Practice exam Flashcards
What is gastrulation?
The formation of the trilaminar disc from the bilaminar disc.
three primary germ cell layers: ectoderm, mesoderm, and endoderm
What is neurulation?
The formation of the neural plate and its closure to form the neural tube
process begins in the fifth week in the thoracic region and extends caudally and cranially, resulting in complete closure by the end of the sixth week (day 42).
Failure of closure of the neural tube results in neural tube defects.
What is the FMF angle a marker for in the first trimester?
aneuploidy
What is the normal FMF angle?
< 85 degrees
List two ways of distinguishing an interstitial ectopic pregnancy from a high
implantation of a normal pregnancy
Interstitial line sign
Double decidual sign
True or False- Cardiac Arrhythmia in first trimester is a benign finding?
True
True or False- Low level echoes in the yolk sac in first trimester is a benign finding?
True
List 2 abnormalities that are seen in Triploidy
Cystic placenta
growth-retarded fetus
degeneration of fetal parts
renal, brain, heart abnormalities
The author of the Twin twin transfusion staging is
Quintero
List 4 second trimester markers that alter risk the patient’s risk of Down Syndrome in
an otherwise, low risk patient.
Nuchal fold >6mm Absent or hypoplastic nose Cardiac defect Short femur and humerus Echogenic bowel Hypoplasia of the fifth digit Omphalocele
Congenital cataracts are associated with
Aneuploidy (trisomy 21)
Two differential diagnoses for a branching LVOT are
Double aortic arch
Transposition of the great arteries (because pulmonary artery is coming out of the left ventricle and branching as it usually does)
Aberrant left common carotid
Aberrant left subclavian
Define the following terms relating them to ultrasound:
(a) Threatened abortion
When there is bleeding in the subchorionic space that is not significant enough to cause embryonic demise.
The cervix is closed.
Define the following terms relating them to ultrasound:
(b) Incomplete abortion
When there is evidence of RPOC
Hyperaemic, echogenic.
Can have severe bleeding that leads to hypovolemic shock and death
When bleeding continues one week after a suspected complete abortion then it is complete
Define the following terms relating them to ultrasound:
(c) Inevitable abortion
Once the cervix is open it becomes inevitable
Bleeding usually increases
Strong contractions may follow
Define the following terms relating them to ultrasound:
(d) Missed abortion
the embryo dies but the gestational sac is retained
uterus is smaller than expected for the gestation
eventually expelled spontaneously, but sometimes not for many weeks.
A suction curettage is therefore often performed
What criteria do you use to establish pregnancy failure in first trimester according to ASUM
policy?
- CRL >7mm with no heartbeat after 30s
- MSD >25mm with no fetal pole
Initial scan showed foetal pole <7mm with no cardiac activity and a repeat scan in 7 or more days also shows no cardiac activity
Initial scan showed an MSD >12mm with no embryo and a repeat scan in 7 or more days does not show interval development of a yolk sac or an embryo with cardiac activity
Initial scan showed an MSD <12mm with no embryo and a repeat scan in 14 or more days shows no visible yolk sac or cardiac activity and the MSD has not doubled
Yolk sac is visible on the initial scan and there is no embryo with a heart beat after 11 days
Absence of cardiac activity which was present on an earlier scan.
Compare and contrast the appearances of the endometrium when there is an early intrauterine pregnancy (pre-appearance of a gestational sac) to the endometrium when there is an ectopic pregnancy.
IUP
The earliest sonographic sign of an IUP is a focal echogenic zone of decidual thickening at the site of implantation at about 3½ to 4 weeks of gestational age. This sign is nonspecific and of limited diagnostic value.
Ectopic
- no specific endometrial appearance or thickness to indicate an ectopic
- Most common appearance during ectopic is normal or increased echogenicity
- Pseudogestational sacs are endometrial fluid collections surrounded by echogenic endometrium form a prominent decidual reaction
Draw and describe the most important biometrical measurement done in weeks 7-13 of
embryonic life.
CRL - crown rump length
The meausrement goes from the crown to the rump
the fetus should be horizontal across the screen and not hyperflexion or extension
Zoomed to fill the screen
Parameters adjusted for crispy edges
3 x measurements at least, from different angles. Take the mean.
Nuchal translucency is used to calculate a risk of Down syndrome in first trimester.
What other ULTRASOUND parameters can be used in first trimester to assist this
calculation.
Describe how these are used and in what circumstances might they be beneficial.
Tricuspid regurg - Abnormalities with the great vessels
Ductus venosus - A-wave anomalies are seen in 80% of fetuses with trisomy 21
Nasal bone - nasal bone abnormalities are significantly more common in trisomy 21 fetuses than in euploid fetuses
In the circumstance where the patient is not having combined screening.
Detection rates of Down syndrome of 80%, 87%, and 94% are reported when using one, two, or three additional ultrasound markers while maintaining the FPR at 3%
beneficial because they increase the detection rate
Draw the correct anatomical plane for the measurement of the nuchal fold noting the
important relationships and anatomical structures.
Cerebellar plane Cavum septum pellucidum Thalami Cerebellar hemispheres and vermis Cisterna magna Falx Anterior horns of the lateral ventricles
Define and list the sonographic appearances of:
(a) Macroglossia
Large tongue
Protrusion of the tongue between the lips
will remain out even during swallowing movements
May be polyhydramnios due to swallowing problems
best visualised on midsagittal plane
Define and list the sonographic appearances of:
(b) Aqueductal stenosis
Overt ventriculomegaly Dilated third ventricle Normal 4th ventricle Post fossa also normal Associated parenchymal thinning
Define and list the sonographic appearances of:
(c) Potters syndrome
A mix of findings as a result of prolonged oligohydramnios due to bilateral renal agenesis Pulmonary hypoplasia Oligohydramnios Wrinkled skin Low set ears extremity deformities retrognathia renal agenesis hypotelorism FGR
the sonographic appearances and significance of gastroschisis
Protrusion of the bowel from the anterior abdominal wall to the right of the umbilical cord insertion
Cauliflower appearance
No covering by membranes
Gastroschisis is not associated with aneuploidy
Associated with teen pregnancy and alcohol and substance abuse
the sonographic appearances and significance of an omphalocele.
Herniation of the bowel and other abdominal structures into the base of the umbilical cord.
Covered by a thin membrane consisting of peritoneum and amnion
cord inserts into the sac itself
If just bowel more likely to be associated with aneuploidy
Smooth walled
potential displaced stomach
Contents may include bowel or liver
What is tetralogy of fallot
VSD
Overriding aorta
Right ventricular hypertrophy (rarely seen in utero
Pulmonary artery (RVOT) stenosis
What views should you use to assess TOF?
4ch - for VSD
RVOT
LVOT - Right displacement of the aorta, VSD, overriding aorta
3VV - aorta may be larger than pulmonary artery due to stenosis/atresia
What views should you use to assess TOF?
4ch - for VSD
RVOT
LVOT - Right displacement of the aorta, VSD, overriding aorta
3VV - aorta may be larger than pulmonary artery due to stenosis/atresia
How do you use LVOT view to assess TOF?
Right displacement of the aorta, VSD, overriding aorta. Identifying the absence of a pulmonary artery branching off the LVOT helps to differentiate from truncus arteriosus.
A patient presents for an 18-20 morphology scan and there is significant maternal adipose
tissue between the transducer and the fetus. List modifications to your ultrasound system
set-up that will improve the quality of your imaging.
*NB Note the change and the impact of the change on the image
Lower frequency transducer
Better resolution at greater depth
Lower frequency harmonics
Improves contrast resolution
dynamic range (increase and decrease) - decrease your dynamic range which will increase your contrast resolution
implementation of compound imaging in the setting is essential
reduces image artifacts and thereby improves tissue-plane definition
Define oligohydramnios
Abnormally low volume of amniotic fluid. Defined as deepest vertical pocket <2cm and at least 1 cm wide or AFI <5.
discuss the significance oligohydramnios of this finding in second trimester
Pulmonary hypoplasia Suggests severe renal malformation IUGR Can indicate premature rupture of membranes Chromosomal disorders Presumed placental dysfunction abnormal swallowing
Describe in detail, your examination of the fetus for spina bifida at the head and sonographic appearances that you may see.
Head
Anencephaly
Exancephaly
Chiari II malformation - Classic sonographic sign is the deformation of the cerebellar shape ‘banana sign’ and the non-visualisation of the cisterna magna
Most common manifestation is the obliteration of the cisterna magna
Concave deformity of the foetal frontal bones cause the lemon sign
Nonvisualisation of the intracranial translucency (4th ventricle)
Describe in detail, your examination of the fetus for spina bifida at the lumbar spine and sonographic appearances that you may see.
Laminae fail to converge towards the midline
Increased interpedicular distance
Pedicles may diverge away from the midline instead of being parallel
Absent overlying skin or subcutaneous tissue
Describe your Spectral Doppler assessment of the Umbilical Artery in third trimester.
Include in this discussion:
(a) Normal spectral waveforms
To produce an accurate measurement UA-PI must be
measured from a free-floating portion of cord
with an angle of insonation as close to 0 degrees as possible
never exceeding 30 degrees
observations based on at least 3 consecutive waveforms
Flow in the umbilical artery is normally low resistance
with an S/D ratio of less than 3.5 up to 28 weeks’ gestation
less than 3.0 thereafter
Describe your Spectral Doppler assessment of the Umbilical Artery in third trimester.
Include in this discussion:
(b) Abnormal spectral waveforms
As placental insufficiency worsens there is higher placental resistance leading to an increased PI and absent or reversed end-diastolic flow
Describe your Spectral Doppler assessment of the Umbilical Artery in third trimester.
Include in this discussion:
(c) The reasons that the waveform changes occur.
Bad measurement
Breathing
Fetal movement
Abnormal UA correlates with placental dysfunction and foetal compromise
Often provides early warning of foetal distress
Describe the method of measuring fetal weight in the third trimester
AC is the most important measurement
HC
BPD
FL
Briefly describe the key components of a biophysical profile.
Breathing - 30 seconds continuous
Tone - 1 episode of extension and flexion
Movement - 3 discrete body and limb movements
AFI - single pocket 1cm across and 2 cm deep at least
Briefly discuss the recommendations which
ensure ultrasound systems are safe.
Heating
TI ≥ 1 must be indicated on the scanner display screen
Only perform a scan when medically indicated
The examination should be undertaken in the minimum time with the lowest possible power consistent with a diagnostically meaningful image
The sonographer should not rest the transducer on the patient when on, but not actually scanning
Be particularly careful about dose when using spectral Doppler (power high), and when scanning bone (thermal effects)
Briefly discuss the thermal biological effects of ultrasound
central nervous system (CNS) is most at risk
neural tube (anencephaly, microencephaly) and the eyes (microphthalmia, cataract)
Associated with CNS defects are functional and behavioral problems
Other organ defects secondary to hyperthermia include:
defects of craniofacial development (e.g., clefts)
anomalies of the axial and appendicular skeleton
the body wall
teeth
heart
Gestational age is critical when considering heat dispersion
In early human pregnancy, less than 6 weeks, the minimal fetal perfusion may reduce heat dispersion
Chorionic Villi Sampling
10 -12.6 weeks
only diagnostic
higher miscarriage risk ~1%
main indication is karyotyping
Amniocentesis
15 - 20 weeks
can be therapeutic as well as diagnostic
Lower miscarriage risk ~0.5%
main indication is karyotyping
differences between the fetal and post
natal circulatory system
Fetal shunts
Ductus venosus
Foramen ovale
Ductus arteriosis
Oxygenated blood -> placenta -> umbilical vein -> Ductus venosus -> IVC -> right atrium -> left atrium -> Aorta -> umbilical arteries
List three ultrasound system B-mode changes that may help you to differentiate between
dropout and an interventricular septal defect.
• using multiple scanning planes to view the regions, preferably with the scan plane perpendicular to the septum; and - increase gain - Use lower frequency transducer - decrease dynamic range ?using colour flow imaging. ?power imaging
discuss the first trimester determination of chorionicity and amnionicity.
From 8 weeks, it is possible to visualise the amnion, allowing for the determination of amnionicity
Prior to 8 weeks, the number of yolk sacs can also be used to determine amnionicity
Dichorionic:
Easily seen at 6 weeks with two separate chorions, within each sac there will be a yolk sac
Twin peak sign/lambda sign
Membrane thickness >2mm
Monochorionic:
Single chorion
No amniotic membrane seen until approximately 8 weeks
Two yolk sacs means its probably diamniotic
Single yolk sac with 2 foetuses = probably monoamniotic
Repeat scan at 9 weeks
