Neuroradiology

Question 1

List five reasons to indicate to perform a CT scan

Answer 1

• Head trauma
• Acute stroke
• Headache: red flags for suspected tumour or subarachnoid haemorrhage
• Cancer: looking for metastatic brain tumours in patients with symptoms
• Post-surgical: hydrocephalus, haemorrhage

Question 2

What are reasons not to perform a CT scan?

Answer 2

• Minor head trauma exclusion criteria
• Seizure
- Primary idiopathic generalised epilepsy
- Complete recovery after a first seizure is not epilepsy

Question 3

List seven indications to perform an MRI scan

Answer 3

• Demyelination (diagnose MS)
• CNS tumours
• Spine – for intervertebral disc prolapse
• Transient ischaemic attacks • Epilepsy
• Paediatric neurology
• Headache (benign intracranial hypertension)

Question 4

What are contraindications to perform an MRI scan?

Answer 4

Implanted electronics:
• Most cardiac pacemakers, implantable defibrillators, cochlear implants
• Relative contraindication for programmable shunts, insulin pumps

Moveable metallic implants:
• Aneurysm clips, heart valves, recent intra-abdominal clips

Relative contraindications:
• Claustrophobia, pregnancy, tattoos

Question 5

List four neurological pathologies that angiography can diagnose

Answer 5

Large vascular abnormalities:
• Aneurysm
• Arteriovenous malformation 
• Carotidocavernous fistula 
• Unstoppable epistaxis

Question 6

What is perfusion?

Answer 6

The volume of blood passing through a defined volume of tissue per unit time (ml/100g tissue/min)

Can be a CT or MRI technique

Question 7

Name two disorders of abnormal perfusion seen with CT perfusion

Answer 7

• Stroke - decreased perfusion

* Tumour - increased perfusion indicated angiogenesis and a more aggressive tumour

Question 8

What is the use to PET scans?

Answer 8

PET is used to map out glucose usage

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

Question 9

Name three pathologies which involve increased metabolism of glucose which can be seen on a PET scan?

Answer 9

• Tumour
• Inflammation
• Infection

Question 10

Name some features of plain radiographs

Answer 10

• Multiple superimposed bones, bones are white
• Soft tissue is grey
• Air is black

Question 11

What are features of CT scan?

Answer 11

• White circle of skull
• Black CSF in sulci and ventricles. Air is black.
• Grey brain with subtle grey-white matter difference

Question 12

What are the features on an MRI scan?

Answer 12

• Better grey-white matter differentiation than CT

* Skull is a thin black circle, immediately surrounded by a white circle of subcutaneous

Question 13

What are the features of a PET scan?

Answer 13

• Images often have bright and varied colours

* Fuzzy image

Question 14

What are the features of an ultrasound scan?

Answer 14

• 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)
• Objects which block the ultrasound beam (air, bone, stones) cast shadows cast downwards

Question 15

What are the advantages and disadvantages of plain radiographs?

Answer 15

Advantages:
• Universal availability
• Fast
• Sequential images in subtraction angiography

Disadvantages:
• Lack soft tissue detail

Question 16

What are the advantages and disadvantages of ultrasound scans?

Answer 16

Advantages:
• No radiation
• Less expensive equipment
• Movement tolerant

Disadvantage:
• Requires wide enough open fontanelle
• Image quality and interpretation based on operator skill

Question 17

What are the advantages and disadvantages of CT scans?

Answer 17

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

Disadvantages:
• Radiation
• More expensive equipment

Question 18

What are the advantages and disadvantages of radiology?

Answer 18

Advantages
Physiology info:
• Glucose metabolism 
• Perfusion 
• Dopamine reuptake receptors

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

Question 19

What are the advantages and disadvantage of MRI?

Answer 19

Advantages: 
• No radiation 
• Soft tissue differentiation 
• Physiological info:
- Blood flow 
- Diffusion restriction 
- Metabolite concentrations 

Disadvantages:
• Poor tolerance of metalwork
• Magnetic sensitive electronics may fail or are contraindicated; pacemakers, cochlear implants
• Least movement tolerance
• Most expensive equipment
• Danger of metallic objects becoming projectiles