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c2 modules clinical > Perfusion, Diffusion and SWI > Flashcards

Perfusion, Diffusion and SWI Flashcards

1
Q

What are the Acute Ischaemic Stroke Pathophysiology?

A
  1. Flow abnormalities
    - Monovascular level: large vessel occlusion
    - Microvascular level: Reduced tissue perfusion
  2. Cellular dysfunction
    - flow 10-15ml/100g/min
    - swelling of neurons: cytotoxic oedema
  3. Structural breakdown (after 6 hours)
    - damage to BBB
    - fluid leaks into extracellular space: vasogenic oedema
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2
Q

What are the sequences for Hyperacute Stroke?

A
  1. DWI
  2. T2*/SWI
  3. FLAIR
  4. MRA
  5. MR Perfusion?
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3
Q

DWI

A

if there is cytotoxic oedema and the neurons swell, bottom moves much more difficult in the extracellular space –> restricted diffusion

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4
Q

Restricted diffusion

A

Appears bright on DWI

Appears dark on ADC map

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5
Q

What are features of DWI?

A
  1. Highly sensitive to acute ischaemia
  2. DWI lesion not always irreversible
  3. DWI lesion volume good prognostic indicators of:
    - risk of haemorrhagic transformation
    - risk of malignant MCA infarction
    - 90 days FLAIR infarct volume (24h DWI)
  4. DWI changes in haemorrhage
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6
Q

What is ADC map a true measure of?

A

Water movement

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7
Q

What is important to do?

A

Distinguish acute from chronic infarcts

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8
Q

Acute infarct

A

DWI: bright
ADC: dark

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9
Q

Chronic infarct

A

DWI: dark
ADC: bright

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10
Q

What can be observed on a CT?

A

Acute stroke will not appear so dark

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11
Q

What happens if you have stroke on 2 different territories?

A

Think of embolic or vasculitis

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12
Q

What is vasculitis?

A

Inflammation of the blood vessels

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13
Q

How do you predict the malignant MCA infarction?

A
  1. Whether DWI volume was greater than 82 ml
  2. Whether there was a clinical scale NHIS
  3. Whether there was an occlusion in the mamogram
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14
Q

DWI-FLAIR Mismatch

A

If the FLAIR becomes positive - likely to be older than 4.5 hours

if the FLAIR is largely negative - a very recent infarct

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15
Q

what are the features of oedema in the acute stroke?

A
  1. Cytotoxic
  2. Cellular swelling
  3. Restricted diffusion
  4. if older - Vasogenic odema
  5. Restricted diffusion - a week to 10 days - normalizes
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16
Q

What is PWI good for?

A

Looking at hyperacute stroke

Directly looking at the blood flow

17
Q

How can you look at the blood flow?

A
  1. Inject a contrast medium
    - CT iodinated
    - MR gadolinium
  2. Take rapid series of images
  3. Look at time sequences on intensity curve
18
Q

What is Arterial Spin Labelling?

A
  1. Doesn’t need an injection of a contrast medium
  2. Labels endogenous hydrogen molecules in carotid arteries
  3. Look at how quickly spins recover
  4. Measure perfusion
19
Q

What is the pnemumbra?

A

Tissue that is endangered but not infarcted yet

20
Q

MR perfusion

A

Inject gadolinium

First pass: Gadolinium goes to the brain - expect a signal drop

21
Q

What is the Central Volume Theorem?

A
  1. Height of the bolus corresponds to the CBF
  2. Area under the curve is the CBV
  3. MTT - is the area divided by the height
22
Q

What is the equation for the Central Volume Theorem?

A

MTT = CBV/CBF

CBF = CBV/MTT

23
Q

How can you increase the blood volume?

A
  1. Vasodilation

2. Collaterals

24
Q

What does the convolution method give?

A

Gives the correct CBF

Select an input function

25
Q

PWI to extend time window

A

Tmax of > 6 seconds
Infarct size < 70 ml
Perfusion lesion/infarct vol > 1.8
Benefit from stroke treatment

26
Q

What do you look for in the mismatch?

A

Tissue where the blood takes longer to arrive than usual

27
Q

TIA

A

Do not show diffusion abnormality

Resolves within 24 hours

28
Q

Patients with TIA symptoms

A

If diffusion was abnormal - 2 patterns:

  1. Increase in Tmax - takes longer for the blood to arrive
  2. Cerebral blood flow was normal
  3. There is vasodilation/some collaterals
29
Q

What is Crossed Cerebellar Diaschisis (CCD)

A

If you have abnormality or hyperperfusion in one of the cerebral hemispheres - contralateral cerebral hemisphere - complicated neurogenic depression mechanism

30
Q

What is Moyamoya disease?

A

Non vasculitic, non-artherosclerosis occlusion of the terminal carotids

  • No inflammation
  • Ideopathic
31
Q

What is EC-IC Bypass?

A

A surgical procedure to increase cerebral blood flow

32
Q

What are the 2 mechanisms of stroke?

A
  1. Embolic - abnormalities in DWI

2. Haemodynamic

33
Q

What is Deoxyhaemoglobin?

A

Paramagnetic

c2 modules clinical (26 decks)

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