Synopsis
Choose and interpret emergency neuroimaging according to the clinical decision, understanding what non-contrast CT, angiography, perfusion and MRI sequences can and cannot establish.
- Order an examination to answer a decision, not merely 'CT head'. State onset, deficit, trauma, cancer, infection, anticoagulation, pregnancy, renal function, implants and the suspected anatomical level.
- Non-contrast CT is fast and excellent for acute blood, skull injury, hydrocephalus and major mass effect, but early ischaemia, posterior-fossa disease, encephalitis and diffuse axonal injury may be subtle or absent.
- CT angiography maps arterial lumen and is central to detecting large-vessel occlusion, aneurysm and some dissections; its urgency is driven by reperfusion or haemorrhage decisions.
Key red flags
Fresh blood is usually hyperdense on non-contrast CT, with location suggesting intraparenchymal, subarachnoid, subdural or extradural compartments. Density evolves with time and severe anaemia can reduce conspicuity.
Investigation priorities
Rapidly identify acute blood, mass effect, hydrocephalus, major infarction, fracture and some stroke mimics.
Management branches
Sudden disabling focal deficit or posterior-circulation syndrome within a potential thrombolysis or thrombectomy pathway.
- Activate the stroke team, establish last known well, glucose, deficit severity, anticoagulation and baseline function and proceed to urgent non-contrast CT without avoidable ward-based delay.
- Acquire CTA and perfusion or MRI according to local pathway, onset and thrombectomy criteria; communicate renal, contrast and device information without allowing routine tests to obstruct time-critical imaging.
Key medicines
Iodinated CT contrast mediumRadiology selects the agent, concentration, injection rate and volume for the protocol, adjusting the plan to body habitus, vascular timing, kidney function and immediate diagnostic need.
Gadolinium-based MRI contrast agentUse only the radiologist-selected product and weight-based protocol when enhancement materially answers the question; record the exact agent and administered amount in the imaging record.