Second and Third Trimester- Basic Scan Flashcards
The second trimester is what weeks?
13-27 (3-6 months)
Between what weeks can performing an ultrasound allow you to image all organs and predict due date?
16-26 weeks GA
The spine can be identified sonographically by which week?
16-18 weeks
The spine is completely ossified by?
Week 18
The 3 ossification centers can be seen by?
16 wks GA
What are the 3 ossification centers?
2 posterior (laminae) and 1 and anterior (centrum)
The 3 ossification centers are best seen in which plane?
Transverse
The central portion of the spine appears how sonographically?
hypoechoic
The lumbosacral spine is not completely ossified until?
> 18 wks GA
Where can the lateral ventricles be seen?
on either side of the midline falx
The midline falx is also called?
interhemispheric fissure
The lateral ventricles should not exceed?
10 mm
How do you measure the lateral ventricles?
inner to inner through the atrium
True or False: Both the normal anterior and posterior horns of the lateral ventricles are seen sonographically
False; only posterior horns
Where is hydrocephalus first seen?
lateral ventricles (dilated lateral ventricles or ventriculomegaly)
Where is the choroid plexus located?
in the lateral ventricles
How does the choroid plexus appear sonographically?
echogenic
What is the function of the choroid plexus?
produce CSF
By when is the brain anatomy visualized?
12-14 wks GA
Where can the thalami be visualized?
on either side of the midline
What serves as the landmark for the BPD and HC?
thalami, CSP, midline falx
What is the thin echogenic line seen between the thalami?
third ventricle
Where can the cisterna magna be visualized?
in the posterior fossa posterior to cerebellum
The cisterna magna should never exceed?
10 mm
Where is the cerebellum located?
in the posterior fossa
How does the cerebellum appear sonographically?
two hypoechoic lobes with an echogenic vermis seen between
An absent vermis can cause?
splaying of cerebellum
What is the cavum septum pellucidum (CSP)?
slit like space that is midline separating the anterior horns of lateral ventricles
How does the CSP appear sonographically?
anechoic rectangle in anterior part of the head
Circulation of CSF
- CSF produced by choroid plexus
- Flows through Foramen of Monro to 3rd ventricle (between thalamus)
- Aqueduct of Sylvius connects 3rd and 4th ventricle
- CSF flows through subarachnoid space through the Foramen of Luschka and Foramen of Magendie
- CSF is absorbed into dural venous sinuses via arachnoid villi
The nuchal thickness (nuchal fold) should not exceed?
< 5-6 mm
How does CSF appear sonographically?
anechoic
By when is the 4 chamber heart identified sonographically?
16-18 wks
The apex of the heart should point where?
left side of fetus
Which portion of the heart is closest to the chest wall?
right ventricle
Which portion of the heart is closest to the spine?
Left atrium
The fetal heart should occupy ______ of the chest.
1/3
Where is the tricuspid valve located?
between the right atrium and right ventricle
Where is the mitral/bicuspid valve located?
between left atrium and left ventricle
The foramen ovale shunts blood from?
the right atrium to the left atrium
The foramen ovale turns into what when it closes?
fossa ovalis
Which portion contains more oxygenated blood?
left atrium
What is the normal fetal heart rate?
120-160 bpm
A fetal heart rate of < 100 bpm indicates?
bradycardia