Ultrasonography in Obstetrics

Dr. Szabó Gábor

Budapest, 2019.09.27.

Ultrasound

• Ultrasound refers to sound with frequencies above the audiblefrequency range of humans and includes frequencies from about 16kHz. Ultrasound from a frequency of about 1 GHz is also referred toas hypersonic. At frequencies below the audible frequency range forhumans one speaks of infrasound.

• In gases and liquids, ultrasound propagates only as a longitudinalwave. In solids it also comes due to the shear stresses occurring forthe propagation of transverse waves. The transition from airbornesound to solids or liquids takes place only when the sound waves areradiated in the immediate vicinity or a coupling medium withadapted acoustic properties and a certain thickness in between.

Basic physical terms

• Over 20000 Hz Frequency - For Medical Use Between 2-20 Megahertz (106)

• Piezoelectric phenomenon, and electronic processing of the data from the reflected sound wave

• In liquid, the sound wave spreads excellent. Most tissues of the organism are all highly water-containing (blood vessels, tubular and parenchymatous viscera

• The differences in the reflected frequencies of the different tissues give the opportunity to produce images.

• In real-time mode (25 frames / per second)

• Depending on the material of an obstacle, ultrasound is reflected on it, absorbed in it or passes through it (transmission). As with other waves, refraction, diffraction, and interference also occur.

• Air has a strong attenuation with increasing frequency for ultrasound. In liquids, on the other hand, ultrasound spreads to a certain intensity with little attenuation.

• From a threshold, however, there is the formation of vapor bubbles (cavitation), which can cause extremely high pressures and temperatures when they collapse. At frequencies between 2 and 20 MHz, to prevent cavitation in pure, degassed water, the sound pressure must not exceed 15 MPa. This effect is exploited for ultrasonic cleaning and is also an interesting research subject (sonoluminescence).

Ultrasound in the nature

The discovery of the piesoelectric effect

• In 1880 brothers Jacques and Pierre Curie discovered the piezoelectric effect

• Piezo effect describes the interaction of mechanical pressure and electrical voltage of certain crystallites

• direct piezoelectric effect: mechanical deformation of certain crystals generates electrical charge on the crystal surface

• Inverse piezo effect: Crystals deform when an electrical voltage is applied

Application in medicine

Today one of the most popular imaging techniques in medicine

Low-risk, painless and cost-effective procedure

It does not emit ionizing radiation

mechanical index - cavitation effect

thermal index - warming effect

During rutine use it is a safe method.

In early pregnancy Doppler method is only limited applicable

Image modes• "A" mode (Amplitude)

• The one-dimensional representation of the reflected ultrasonic pulse in a diagram as a curve peak (peak). The x-axis of the graph indicates the depth of penetration and the y-axis the amplitude (intensity) of the echo. The stronger the reflection at a tissue boundary, the higher the signal amplitude.

• "B" mode (brightness)

• In B mode, a section of the body is displayed as a sectio dimensional image. Instead of the peak of the A mode, the echo is converted into pixels of different shades of gray. The higher the signal amplitude, the brighter the pixel (brightness modulation). Each reflected ultrasonic wave (echo) is spatially assigned and displayed as a dot in the image. The position of the pixels along a line again corresponds to the reflected layers. Many lines next to each other form a two-dimensional image. A moving picture is created by temporal juxtaposition of single pictures.

• (T) M (time) motion mode,

• motion sequences, temporal changes of a moving object is displayed. On the vertical, a single line of the B mode image is recorded.

• Doppler mode

• 3D, 4D, 5D ...

Image modes

Time

Doppler effect

• In the event of an oncoming wave, the wave will be frequent,and will elongate as it moves away

• Therefore, as the source of the waves approaches us, the wavelengths are shorter than those emitted by the stationary source, and the waves of the receding source are longer.

• That is, why the sound is perceived as higher or deeper.

Christian Doppler

Hungarian Society for Ultrasound in Obstetrics and Gynecology since 1992

License training and examination after specialization

FMF

Fetal Medicine Foundation – London Kypros Nicolaides

ISUOG –

International society of Ultrasound in Obstetrics and

Gynecology

Protocols - Guidelines

White Journal - UOG

Which conditions do you need for an excellent

scanning?

1. A good device

2. Theoretical knowledge

- Anatomy, Embryology, Physiology, Obstetrics and Gynecology,

Histology

3. Time and practical experience

Geburtshilfliche Routineuntersuchungen

• 0. Ultrasound examination (in early pregnancy)

• 1st Ultrasound examination (11-13th week of pregnancy)

(first trimester screening)

• 2nd Ultrasound examination (18-21st week of pregnancy)

(second trimester screening)

• 3rd Ultrasound examination (28-32th week of pregnancy)

• 4th Ultrasound examination (36-38th week of pregnancy)

0. Ultrasound ScreeningQuestions to be answered

• Is the pregnancy detectable?

• Single or multiple pregnancy?

• Is the embryo alive?

• Where is the amniotic sac? In the uterine cavity? Ectopic?

• For which pregnancy week does the embryo correspond? Is there a difference between ultrasound and Nagele rule:

• Are there any signs of an imminent spontaneous abortion or premature placental abruption?

• Are the ovaries regular? Is there a luteal body?

• Is there any pathological structure in the pelvis?

EARLY PREGNANCY ULTRASOUND SIGNS

Intrauterin pregnancy

Embryonal sac 4-5. GW

Yolk sac 5. GW

Cardiac activity 5-6. GW

Ectopic pregnancy

Pseudogestational ring 20%

Free fluid in the abdominal cavity 56%

Irregular Adnex lesion 60%

Ectopic embryonalsac, Embryo or cardiacactivity

20%

If the diameter of the gestational sac is more than 25 mm and there is no embryo or the

crown-rump length of the embryo is more than 7 mm but there are no cardiac activity then

there is an increased risk of spontaneous abortion.

If the diameter of the gestational sac is between 16 to 24 mm, or the crown-rump length of

the embryo is below 7 mm and it does not show any cardiac activity, then a check-up must

be made after 11-13 days.

0. and 1. UH Screening –Estimation the date of delivery

• If the estimated date of delivery due Naegele1 rule and the measured biometric parameters show more than a week difference → A new date of delivery should be estimated due ultrasound at the 11-13 estational week.

• Deviations of biometric parameters from the average

• - 6-8 weeks (CRL) 3-5 days

• - 11-13 weeks (CRL, BPD) 6-7 days

• - 18- 20 weeks (BPD, ..) 1-2 weeks

• - In the third trimester biometry 2-3 weeks

• In the third trimester due to the biometric data you can not change the estimated date of delivery!

First trimester ultrasound screening

• Between the 11 weeks -13 week 6 days

• The Most Effective Morbus Down Screening Method.

• About 70-80% sensitivity !!

The FMF criteria of screening Down syndrome in the first trimester

• (NT nuchal translucency) measurement

• - 45-84 mm crown-rump-length (CRL) – 11+0 - 13 weeks 6 days gestation

• - mid-sagittal position,

• - neutral position

• - optimal magnification (calliper on the head and upper thorax 0.1 mm)

• - low gain

• - Embryo removed from uterine wall and amnion

• - Measurement of nuchal translucency (on-on)

• - Under 3 mm normal, but it is also related to CRL

• Accurate measurement !!!

Ultrasound sign of the cromosome abnormalities in the first trimester

• - Thickened nuchal translucency - Cystic hygroma) - Oedema on the whole body, hydrops)

• - Lack of the nasal bone

• - Enlarged fronto-maxillo-facialis - or FMF angle)

• - At the end of the umbilical vein (ductus venosus) (in diastole stop, or reverse flow).

• - Reverse flow detectable during systole in the heart between the right atrium and right ventricle (tricuspid regurgitation)

Examination of the nasal bone

• John Langdon Haydon Down

(1828 November 18. – 1896 October 7.)

Illustration of the nasal bone with ultrasonography

• CRL: above 42 mm, the nasal bone is visible

• Mediansagittal view.

Transducer should be parallel with

the fetal nose, and 45o with the

longitudinal axis

Below 45o and above 135o the nasal

bone can "disappear".

The physiological ultrasound image of the nasal bone

It is more echogenic than the skin.

Three separate lines should be visible:

- Upper: The skin of the nose

- Lower echogenic line: the nasal bone

- Continuation of the first line: The tip of

the nose

Absence of the nasal bone

• The ossification of the nasal bone is delayed.The pathophysiological process is notcompletely known.

• In trisomy 21 and 18 pathognostic. In 60-70%of fetuses with Down syndrom the nasal boneis missing (in healthy fetus only in 2%)

Nasal Bone length

• In the second trimester on Down syndrome specific anomaly is the hypoplasia of the nasal bone.

CRL: 45 mm - NBL: 2,48 mm, CRL: 84 mm - NBL: 3,12 mm

Paulo Sérgio Cossi et al. Measurement of fetal nasal bone length in the period between 11 and 15

gestational weeks in a Brazilian population: a preliminary study. Radiol Bras vol.41 no.3 São

Paulo May/June 2008 CRL: 45 mm - NBL: 1,69 mm, CRL: 84 mm - NBL: 2,34 mm

Orlandi, F., et al. (2003), Measurement of nasal bone length at

11–14 weeks of pregnancy and its potential role in Down

syndrome risk assessment. Ultrasound Obstet Gynecol,

22: 36–39.

Fronto-maxillo-facial Angle

• The angles between frontal bone andpalate

CRL: 45 mm - FMF: 83,5o, CRL: 84 mm - FMF: 76,4o

Frontomaxillary facial angle in fetuses with spina bifida at 11–13 weeks’ gestationR. LACHMANN, et al. Ultrasound Obstet Gynecol 2010;36: 268 – 271

Examination of the tricuspid valve

• Risk assessment of trisomy 21 and heart development failure in the first trimester

• Regurgitation in 0.9% of euploid fetuses% and 55% in fetuses with 21 trisomy.

(Kagan KO, Valencia C, Livanos P, Wright D, Nicolaides KH, Ultrasound ObstetGynecol, 2009 Jan 33(1) 18-22)

• Apical four chamber view

• Pulse wawe Doppler:2.0-3.0 mm gate

• The direction of the ultrasonic wave and the flow through the flap are parallel

Tricuspidalis regurgitatio - Doppler Bild

Tricuspid regurgitation

More than half of the systole

shows a regurgitation. The

speed of the return flow is

more than 60 cm / sec (The

speed of aorta and pulmonary

artery is 50 cm / sec max.)

Fetal circulation

3 shunts

1.Ductus venosus

-Liver bypass

2. Foramen ovale

-Lung bypass

3. Ductus arteriosus

-Lung bypass

Examination of the ductus venosus pulse wawe

• Fetal umbilical vein brings fresh blood directly into the coronaries and into cerebral circulation

• Ventricular Systole (S), Ventricular Diastole (D), and Atrial Contraction (A) Wawe

• Positive flow through the whole cycle

Normale und pathologische „A” Welle

é

Normal and pathologic Flow in the Ductus venosus

Megacystis

• 7-15 mm: 23%, over 15 mm 11% cromomosomal abnormalities

• About 15 mm mostly an obstructive

uropathy (keyhole sign)

• Physiologic: less than 7 mm on the 13th week of pregnancy

• Upper border of the bladder superior to the navel

Exomphalos

• After the 11 weeks and 5 days it is pathognostic. Before it can mean a physiological gut herniation.

Umbilica cyst

Single umbilical artery

Fetal heart rate

• At the 10 gestational week physiological: 100 / minute

• At the 14th gestational week: 155 / minute

• Trisomy 13 and Turner syndrome – tachycardia

• Trisomy 18 and Triploidia – Bradycardia

• Trisomy 21 mild increase in frequency

Hyperechogenic bowels

Second trimester screeining at the 18-22. gestational weeks

- „traditional" genetic ultrasound

- placenta, amniotic fluid, fetal position

- biometrics (BPD, HC, AC, THQ, FL, HL,… ..)

- fetal anatomy and detailed examination of organs

(thorough examination of the skull, face, limbs, chest, heart,

diaphragm, abdomen, abdominal organs, stomach, kidneys, spine)

0

Examination of the fetal heart at the 18-22weeks with ultrasonography• Heart development failures are the

most common congenital malformations (4-13 / 1000 live births)Compulsory four-chamber viewexamination can detect only a fraction of the vitriols intrauterine (senitivities 7-56%) / Concalves et al. Clin Obstet Gynecol 2012; 55: 266-80 /Conotruncal anomalies (Fallot, large vessel transposition, ..) can only be detected by examining the outflow tracts!From 2013, according to the ISUOG protocol, examining outflow tracts is part of the 18-20 week screening!

Screening of Down syndrom in the second trimester

The efficiency of Down's screening with ultrasound in the second trimester is only ~ 40-50% !!

Search for minor signs →

- Ultrasonography signs that may occur in normal healthy fetuses but the are warning.

Ultrasonographic markers of chromosome anomalies during the second trimester screeningMinor signs (soft markers)

Plexus chorioid cyst (CPC)

single umbilical artery

echogenic intracardial focus

short tubular bones

Nasal bone hypoplasia (NB, PT)

ventriculomegaly

neck odema (NF) nuchal fold

facial cleft

pyelectasia

clubfoot

finger, hand disorders

growth retardation

oligohydramnios

Major signs

cardiac development failures

(ventricular septum defects, Ebstein, Fallot ..)

exomphalos

duodenal atresia

esophagal atresia

diaphragmatic hernia

The examination of the nasal bone and prenasalterritory (PT/NB ratio)

• This second trimester marker was publishedin 2005-ban. One of the easisest to examine.

Maymon et al., Second trimester ultrasound prenasalthickness combined with nasal bone length: a new method of Down syndrom screening, Prenat Diagn 2005, 25, 906-911

• PT: Shortest distance between the lowerborder of the frontal bone and the skin surface

• NB: length of the nasal bone

• PT / NB ratio in healthy fetuses is 0.5-0.7

• In fetuses with Down syndrome, the rate is significantly increased

Obstetric ultrasonographyThird trimester ultrasound screening- between the

30-32. gestational week

- position of the fetus

- the amount of amniotic fluid

- location and maturity of the placenta

- biometry

- examination of organs (heart, diaphragm, kidneys)

- flowmetry

→ uteroplacental circulation - a. uterina

→ fetal circulation- a. umbilicalis, descending aorta,

Middle cerebral artery

↓

placental disorder, fetal retardation,

early detection of preeclampsia (notch)

Amniotic fluid volume

• Semi-quantitative methods

• Largest amniotic fluid pocket (under 2 cm)

• AFI (four quadrants, amniotic fluid index) below 5 cm

• Chronic hypoxia, screening of premature rupture of the membranes

Obstetric ultrasonography

Third trimester ultrasound screening- between the

30-32. gestational week

• - Detection of certain disordersdiaphragmatic hernia, duodenum atresia,microcephalia, dysgenesis of thecorpus callosum,dilated pyelons

• - early diastolic notching

a sign of uteroplacental circulation disorder(in preeclampsia as early as weeks 20-24)Cause: Inappropriate trophoblast invasion →muscular layer of spiral arteriolespersists → placental circulation disorder

Before

pregnancy1. trimester

2. trimester 3. trimester

Maternal site – Uterine arteries

Examined by

abdominal transducer

At the level of virtual

intersection between

uterine arteries and

external iliac vessels.

Notch 0-1Notch 1

Notch 2Notch 3

Notch 4

• Contralateral, single-sided diastolic depression does not worsen outcome

• Bilateral notch control?

Alteration of umbilical artery flow during pregnancy

Pulsatility index at the umbilical artery throug

the pregnancy

Terhességi kor

Umbilical artery Doppler

The lowest end-diastolic velocity is near the abdominal origin physiologically

Reverse flow at the umbilical arteries

Middle cerebral arteryDoppler examination

Higher resistance values compared to

umbilical artery.

The most studied vessel in brain circulation

examination. These arteries are the branches

of the carotid arteries. It provides two thirds

of the blood supply to the brain.

Obstetric ultrasonography

Late third trimester ultrasound screening- between the

36-38. gestational week

- the position of the fetus

- amount of amniotic fluid

- position and maturity of the placenta

- Biometric parameters

- vital signs, intrauterine condition, flowmetry, biophysical profile

- estimating the mode of the delivery

Three dimensional ultrasonography – 3D

• It is a rapidly developing technique since the 90's

• Coronal plane adjacent to the two basal planes (frontal, sagittal) for the examination of the selected volume

• The planes can be rotated and turned → almost any sectional view

• The basic unit of volume representation is voxel

• steps:

• - mapped object (volume box, ROI)

• - examination and adjustment of the selected volume in three sections

• - 3D reconstruction (volume rendering)

• 3D reconstruction, transparent mode, surface rendering, maximum mode inverse mode etc…

Thank You for your Attention!