Brain imaging Flashcards
What are the common imaging techniques for the brain
CT and MRI
Advantages of CT
quick, accurate, well tolerated, can enhance with contrast
good bone definition
Disadvantages of CT
radiation exposure therefore contraindicated in some eg young, pregnant
Contrast - renal impairment, hypersenstivity
Advantages of MRI
no radiation
excellent soft tissue imaging
can use contrast
many sequence patterns
Disadvantages of MRI
takes much longer
Claustrophobia
contraindicated in those with pacemakers/implants
On a CT scan, bone+blood appear black
fluid and air appear white
True or false
FALSE
Bone+blood = white
Air+fluid = black
What shape is the midbrain on a CT scan
Mickey mouse ears
What are the name of the fine gyri on the cerebellum
Folia
How does fluid appear on a MRI T1 sequence
Dark - better for seeing anatomy
How does fluid appear on a MRI T2 sequence
White - better for spotting pathology
Causes of ischaemic stroke
Embolism - cardio, paradoxical, fat, air
Atherosclerosis
Thrombosis
arterial dissection
What are the vascular territories of the brain
ACA, MCA and PCA
Reasons for imaging in stroke
Confirm infarct
Exclude haemorrhage
Rule out stroke mimics
Allow for rapid treatment
Examples of stroke mimics
Todd’s paresis (post-ictal)
tumour
1st line imaging in stroke
CT scan without contrast
Earliest characteristic sign on CT in an ischaemic stroke
Hyperdense vessel sign - thrombus in occluded vessel appears bright white
Most commonly in MCA
Imaging features of ischaemic stroke
hyperdense sign loss of grey-white matter interface cortical hypodensity parenchymal swelling and gyral effacement loss of insular ribbon (cortex) significant mass effect
normal calcified structures in the brain
pineal gland
choroid plexus
basal ganglia
falx
Describe imaging features in extradural haemorrhage
Biconvex shape
rupture of middle meningeal artery
Features of subdural haemorrhage
crescent shape (can be very subtle)
acute/chronic
rupture of bridging veins
Features of subarachnoid haemorrhage
White star sign
white (blood) in suprasellar cistern
sylvian fissures
sulci
What other investigation is done in SAH
cerebral angiography
Features of brain metastases
multiple
most common brain tumour in adults
contrast ring enhancing
LOTS of oedema and mass effect
Features of primary brain tumours
usually single
more common in children
degree of oedema depends on grade of tumour
What is 1st choice imaging in cauda equina syndrome
MRI
