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C1 Modules > Fetal Imaging > Flashcards

Fetal Imaging Flashcards

1
Q

What is ultrasound used for?

A

Primary screening modality for obstetric and foetal imaging

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2
Q

What are the advantages of fetal imaging?

A
  1. Low cost
  2. Easy access
  3. Quicker
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3
Q

What are the advantages of fetal imaging?

A
  1. Reduced FOV
  2. Lower spatial resolution
  3. Poor soft tissue contrast
  4. Operator dependent
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4
Q

What is Foetal MRI?

A

Complementary tool

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5
Q

What are the safety features of foetal imaging?

A
  1. Operate within radiological safety guidelines
  2. Avoid first trimester
  3. Screen for metal
  4. Issues with claustrophobia and high BMI
  5. Minimise heating effects: operate sequences with low SAR (specific absorption rates)
  6. Minimise noise e.g. add soft tone
  7. No reported detrimental effects to fetus
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6
Q

What are the features of foetal MR imaging?

A
  1. Relatively new technique (1980’s)
  2. Motion is a major problem
  3. Initial studies paralysed fetus
  4. Maternal sedation
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7
Q

Why is foetal MR imaging relatively new technique?

A
  1. Complementary to ultraound
  2. Improve detection rate of abnormalities
  3. Improve characterisation of known abnormalities
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8
Q

What are the optimal brain sequences essential for optimal clinical scan?

A
  1. 3 planes T2 (fast spin echo)
  2. Axial T1-weighted
  3. Axial Diffusion weighted (ischaemia)
  4. T2 GRE (haemorrhage)
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9
Q

What are the body sequences essential for optimal clinical scan?

A
  1. T2 (fast spin echo)
  2. T1 (meconium in the rectum)
  3. T2 GRE (good for spine)
  4. T2 TRUFFI (good for spine and placenta)
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10
Q

What are essentials for optimal clinical scan?

A
  1. Always have all clinical and ultrasound data available
  2. Experienced interpreter
  3. Understanding of relevant pregnancy termination laws
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11
Q

What are the features of foetal motion?

A
  1. Single slice fast acquisition - no artefacts unless movement, very quick
  2. Fetus move in and out of plane during acquisition
  3. Incomplete coverage of brain and rotated views may make interpretation difficult
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12
Q

What does snap shot image with volume reconstruction (SVR) provide?

A
  1. High signal to noise
  2. High resolution
  3. 3D volumetric dataset of brain in presence of foetal motion
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13
Q

What does reconstruction allow for?

A

Non-rotated views with full brain coverage

optimal for clinical interpretation

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14
Q

What are the CNS imaging indications?

A
  1. Ventriculomegaly
  2. Agenesis of corpus callosum
  3. Cerebellar anomalies
  4. Congenital infection
  5. Neural tube defect
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15
Q

What is the consequence of CNS imaging indications?

A
  1. Complications of twin pregnancies

2. Acute maternal hypoxic event or illness

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16
Q

When is ventriculomegaly observed?

A
  1. 1% pregnancies atrial diameter > 10mm on ultrasound

2. More frequent in males

17
Q

What are the current practice for ventriculomegaly?

A
  1. Detailed fetal ultrasound
  2. Maternal TORCH screen
  3. Fetal MRI
  4. Consider Amniocentesis
18
Q

MRI in ventriculomegaly

A
  1. Most common indication for MR referral
  2. Detection any obvious cause for ventriculomegaly
    - haemorrhage/obstruction
  3. Identification additional anomalies
  4. Inform further investigations
  5. Helps on outcome predicition and counselling
19
Q

When does isolated ventriculomegaly cause neurodevelopmental impairment?

A

Atrial > 15mm up to 75%

20
Q

What are the causes of ventriculomegaly?

A
  1. Ventricular dilation with evidence of germinal matrix haemorrhage
  2. Haemorrhage involves basal ganglia
  3. Posterior limb of internal capsule
21
Q

Agenesis of corpus callosum

A

Incidence 0.5 -70 per 10,000

Variable outcome (approx. 30% moderate /severe)

Exclude other abnormalities as outcome worse (increased detection with MRI 22.5%)

22
Q

Agenesis of corpus callosum

A

Chromosomal abnormalities in approx. 17% ( More common when other anomalies)
May be referred from US with ventriculomegaly
Occasionally as a parenchymal cyst

Gender of fetus important to exclude possible Aicardi syndrome (females)

23
Q

What are the cortical anomalies?

A
  1. MRI able to assess cortical maturation
  2. May have early abnormal folding
  3. Delayed or absent folding
  4. Markedly abnormal appearance to cortex posteriorly
  5. Very low signal thickened and abnormally shaped
  6. Probably early polymicogyria
24
Q

What are the cerebellar anomalies?

A 
Large cisterna magna
Cerebellar hypoplasia
Vermis +/- hemispheres
Rhomboencephalosynapsis
Cerebellar haemorrhage
25
Q

What are the postnatal examination?

A 
Anorectal anomaly
Imperforate anus
Micropenis
Choanal atresia
Normal cardiac echo
Normal renal US
26
Q

What are the other postnatal examination?

A 
Coloboma of the eye, 
Heart defects, 
Atresia of the choanae, 
Retardation of growth and/or development, 
Genital and/or urinary abnormalities, 
Ear abnormalities and deafness
27
Q

What are the neural tube defects?

A

Myelomeningocele (most common)
Compatible with life but significant morbidity
Prenatal intervention (few centres)
Delivery and neonatal surgical repair
80% ventriculo-peritoneal shunt placement
Complications, lifelong supportive care
Most present with Arnold-Chiari II malformation

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