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Imaging in acute stroke
Dr Samuel Gregson Radiology SpR
Radiologist?? This is a clinical diagnosis!
CT vs MRI in hyperacute stroke
- Fast acquisition (seconds vs minutes)
- Availability - Multiple scanners
- Resolution / artefacts
- Cost
- Radiation dose
CT Head: Non contrast
Unenhanced CT Head
First imaging modality used in acute stroke
Fast less than 10 seconds
Volume acquisition 1mm slices allows formatting in all planes
Infarct vs Bleed
Infarcts
Wedge shaped
Involve grey white matter junction
Loss of sulci
Anatomical to vascular distribution
Low attenuation indicated cytotoxic oedema
Haemorrhagic stroke
Most commonly secondary to hypertension
Classic anatomical areas:
Putamen, Thalamus, Pons, Cerebellum
High attenuation change with thin rim of surrounding
Oedema
Stroke mimics
Glioblastoma Mucinous metastases
Unenhanced CT
The hyperacute signs - only identified 15-60% of patients
Territories of infarct
Territories of infarct
Territories of infarct
Complications of infarct
CT Angiography (CTA)
CTA: Intracranial CT angiogram
Use of intravenous contrast to fill the intracranial arterial
vessels
May identify the thrombus within a vessel which may
guide intra-arterial thrombolysis or clot retrieval
Also evaluates the carotid and vertebral arteries of the
neck to establish the aetiology of stroke i.e.
atherosclerosis or dissection
Provides a vascular map for intervention
Left MCA M1 Branch Occlusion
Basilar tip thrombus
Vertebral artery dissection
Presented with neck pain following trauma
Vertigo, right sided hearing loss, nystagmus
Assessing carotid stenosis
Using curved planar reformats focal plaque
stenoses can be measured
CT perfusion
Becoming more established in most acute stroke centres with intervention
Important adjunct along side CT intracranial angiopathy
Differentiation of salvageable ischaemic brain tissue (penumbra) from irrevocably
infarcted brain (infarct core) - vital in assessment for thrombolysis / clot retrieval
CT perfusion
Patient with small core and large penumbra is most likely to benefit from
reperfusion therapies
Three parameters used:
1. Mean transit time (MTT) or time to peak (TTP) of deconvolved tissue residue
function (Tmax)
2. Cerebral blood flow (CBF)
3. Cerebral blood volume (CBV)
CT perfusion
Ischaemic core:
Increase mean transit time
Markedly decreased CBF
Markedly decreased CBV
CT Perfusion
Penumbra
Increased mean transit time
Moderately reduced CBF
Near normal or increased CBV
Right MCA infarct with good penumbra
MR Imaging
MRI Basic sequences
MRI Diffusion weighted sequences
Measures random Brownian motion of water molecules within a voxel of tissue
I.E. how water molecules are able to diffuse
Acute infarct - Restricted diffusion
Evolution of stroke on MRI
CT vs MRI Diffusion
Future advances?
Vascular wall imaging 3T MRI
Atherosclerosis Vasculitis
Imaging in stroke...
Vital in the early management of acute infarction
Confirms diagnosis and ensures no contraindications to treatment
Gives objective picture of infarction and possible salvageable penumbra
Aiding neurovascular intervention
Thanks! Questions?