Imaging the Nervous System

Question 1

What is the CNS imaging modality of choice in neonates and infants?

Answer 1

Cranial ultrasound

Question 2

Why is cranial ultrasound the imaging modality of choice in neonates and infants?

Answer 2

Due to the ease of scanning via the open anterior fontanelle

Question 3

What are the advantages of cranial ultrasound?

Answer 3

Quick and non-invasive

Question 4

What are the disadvantages of cranial ultrasound?

Answer 4

Highly operator dependant

Question 5

What do repeat cranial ultrasounds over time allow for?

Answer 5

Evolution and progression of lessons to be monitored

Question 6

What is cranial ultrasound particularly used for?

Answer 6

• Intraventricular haemorrhage
• Ischaemic cysts of periventricular leukomalacia (PVL)
• Ventricular dilatation
• Range of cerebral malformations and other lesions, e.g. agenesis of the corpus callosum

Question 7

What is MRI much better at than cranial ultrasound?

Answer 7

• Detecting ischaemic lesions, e.g. hypoxic-ischaemic encephalopathy or PVL
• Detailed anatomy of cerebral malformations

Question 8

What are the advantages of cranial CT?

Answer 8

• Widely available

- Rapid

Question 9

What is cranial CT used for?

Answer 9

• Head trauma
• If clinical condition unstable
• Intracranial calcification
• Haemorrhage

Question 10

How can cranial CT images be enhanced?

Answer 10

With the use of contrast

Question 11

Why has cranial CT been largely replaced by MRI?

Answer 11

• Does not require radiation

- Usually more informative

Question 12

What is MRI imaging the technique of choice?

Answer 12

In most paediatric neurological disorders

Question 13

What is the purpose of different sequences in MRI?

Answer 13

Can be used to interrogate the signal to answer particular clinical questions

Question 14

What are the different sequences in MRI?

Answer 14

• T1
• T2
• FLAIR (fluid attenuated inversion recovery)

Question 15

Describe the appearance of CSF, grey matter, and white matter on T1 MRI sequence?

Answer 15

• CSF appears black
• Grey matter is grey
• White matter is white or paler grey

Question 16

What is T2 sequence used for?

Answer 16

Assessing tissue fluid contents, such as oedema

Question 17

How does CSF appear on T2 MRI sequence?

Answer 17

White

Question 18

What is FLAIR sequence used for?

Answer 18

Lesions close to the ventricles

Question 19

What is the purpose of FLAIR sequence?

Answer 19

Signal from CSF is reduced to allow clearer tissue imaging

Question 20

How does a solid mass appear on;

a. T1
b. T2
c. FLAIR?

Answer 20

a. T1 - dark
b. T2 - bright
c. FLAIR - bright

Question 21

How does a fluid-filled cyst appear on;

a. T1
b. T2
c. FLAIR?

Answer 21

a. T1 - dark
b. T2 - bright
c. FLAIR - dark

Question 22

How does subacute blood appear on;

a. T1
b. T2
c. FLAIR?

Answer 22

a. T1 - bright
b. T2 - bright
c. FLAIR - bright

Question 23

How does a acute and chronic blood appear on;

a. T1
b. T2
c. FLAIR?

Answer 23

a. T1 - grey
b. T2 - dark
c. FLAIR - dark

Question 24

How does fat appear on;

a. T1
b. T2
c. FLAIR?

Answer 24

a. T1 - bright
b. T2 - dark
c. FLAIR - bright

Question 25

What has increased availability of MRI scanning in children allowed for in a wider sense?

Answer 25

Expand knowledge about pathological processes occurring in children with encephalopathy

Question 26

What does functional MRI allow for?

Answer 26

Visualisation of regional oxygen consumption and blood flow

Question 27

What is functional MRI used to examine?

Answer 27

Brain activity

Question 28

What does functional MRI create?

Answer 28

A map showing which parts of the brain are involved in a particular task, such as movement or speech

Question 29

Where is functional MRI being increasingly used?

Answer 29

In pre-surgical assessment of children being considered for epilepsy surgery

Question 30

What does functional MRI allow in the pre-surgical assessment of children being considered for epilepsy surgery?

Answer 30

More accurate prediction of post-op functional outcome

Question 31

Give an example of a disorder that functional MRI has enhanced understanding of?

Answer 31

Autism

Question 32

What is MRA?

Answer 32

Magnetic resonance angiography

Question 33

What does MRA permit?

Answer 33

Non-invasive assessment of the intracranial vascular system

Question 34

Where is MRA of particular use?

Answer 34

Conditions such as intracranial arteriovenous malformations, e.g. Sturge-Weber syndrome, and blockages/stenosis

Question 35

What is MRS?

Answer 35

Magnetic resonance spectroscopy

Question 36

What does MRS rely on?

Answer 36

The individual resonance properties of certain molecules within brain tissue

Question 37

Give three examples of molecules that have known resonance properties?

Answer 37

- Lactate - Choline - Creatinine

Question 38

What can MRS detect?

Answer 38

High levels of metabolites or other target molecules in conditions

Question 39

Give 5 examples of conditions that might have high levels of metabolites/other target molecules that might be picked up by MRS?

Answer 39

- HIE - Brain injury - Epilepsy - Metabolic disorders - MS

Question 40

What does raised lactate on MRS signal?

Answer 40

A metabolic disorder

Question 41

What is a promising area of research with MRS?

Answer 41

Into tumours, as choline signals are often elevated in tumour tissue

Question 42

Is MRS widely available?

Answer 42

No, restricted to larger research centres

Question 43

How does PET imaging work?

Answer 43

A labelled radioactive tracker is injected into the body, which gives off gamma rays that are detected by a scanner

Question 44

What does the information gained from PET imaging depend on?

Answer 44

What molecule the tracker was attached to

Question 45

Give an example of a molecule a tracker might be attached to on PET, and what these images would reflect?

Answer 45

Flurodeoxyglucose | Images will reflect regional glucose uptake, and therefore the metabolic activity of the tissue

Question 46

What is the main indication of PET scanning in paediatric neurology?

Answer 46

To identify precise areas of seizure onset in focal epilepsy, therefore identifying possible targets for epilepsy surgery