Neuroradiology Flashcards
CT is good at viewing what?
bony details, spatial resolution
poor soft tissue detail and contrast resolution
is CT sensitive to a bleed?
only if very recent bleed
cannot view old blood
what shows as bright white on CT?
dense materials (bone etc) less dense (e.g air) shows as black
how do grey/white matter appear on CT?
difficult to differentiate as similar density
- must view image within specific range of densities to see any difference
white matter generally darker (only on T2???)
benefits of MRI?
good contrast/soft tissue resolution
good anatomy depiction
marrow and cord pathology
multiplanar capacity
drawbacks of MRI?
less bony detail
less spatial resolution
not compatible with pacemakers and other implants (magnetic force)
not compatible with most ICU/emergency equipment
not as quick as CT, needs patient cooperation
how does MRI work?
different sequences using a combination of technical parameters
each sequence is unique and gives different information
overall MRI assessment involves correlation of all sequences
basic sequences in MRI?
T1 T2 FLAIR T2 (gradient echo) T1 (3D) volumetric contrast enhancement
what shows as bright white in T1?
fat and 4 Ms
- fat (if not purposely suppressed)
- methemoglobin (subacute hematoma)
- mineral deposition
- melanin (melanoma)
- mush (highly proteinaceous fluid)
- contrast material (gadolinium)
what shows as dark on T2?
some blood products (subacute hematoma)
mineral deposition
paucity of water or mobile protons
high flow (arterial flow voids)
bright on T2?
more water/less tissue (e.g fluid collections, oedema, demyelination, some tumours etc)
fat
dark on T1?
water
paucity of mobile protons (air, cortical bone)
high flow (arterial “flow voids”)
best imaging for a stroke?
CT (generally)
what may be seen on CT in acute stroke?
thrombosed vessel (dense area/line)
lack of grey/white matter differentiation
darker blob where fluid is accumulating after some time
stroke/infarct after some time has passed?
more fluid accumulates and density gets lower in area of brain causing it to become darker
how does infarct appear?
white on CT
imaging for haemorrhage?
CT is best but only sensitive in the initial stages
will not pick up any bleed after around 48 hours?
then an MRI will be used
how can intracranial arteries (potential aneurysms etc) be viewed?
inject contrast and then CT
SWI?
most sensitive MRI sequence for blood
susceptibility weighted imaging
clotting of dural venous sinuses?
back pressure of blood causes increased intracranial pressure
can lead to vessel rupture etc intracranially
cavernoma?
type of vascular malformation which can cause bleeding (usually not a massive bleed, can just bleed from time to time)
causes popcorn head appearance on imaging
hallmark of trauma imaging in the head?
CT
principle of trauma imaging?
skull is closed cavity with no extra space so if haematoma or swelling occurs, herniation/shifts of brain tissue will occur
extradural vs subdural haematoma?
extradural = convex shape subdural = concave shape
