Carotid Imaging Flashcards
What is carotid artery?
Hardening of arteries
Where is carotid artery located?
On each side of neck pulse
What are the 3 imaging approaches?
- Anatomic criteria
- Morphological criteria
- Pathophysiological criteria
What is Grading stenosis?
All individuals with TIA or non-disabling stroke should have carotid imaging within 7 days of event or 24 hours
What are high-risk plaque features?
- Thin fibrous caps
- Intra-plaque haemorrhage
- Large lipid-rich necrotic cores
- Neurovascularisation
What did 3D TOF pulse sequence distinguish?
Between intact and thick versus thin and rupture caps
What is there 89% agreement between?
3D TOF and histology
What does contrast enhancement MRI with gadolinium demonstrate?
Preferential enhancement of fibrous tissue
What is there strong association with?
Recent and recurrent cerebrovascular event
What has some studies reported?
A moderate relationship between the degree of stenosis and likelihood of events
What can ultrasound and CT look at?
Some other plaque characteristics - is there evidence of irregularities on lining of the plaque suggestive of rupture
- there is haemorrhage within it
- Stenotic and anatomical criteria
What was the Dutch study?
Atherosclerosis is much common as you get older
- more common in men
What are the screening carotids?
- In over 80’s, moderate disease present in 7.5% of men and 5% of women
- Severe disease present in 3.1% of men and 0.9% of women
- CEA in asymptomatic individuals felt to reduce risk of stroke by 3.5% compared to best medical therapy
What are the risk of endarterectomy procedure?
region of 2-3%
What does damage within plaque cause?
Destabilisation process
Bleeding within structure itself [atherosclerotic plaque]
What is the consequence of bigger plaques?
More inflammation and more likely for the plaque to destablise
The blood can’t diffuse all the way down to the deep aspect of cord –> becomes deeper necrosis –> further inflammation
What is imaging validated against?
The endarterectomy specimen
the specimen is removed by surgery
For Fibrous cap, what is there a strong association with?
Recent and recurrent cerebrovascular events
What is plaque haemorrhage?
- Degradation of haemorrhage into methaemoglobin
- This shortens the relaxation time of T1, resulting in bright signal on T1 (such as fast-spin echo)
- Validated against histology
What is Neovascularisation?
- May be imaged using dynamic contrast-enhanced (DCE) MRI
- T1-weighted technique using repeated measurement of contrast intensity
- Post-contrast concentration and Ktrans reflect the degree of neovascularsation
Why is repeated imaging of plaque important?
To see the overall movement of gadolinium is over the course of time after the injection
What is USPIO?
- Ultrasmall supermagnetic particles of iron oxide - enhanced MRI
- These particles are taken up by macrophages via scavenger receptors
- Results in T2-weighted susceptibility effect (reduced signal)
What are the advantages of MRI?
- Excellent spatial resolution
(micrometres) - Longitudinal imaging [No radiation]
- Availability
What are the disadvantages of MRI?
- Tolerability
2. Unable to detect micro-calcification
