DWI, perfusion, SWI in stroke Flashcards

1
Q

what are flow abormalities in acute ischaemic stroke

A

macrovacular : large vessel occlusion

microvascular: reduced tissue perfusion

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2
Q

what happens in cellular dysfunction

A

flow 10-15ml/mi

swelling of neurons: cytotoxix oedema

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3
Q

what happens after the structure breakdown after 6 hours

A

damage to BBB. neurons more susceptible to ischaemic than endothelial
fluid leaks into extracellular space: vasogenic oedema

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4
Q

what sequences can you do in hyperacute stroke

A

DWI, T2*, SWI, FLAIR, MRA, MRperfusion

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5
Q

why is DWI useful in stroke

A

highly sensitive to acute ischaemia
DWI lesion not always irreversible
lesion volume good prognostic indicators of risk of haemorrhagic transformation, 90 day FLAIR volume
DWI changes in haemorrhage

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6
Q

is dwi/adc bright/dark on acute/chronic

A

acute: dwi bright, adc dark

chronic, dwi dark, adc bright

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7
Q

what are PWI technqiues

A

looks at imaging blood flow, inject contrast medium take rapid series of images, time signal intensity curves
CT perfusion
dynamic susceptibility contrast - t2*w first pass bolus imaging
arterial spin labeling

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8
Q

which diseases are pwi indications in cerebrovascular disease

A

acute ischaemic stroke - eliminate patients who don’t benefit from thrombolysis, expand time window for patients who may benefit from thrombolysis
transient IA
carotid stenosis
intracranial arterial stenoses - moyamoya disease, vasculities, artheroma

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9
Q

what can you see on CT perfusion in RT MCA occlusion

A

caudate nucleus on one side but absent on other

cortex preserved

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10
Q

how do you do dynamic susceptibility contrast mr perfusion imaging and what do you see?

A

rapid i.v.bolus injection of a contrast agent
rapid series of t2*w GRE
-something becomes darker in brain - blood vessels
occlusion of carotid artery

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11
Q

what is the central volume theorem

A

height of bolus corresponds to cerebral blood flow. area under curve is cerebral blood volume.
MTT= area/height of the tissue residue function R(t)
MTT=CBV/CBF

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12
Q

what do you do if you have prolongation of MTT

A

to maintain - increase blood volume or increase oxygen extraction

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13
Q

how to do deconvolution - bolus and cbf

A

measure input function in artery that is proximal to tissue target, then do deconvolution method that gives right CBF

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14
Q

what happened in DEFUSE study

A

looked at mismatched/no mismatch profile for ASL in stroke evolution
some did not benefit with iv thrombolysis

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15
Q

what was the outcome with fatal intracranial haemorrhage for DEFUSE malignant

A

not good

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16
Q

if there is perfusion abnormality on tmax or cbf maps in TIA, what to do?

A

increase tmax so longer for blood to arrive, cbf normal, then basal dilation?

17
Q

what happens in ASL

A

hydrogen approaches brain then have inversion pulse. in the end can see how long it takes for it to reach target tissue then do control experiment.

non-inverted arterial spins go to brain. 180 rf pulse. become inverted spins. blood tissue water exhange. take multiple acquisitions

18
Q

what happens in arterial transit artefact on ASL

A

serpinginous high signal on surface of brain. labeled blood that has not yet reached the capillary bed
att > post labeling delay

19
Q

what does t2*/swi detect in stroke

A
haemorrhage
cerebral microbleeds
superficial siderosis
hypo-intense vessel sign
venous 'brush sign'