Stroke imaging has evolved from plain CT to advanced vascular and perfusion studies. CT Angiography (CTA) is now a cornerstone in the evaluation of acute ischemic stroke, guiding reperfusion therapy and prognostication.
📌 Why CT Angiography in Stroke?
- Rapid, widely available, and performed immediately after non-contrast CT.
- Detects large vessel occlusion (LVO) for thrombectomy eligibility.
- Identifies stenosis, dissection, atherosclerotic plaque, aneurysm, AVM.
- Maps collateral circulation – important for predicting infarct growth.
⚙️ Technique
- Performed after non-contrast CT (NCCT) brain.
- Bolus IV contrast injection (60–80 mL at ~4–5 mL/sec).
- Scan from aortic arch → vertex to cover extracranial and intracranial vessels.
- Post-processing: MIP, MPR, 3D VR reconstructions.
🔍 CTA Findings in Stroke
1. Arterial Occlusion
- Abrupt cutoff or non-opacification of artery (ICA, MCA, ACA, PCA, basilar).
- “Hyperdense MCA sign” on NCCT corresponds to clot → confirmed on CTA.
2. Stenosis / Dissection
- Narrowing, tapering (“string sign”), intimal flap, double lumen.
3. Collateral Status
- Good collaterals = smaller infarct core, better thrombectomy outcomes.
- Poor collaterals = rapid infarct expansion.
4. Other Findings
- Carotid atherosclerotic plaque or ulceration.
- Tandem lesions (cervical ICA + intracranial occlusion).
- Vascular anomalies (persistent trigeminal artery- persistent connection between the internal carotid artery and the basilar artery ; fenestrations).
🩺 Role in Stroke Workflow
- NCCT → Rule out hemorrhage.
- CTA → Detect LVO, stenosis, dissection, aneurysm.
- CT Perfusion (if available) → Differentiate infarct core vs penumbra.
- Treatment decision → Thrombolysis (<4.5 hrs) ± Mechanical Thrombectomy (<24 hrs if LVO + favorable imaging).
📌 Teaching Pearls
- CTA is essential before thrombectomy – identifies LVO and access route.
- Look for “dense vessel sign” on NCCT → confirm with CTA.
- Always assess extracranial + intracranial circulation.
- Evaluate collateral flow (leptomeningeal vessels).
