BrainLive data

CT Perfusion — Acute Stroke

CT perfusion (CTP) is a dynamic contrast-enhanced technique that quantifies cerebral haemodynamics in acute ischaemic stroke. By deriving cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and time-to-maximum (Tmax), it distinguishes infarct core from salvageable penumbra and, with automated software, informs thrombectomy eligibility in extended windows.

Indications

Acute anterior-circulation large-vessel occlusion for thrombectomy selection in the 6-24 hour window
Stroke with unknown time of onset (e.g. wake-up stroke) requiring tissue-based selection
Confirmation and quantification of ischaemic penumbra beyond standard treatment windows
Problem solving in suspected stroke mimics and posterior circulation ischaemia

Contraindications & Cautions

Severe iodinated contrast allergy without adequate premedication
Significant renal impairment (weigh urgency of reperfusion decision against risk)
Established large infarct on non-contrast CT where perfusion adds little
Haemorrhage on non-contrast CT (perfusion not indicated as first test)

Patient Preparation

Preceding non-contrast head CT to exclude haemorrhage and large established infarct
Secure large-bore intravenous access (18-20 G) for power injection
Rapid renal function assessment per institutional acute stroke protocol
Head immobilisation to minimise motion during the dynamic acquisition

Technique & Parameters

Bolus of 35-50 mL iodinated contrast at 4-6 mL/s followed by saline flush
Dynamic cine acquisition (typically 45-70 seconds) with adequate temporal sampling to capture first pass
Coverage of the vascular territory of interest (whole-brain coverage where available)
Post-processing with deconvolution to generate CBF, CBV, MTT and Tmax parametric maps
Automated software (e.g. RAPID) for core and penumbra volumetrics and mismatch calculation

Systematic Review

Verify arterial input and venous output functions and adequacy of the bolus
Inspect CBF and Tmax maps for the region of hypoperfusion
Define core as relative CBF <30% and penumbra as Tmax >6 s
Compute mismatch volume (penumbra minus core) and mismatch ratio
Correlate with CT angiography occlusion site and non-contrast CT

Key Findings & Significance

Ischaemic core: markedly reduced CBF (rCBF <30%) with matched reduced CBV
Penumbra: prolonged Tmax >6 s with preserved or increased CBV (autoregulation)
Prolonged MTT and Tmax delineating the total ischaemic territory
Favourable mismatch profile (e.g. core <70 mL, mismatch ratio ≥1.8, mismatch volume ≥15 mL)
Luxury perfusion or reperfusion hyperaemia after recanalisation

Differential Considerations

Seizure-related hyperperfusion or postictal hypoperfusion mimicking ischaemia
Chronic small-vessel ischaemia and prior infarct causing baseline perfusion asymmetry
Migraine aura with cortical spreading hypoperfusion
Technical artefact from poor bolus, motion or truncated acquisition
Venous or watershed hypoperfusion unrelated to acute large-vessel occlusion

Pearls & Pitfalls

CTP thresholds are software and processing dependent; use validated, consistent parameters
Core volume can be overestimated in the very early time window (ghost infarct core)
Always interpret CTP alongside non-contrast CT and CT angiography, never in isolation
DEFUSE 3 and DAWN trial criteria underpin extended-window thrombectomy selection

Structured Report

Report ischaemic core and penumbra volumes and the mismatch ratio
State the occlusion site correlated with CT angiography
Comment on whether the profile meets institutional thrombectomy criteria
Note technical adequacy and any confounders (motion, bolus timing)
Provide an integrated conclusion combining CT, CTA and CTP findings

References

Albers GW et al. DEFUSE 3: Thrombectomy for Stroke with Perfusion-Imaging Selection, NEJM
Nogueira RG et al. DAWN: Thrombectomy 6 to 24 Hours after Stroke with Clinical-Infarct Mismatch, NEJM
Radiographics: Vagal A et al. Automated CT Perfusion Imaging for Acute Ischemic Stroke
AHA/ASA Guidelines for the Early Management of Patients with Acute Ischemic Stroke

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

CT Perfusion — Acute Stroke

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References