CT Angiography (CTA) Brain: Diagnostic Applications and Capabilities
CT angiography (CTA) of the brain is primarily used to detect and evaluate vascular abnormalities including aneurysms, arteriovenous malformations, arteriovenous fistulas, vascular stenosis, occlusions, and dissections.
Primary Applications of CTA Brain
- Detection of cerebral aneurysms with sensitivity >90% for aneurysms, though sensitivity decreases for aneurysms <3mm in size or those adjacent to bone 1
- Evaluation of arteriovenous malformations (AVMs) with 90% sensitivity for overall detection, 100% for AVMs >3cm, and 88% for associated flow-related aneurysms 1
- Assessment of arteriovenous fistulas (AVFs) with 86% sensitivity and 100% specificity in patients with pulsatile tinnitus 1
- Post-treatment surveillance of previously treated aneurysms and vascular malformations, though limited by metallic streak artifacts from coils, clips, or stents 1
- Evaluation of suspected vascular injury following trauma with sensitivity of 97.7% and specificity of 100% compared to catheter angiography 1
Advantages of CTA Brain
- Fast and noninvasive imaging technique compared to conventional catheter angiography 1, 2
- High spatial resolution allowing detailed visualization of vascular anatomy 1
- Widely available in most emergency settings 3
- Can be performed quickly in acute settings such as suspected stroke or subarachnoid hemorrhage 2
- Provides cross-sectional imaging that helps in treatment planning 4
Limitations of CTA Brain
- Limited sensitivity for small aneurysms (<3mm) or those adjacent to osseous structures 1
- Requires intravenous contrast which may be contraindicated in patients with renal dysfunction or contrast allergies 2
- Involves radiation exposure, which is a consideration especially for follow-up imaging 2
- Limited by metal artifacts from previously placed coils, clips, or stents during follow-up imaging 1
- Lacks temporal resolution compared to catheter angiography, though 4D-CTA techniques are improving this limitation 3, 4
Comparison with Other Modalities
- Catheter angiography (DSA) remains the gold standard with highest spatial and temporal resolution but is invasive with potential complications 1
- MRA has comparable sensitivity (95%) and specificity (89%) to CTA for aneurysm detection but with no radiation exposure 1
- CTA is superior to MRA for evaluating patients with clipped aneurysms due to less susceptibility to metal artifacts 2
- MRA is superior to CTA for evaluating patients with coiled aneurysms due to less metal artifact 2
Clinical Algorithms for CTA Brain Use
- For suspected subarachnoid hemorrhage: Begin with non-contrast CT head to detect hemorrhage, followed by CTA if hemorrhage is present 2
- For unruptured aneurysm surveillance: CTA or MRA are appropriate, with choice based on patient-specific factors 1
- For high-risk screening (e.g., patients with ADPKD or family history): MRA is preferred due to lack of radiation exposure 1
- For post-treatment surveillance: Choice between CTA and MRA depends on treatment type (clips vs. coils) 1
Emerging Applications
- 4D-CTA (time-resolved CTA) provides dynamic information similar to DSA but non-invasively, improving evaluation of flow dynamics in vascular malformations 3, 4
- CT perfusion with CTA can help in stroke evaluation by assessing both vessel occlusion and tissue perfusion 3
CTA brain has revolutionized the non-invasive evaluation of cerebrovascular disease, providing detailed vascular imaging with high diagnostic accuracy for most clinical applications.