DWI, perfusion, SWI in stroke

Question 1

what are flow abormalities in acute ischaemic stroke

Answer 1

macrovacular : large vessel occlusion

microvascular: reduced tissue perfusion

Question 2

what happens in cellular dysfunction

Answer 2

flow 10-15ml/mi

swelling of neurons: cytotoxix oedema

Question 3

what happens after the structure breakdown after 6 hours

Answer 3

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

Question 4

what sequences can you do in hyperacute stroke

Answer 4

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

Question 5

why is DWI useful in stroke

Answer 5

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

Question 6

is dwi/adc bright/dark on acute/chronic

Answer 6

acute: dwi bright, adc dark

chronic, dwi dark, adc bright

Question 7

what are PWI technqiues

Answer 7

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

Question 8

which diseases are pwi indications in cerebrovascular disease

Answer 8

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

Question 9

what can you see on CT perfusion in RT MCA occlusion

Answer 9

caudate nucleus on one side but absent on other

cortex preserved

Question 10

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

Answer 10

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

Question 11

what is the central volume theorem

Answer 11

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

Question 12

what do you do if you have prolongation of MTT

Answer 12

to maintain - increase blood volume or increase oxygen extraction

Question 13

how to do deconvolution - bolus and cbf

Answer 13

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

Question 14

what happened in DEFUSE study

Answer 14

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

Question 15

what was the outcome with fatal intracranial haemorrhage for DEFUSE malignant

Answer 15

not good

Question 16

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

Answer 16

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

Question 17

what happens in ASL

Answer 17

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

Question 18

what happens in arterial transit artefact on ASL

Answer 18

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

Question 19

what does t2*/swi detect in stroke

Answer 19

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