Neuroradiology

Question 1

What are the common indications to perform a CT?

Answer 1

• Stroke
• Head trauma
• Headache
• Cancer
• Post-surgical (hydrocephalus, haemorrhage)

Question 2

When may you not perform a CT scan?

Answer 2

• Minor head trauma exclusion criteria

- Seizure

Question 3

When would a CT not be carried out for a head trauma?

Answer 3

• GCS 15
• No suspected open or depressed skull fracture
• No hemotympanum
• No ‘panda’ eyes
• No CSF leakage from ears or nose
• No post -traumatic seizure
• No focal neurological deficit
• <2 episodes of vomiting
• No amnesia
• Age<65 years
• No coagulopathy
• Not struck by a motor vehicle,
• Not ejected from a motor vehicle
• Fall<1m

Question 4

What are the indications for an MRI scan?

Answer 4

• Epilepsy
• Demyelination
• Paediatric neurology
• Headache
• Spine degeneration
• Cancer
• Stroke

Question 5

What are the contraindications to MRI scan?

Answer 5

• Implanted electronis such as pacemakers and cochlear implants
• Movable metallic implants such as aneurysm clips, heart valves or intrabdominal clips

Question 6

What is angiography used in the diagnosis and treatment of?

Answer 6

• Aneurysm
• Arteriovenous malformations
• Carotidocavernous fistula
• Unstoppable epitaxis

Question 7

Perfusion

Answer 7

The volume of blood passing through a defined volume of tissue per unit time

Question 8

What techniques can be used for perfusion?

Answer 8

CT or MRI

Question 9

What is the units of perfusion?

Answer 9

ml blood/100g tissue/ min

Question 10

Give examples of disorders of abnormal perfusion.

Answer 10

• Stroke decreases perfusion

- Tumour with increased perfusion suggest angiogenesis and a more aggressive tumour

Question 11

What is PET used to do?

Answer 11

Map out glucose usage

Question 12

When can increased metabolism be seen?

Answer 12

• Tumour
• Inflammation
• Infection

Question 13

When is PET useful?

Answer 13

Useful after brain tumour resection for differentiating granulation tissue (low energy use) from leftover tumour (high energy use)

Question 14

What are the clues to recognising plain film radiographs?

Answer 14

• Multiple superimposed bones
• Soft tissue is grey
• Air is black

Question 15

What are the clues to recognising CTs?

Answer 15

• White circle of skull
• Black CSF in sulci and ventricles. Air is black
• Grey brain with subtle grey-white difference
• Image quality: reconstructed by back projection from rotating fan beam of X-rays. Beam hardening from radio dense objects
• Metal produces white starburst artefacts
• Slightly grainy

Question 16

What are the clues to recognising MRIs?

Answer 16

• White CSF is the best clue, but only true for T2-weighted MRI
• Same anatomy with different sequences often shown
• Better grey-white matter differentiation than CT
• The skull is a thin black circle, immediately surrounded by a white circle of subcutaneous fat
• Image quality: reconstructed from Fourier transforms of radio signals
• Has a JPEG like quality, usually not grainy

Question 17

What are the clues to recognising PETs?

Answer 17

• Images often have bright and varied colour

- The image is fuzzy

Question 18

What are the clues to recognising US?

Answer 18

• Wedge-shaped image with the edges of the image diverging away from top to bottom
• Often has a curve at the top matching the ultrasound probe (exception: flat probes)
• Noisy image
• Objects which block the ultrasound beam (air, bone, stones) casts shadows cast downwards

Question 19

What are the advantages of plain radiographs?

Answer 19

• Almost universal availability
• Fast
• Sequential images in subtraction angiography

Question 20

What are the disadvantages of plain radiographs?

Answer 20

Lacks soft tissue detail

Question 21

What are the advantages of ultrasound?

Answer 21

• No radiation
• Less expensive
• Can be performed in the neonatal unit
• Movement tolerant

Question 22

What are the disadvantages of ultrasound?

Answer 22

• Requires a wide enough open fontanelle (up to about 1 year)
• Image quality and interpretation based on operator skill

Question 23

What are the advantages of CT?

Answer 23

• Rapid
• Metal and pacemaker tolerance
• Good for demonstrating acute haemorrhage

Question 24

What are the disadvantaged of CT?

Answer 24

• Radiation 2mSv

- More expensive cumbersome equipment

Question 25

What are the advantages of radionuclide imaging?

Answer 25

Physiological information

• Glucose metabolism
• Perfusion
• Dopamine reuptake receptors

Question 26

What are the disadvantages of radionuclide imaging?

Answer 26

• Unclear anatomical information
• Medium cost of equipment
• Radiotracers can be very expensive

Question 27

What are the advantages of MRI

Answer 27

• No radiation
• Soft tissue differentiation
• Physiological information
  
  • Blood flow
  • Diffusion restriction
  • Metabolite concentrations

Question 28

What are the disadvantages of MRI?

Answer 28

• Poor tolerance of metalwork
• Magnetic sensitive electronics may fail or are contraindicated (Pacemakers, Cochlear implants absolutely)contraindicated
• Least movement tolerance
• Slow, must limit sequences
• Most expensive equipment
• Danger of metallic objects becoming projectiles

Question 29

What are the relative contraindications for MRI?

Answer 29

• Claustrophobia
• Pregnancy
• Tattoos