Neuroradiology Flashcards
Advantages of ultrasound (4)
No radiation
Less expensive equipment
Can be performed in the
neonatal unit
Movement tolerant
Disadvantages of ultrasound (2) one is neuro related
Neuro related: Requires a wide
enough open fontanelle
i.e. up to about 1 year of
age
Image quality and
interpretation based on
operator skill
Advantages of plain radiographs ie x-rays (3)
Almost universal
availability
Fast
Sequential images in
subtraction angiography
Advantages of CT imaging (3)
Rapid
Metal and pacemaker tolerance
Good for demonstrating acute haemorrhage
Disadvantage of x-ray imaging (1)
lacks soft tissue detail
Disadvantages of CT scans (2)
Radiation - 2 msv
more expensive, heavy/large equipment
Advantages of Radionuclide radiology
Gives you physiological information: • Glucose metabolism • Perfusion • Dopamine reuptake receptors
Disadvantages of radionuclide radiology
Unclear anatomical
information
Medium cost of equipment
Radiotracers can be
expensive
Advantages of MRI (3)
No radiation
Soft tissue differentiation
Physiological information: • blood flow • diffusion restriction • metabolite concentrations
Disadvantages of MRI (6)
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 some important neurological emergencies needing urgent imaging? (4)
trauma
acute stroke
cauda equina compression
subarachnoid haemorrhage
How do you identify an ultrasound scan? (2)
Wedge-shaped image with the edges of the image
diverging away from top to bottom
Objects which block the ultrasound beam (air, bone,
stones) cast shadows downwards
noisy image
How do you identify radionuclide radiology/ nuclear medicine/PET?
images often have bright and varied colours
image is fuzzy
How do you identify an MRI scan
White CSF is the best clue, but only true for T2-
weighted MRI
Better grey-white matter differentiation than CT
Image quality - has a JPEG-like quality, usually not grainy
How do you identify a CT scan
White circle of skull
Black CSF in sulci and ventricles. Air is black.
Grey brain with subtle grey-white matter difference
Metal = white
Why do we do PET scans
PET is usually used to map out glucose usage
Increased metabolism is seen in:-
• Tumour
• Inflammation
• Infection
Useful after brain tumour resection for differentiating
granulation tissue (low energy usage) from leftover
tumour (high energy usage).
Why do we do CT perfusion scans? (although not common)
Perfusion is defined as the volume of blood passing
through a defined volume of tissue per unit time
Disorders of abnormal perfusion
• Stroke – decreased perfusion
• Tumour – increased perfusion indicates angiogenesis
and a more aggressive tumour
Uses of angiography in the diagnosis of neurological pathology?
Large vascular (arterial and venous) abnormalities
Diagnosis and treatment of:-
- Aneurysm
- Arteriovenous malformation
- Carotid-cavernous fistula - abnormal connection between an artery in your neck and the network of veins at the back of your eye
- Unstoppable epistaxis (haemorrhage - bleeding nose)
Contraindications to perform MRI scan
Implanted electronics (check with manufacturer):
• Cardiac pacemakers, implantable defibrillators,
cochlear implants
• Relative contraindication for programmable shunts,
insulin pumps
Moveable metallic implants (check make and model):
• Aneurysm clips, heart valves, recent intra-abdominal
clips
Relative contraindications
• Claustrophobia, pregnancy, tattoos
Why might a neurologist request an MRI scan? (4)
– Demyelination: for example, to help diagnose multiple
sclerosis
– Epilepsy: NICE and SIGN guidelines (and if surgery is
contemplated)
– Paediatric neurology: disorders of development, head
circumference, congenital malformations
– Headache: benign intracranial hypertension
Reasons why you wouldn’t perform a CT scan
Minor head trauma
Seizure - choose MRI usually
Indications to perform a CT scan
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 - haemorrhage, hydrocephalus
Indications to perform MRI
Mostly under specialist physicians:
Epilepsy
Demyelination (MS?)
Spine (inter-vertebral disk compression with resulting neural compression)
Cancer (Number, location and aggression of brain tumours)
Paediatric neurology (Disorders of development? head circumference, congenital malformations)
Stroke
Headache (benign intracranial hypertension?)
