Table 1.

Uses and pitfalls of imaging techniques in acute ischaemic stroke^35,36

Technique	Uses/benefits	Pitfalls
Non-contrast CT head	Widely available and quick to perform	Low sensitivity (39%) for ischaemia, especially in posterior fossa
	High sensitivity for acute haemorrhage
	Specificity of 100% if ischaemia detected
CT angiogram	Non-invasive assessment of intracranial and extracranial circulation	Unreliable in differentiating stroke from mimic (only a minority of strokes will have large artery occlusion)
	Can confirm large vessel occlusion to guide clot retrieval strategies in patients with high NIHSS scores
Diffusion-weighted magnetic resonance imaging	Abnormalities on diffusion-weighted sequences strongly support diagnosis of stroke	Restricted diffusion can be seen in tumours, cerebral infections and following seizure activity
	Sensitivity for detection of acute stroke up to 99% with specificity of 92%	Patient instability and claustrophobia can limit suitability of scan
		Requires more time for scanning than CT