Neuroradiology Flashcards
What are the common indications to perform a CT?
- Stroke
- Head trauma
- Headache
- Cancer
- Post-surgical (hydrocephalus, haemorrhage)
When may you not perform a CT scan?
- Minor head trauma exclusion criteria
- Seizure
When would a CT not be carried out for a head trauma?
- 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
What are the indications for an MRI scan?
- Epilepsy
- Demyelination
- Paediatric neurology
- Headache
- Spine degeneration
- Cancer
- Stroke
What are the contraindications to MRI scan?
- Implanted electronis such as pacemakers and cochlear implants
- Movable metallic implants such as aneurysm clips, heart valves or intrabdominal clips
What is angiography used in the diagnosis and treatment of?
- Aneurysm
- Arteriovenous malformations
- Carotidocavernous fistula
- Unstoppable epitaxis
Perfusion
The volume of blood passing through a defined volume of tissue per unit time
What techniques can be used for perfusion?
CT or MRI
What is the units of perfusion?
ml blood/100g tissue/ min
Give examples of disorders of abnormal perfusion.
- Stroke decreases perfusion
- Tumour with increased perfusion suggest angiogenesis and a more aggressive tumour
What is PET used to do?
Map out glucose usage
When can increased metabolism be seen?
- Tumour
- Inflammation
- Infection
When is PET useful?
Useful after brain tumour resection for differentiating granulation tissue (low energy use) from leftover tumour (high energy use)
What are the clues to recognising plain film radiographs?
- Multiple superimposed bones
- Soft tissue is grey
- Air is black
What are the clues to recognising CTs?
- 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
What are the clues to recognising MRIs?
- 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
What are the clues to recognising PETs?
- Images often have bright and varied colour
- The image is fuzzy
What are the clues to recognising US?
- 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
What are the advantages of plain radiographs?
- Almost universal availability
- Fast
- Sequential images in subtraction angiography
What are the disadvantages of plain radiographs?
Lacks soft tissue detail
What are the advantages of ultrasound?
- No radiation
- Less expensive
- Can be performed in the neonatal unit
- Movement tolerant
What are the disadvantages of ultrasound?
- Requires a wide enough open fontanelle (up to about 1 year)
- Image quality and interpretation based on operator skill
What are the advantages of CT?
- Rapid
- Metal and pacemaker tolerance
- Good for demonstrating acute haemorrhage
What are the disadvantaged of CT?
- Radiation 2mSv
- More expensive cumbersome equipment
What are the advantages of radionuclide imaging?
Physiological information
- Glucose metabolism
- Perfusion
- Dopamine reuptake receptors
What are the disadvantages of radionuclide imaging?
- Unclear anatomical information
- Medium cost of equipment
- Radiotracers can be very expensive
What are the advantages of MRI
- No radiation
- Soft tissue differentiation
- Physiological information
- Blood flow
- Diffusion restriction
- Metabolite concentrations
What are the disadvantages of MRI?
- 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
What are the relative contraindications for MRI?
- Claustrophobia
- Pregnancy
- Tattoos
