Neuroradiology Flashcards
list indications to perfomr a ct scan
Head trauma: NICE guidelines Acute stroke: NICE guidelines
Headache: SIGN guidelines, red flags for suspected tumour or subarachnoid haemorrhage
Cancer: looking for metastatic brain tumours in patients with symptoms
Post-surgical: hydrocephalus, haemorrhage Flexible, common-sense, happy to discuss
what are the reasons not to perform a CT scan?
Minor head trauma exclusion criteria: NICE and SIGN guidelines
– primary idiopathic generalised epilepsy – no imaging – complete recovery after a first seizure is not epilepsy
•
Seizure: NICE guidelines (pg 16), usually choose MRI
I suggest that the detail in guidelines are not fair game for exams and that guidelines may change by the time you qualify
– Do be aware that guidelines exist for these conditions
list indications to perform MRI
Neurologists
Epilepsy: NICE and SIGN guidelines (and if surgery is contemplated)
Demyelination: for example, to help diagnose multiple sclerosis
Paediatric neurology: disorders of development, head circumference, congenital malformations
Headache: benign intracranial hypertension
Surgeons
Cancer: clarifying the number, location and aggressiveness of brain tumours
Spine: Intervertebral disc degeneration causing neural compression
contraindications to perform an 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
uses of angiography
Large vascular (arterial and venous) abnormalities Diagnosis and treatment
- Aneurysm
- Arteriovenous malformation
- Carotidocavernous fistula 4. Unstoppable epistaxis
what are the uses of CT perfusion?
Stroke – decreased perfusion
Tumour – increased perfusion indicates angiogenesis and a more aggressive tumour
what are the uses of PET scan?
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).
characteristics of a plain radiograph?
Plain radiographs • • • • Multiple superimposed bones, bones are white Immediately recognisable body parts Soft tissue is grey Air is black
characteristics of CT scan?
White circle of skull
Black CSF in sulci and ventricles. Air is black. Grey brain with subtle grey-white matter difference Image quality:
– reconstructed by back projection from a rotating fan beam of X-rays
– beam hardening from radiodense objects • Metal produces white starbust artefacts
– slightly grainy
characteristics of MRI?
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 Image quality:
– reconstructed from Fourier transforms of radio signals
– has a JPEG-like quality, usually not grainy
characteristics of an ultrasound?
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)
Very noisy image (like an old un-tuned TV)
Objects which block the ultrasound beam (air, bone, stones) cast shadows cast downwards
advantages of US
No radiation • Less expensive equipment • Can be performed in the neonatal unit • Movement tolerant
disadvantages of US
Requires a wide enough open fontanelle i.e. up to about 1 year of age
• Image quality and interpretation based on operator skillRequiresawide enoughopenfontanelle i.e. up to about 1 year of age
• Image quality and interpretation based on operator skill
advantages of plain radiograph
Almost universal availability
• Fast
• Sequentialimagesin
subtraction angiography
disadvantages of plain radiographs
lacks soft tissue detail