 4Definitive diagnosis: placenta non accreta

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THE PLACENTA

sagittal viewA: Few lacunae, numerous bandsB: Myometrium – placenta interface respectedC: Usual vascularity

D: Usual overall aspectQualitative score: moderate riskQuantitative score: 1Definitive diagnosis: placenta non accreta

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THE PLACENTA

ACCRETA PLACENTA

Right lateral axial viewA: Large irregular lacunae and bandsB: Myometrium thin and hard to follow (*)C: Vascularity presented on figures that follow. Major retroplacental vascularity with large vessels in the lacunae.D: Unusual overall aspectQualitative score: high risk (A+B)Quantitative score: 10Definitive diagnosis: placenta accreta

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THE PLACENTA

Right lateral axial viewA: Large irregular lacunae and bandsB: Neovasculature replacing myometrium that is thin and hard to follow (*)C: Major retroplacental vascularity with large vessels in the lacunae.D: Unusual overall aspectQualitative score: high risk (A+B)Quantitative score: 10Definitive diagnosis: placenta accreta

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THE PLACENTA

Axial viewA: Heterogeneous placenta, large irregular lacunaeB: Placental-myometrium interface poorly delimitedC: Typical vascularity (not shown)D: Pseudo-tumoral aspectQualitative score: high risk (A+B)Quantitative score: 9Definitive diagnosis: placenta accreta

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THE PLACENTA

sagittal viewA: Placenta with numerous irregular lacunae and bandsB: Placental-myometrium interface poorly respected in suspicious zoneC: Very dense vascularity in suspicious zone

D: Domed aspectQualitative score: high risk (A+B)Quantitative score: 10Definitive diagnosis: placenta accreta

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THE PLACENTA

sagittal view1) Fusion without Doppler2) Fusion with color Doppler3) Fusion superimposing MRI and color Doppler

A: Placenta with few lacunae and a few bands < 4B: Placental-myometrium interface respected except in suspicious zone (*)C: Regular vascularity except in suspicious zoneD: Usual overall aspect except for doming of suspicious zoneQualitative score: moderate risk (B+C)Quantitative score: 7Definitive diagnosis : Placenta accreta

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THE PLACENTA

Axial view centered on suspicious zone (*)A: Homogenous placenta with no lacunaeB: Placental-myometrium inter-face poorly limited in suspicious zoneC: Vascularity more dense in suspected zoneD: Doming of suspi-cious zoneQualitative score: moderate risk (B+C)Quantitative score: 7Definitive diagnosis: placenta accreta with histology. Planned delivery possible, treatment for hemor-rhage after delivery

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THE PLACENTA

axial view of a placenta percreta left in place day 45 following the cesarean.

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THE PLACENTA

BibliographyRiteau AS, Tassin M, Chambon G, Le Vaillant C, de Laveaucoupet J, Quéré MP, Joubert M, Prevot S, Philippe HJ, Benachi A. Accuracy of ultra-sonography and magnetic resonance imaging in the diagnosis of placenta accreta. PLoS One. 2014 Apr 14;9

Warshak CR, Ramos GA, Eskander R, Benirschke K, Saenz CC, Kelly TF, Moore TR, Resnik R (2010) Effect of predelivery diagnosis in 99 conse-cutive cases of placenta accreta. Obstet Gynecol 115(1):65–69

Yang JI, Lim YK, Kim HS, Chang KH, Lee JP, Ryu HS (2006) Sonographic findings of placental lacunae and the prediction of adherent placenta in women with placenta previa totalis and prior Cesarean section. Ultrasound Obstet Gynecol 28(2):178–182 25.

Twickler DM, Lucas MJ, Balis AB, Santos-Ramos R, Martin L, Malone S, Rogers B (2000) Color flow mapping for myometrial invasion in women with a prior cesarean delivery. J Matern Fetal Med 9(6):330–335

Pasto ME, Kurtz AB, Rifkin MD, Cole-Beuglet C, Wapner RJ, Goldberg BB (1983) Ultrasonographic findings in placenta increta. J Ultrasound Med 2(4):155–159 27.

Baughman WC, Corteville JE, Shah RR (2008) Placenta accreta: spectrum of US and MR imaging findings. Radiographics 28(7):1905–1916

Lerner JP, Deane S, Timor-Tritsch IE (1995) Characterization of placenta accreta using transvaginal sonography and color Doppler imaging. Ultrasound Obstet Gynecol 665(3):198–201

Thorp JM Jr, Councell RB, Sandridge DA, Wiest HH (1992) Antepartum diagnosis of placenta previa percreta by magnetic resonance imaging. Obstet Gynecol 80(3 Pt 2):506–508

Lax A, Prince MR, Mennitt KW, Schwebach JR, Budorick NE (2007) The value of specific MRI features in the evaluation of suspected placental invasion. Magn Reson Imaging 25(1):87–93