Computed Tomography Angiography of Cerebral Arteries

Computed Tomography Angiography (CTA) of Cerebral Arteries

• CTA of the cerebral arteries, also known as a CTA carotids or arch-to-vertex angiogram, is a non-invasive technique visualising internal and external carotid arteries and vertebral arteries.
• Computerized tomographic angiography visualises blood vessels after contrast medium injection.
• This includes the Circle of Willis and carotid arteries.

CTA of Cerebral Arteries: Head and Neck

• Angiogram of the head is used to study the Circle of Willis.
• Also known as cerebral angiography.
• Neck angiography studies carotid arteries.
• Also known as carotid angiography.

CTA Preparation

• Patients are NPO (nothing by mouth) for 3-4 hours before the exam.
• Patients must not have severe allergies or asthma.
• Recent renal function tests (RFT) must be normal.
• Procedure must be explained to the patient.
• Signed consent form is required.
• Sedation is given if needed.

CTA: Circulation

• Extracranial Circulation: Includes atherosclerosis, aneurysms, and dissections.
• Intracranial Circulation: Includes intracranial aneurysms and arteriovenous malformations.

CT Scanning Position

• Patient position is supine with arms by their side for cervicocranial artery scanning.
• Right antecubital vein is preferred for access.

Arterial Supply of the Brain

• Blood supply to the brain comes from two arteries:
  • Internal carotid artery
  • Vertebral artery.
• These arteries and their branches arise in pairs supplying both sides of the brain.
• Major arteries (basilar and internal carotid) interconnect at the base of the brain to form the circle of Willis (a six-sided polygon).
• The circle of Willis is around the interpeduncular fossa.

Cerebral Circulation Diagram

• Shows the complex branching network of arteries.
• Includes detailed labels like anterior cerebral artery, middle cerebral artery, internal carotid artery, anterior choroidal artery, posterior cerebral artery, pontine arteries, basilar artery, vertebral artery, and others.

CTA Indications

• Aneurysms
• Narrowing of arteries in the brain
• Abnormal blood vessels
• Narrowing or blockage of carotid arteries (stenosis)
• Determine future stroke risk
• Carotid artery strictures

CTA Contraindications

• Pregnancy
• Allergy to contrast media
• Weak kidney function
• Unstable vital signs

CTA Technique Summary

• Patient position: supine with arms by the side.
• Scout scan: mid-chest to vertex.
• Scan extent: aortic arch to vertex.
• Scan direction: caudocranial.
• Contrast injection monitoring slice: descending aorta
• Threshold: 150 HU
• Contrast injection: 50-75 ml non-ionic iodinated contrast with 50 ml saline.
• Scan delay: minimal
• Respiration: suspended during the scan.

CTA Post-Processing

• CTA images are usually presented as axial, coronal and/or sagittal multiplanar reformat.
• Additional techniques: Maximum Intensity Projection (MIP) displays pixels with higher CT value.
• Curved planar reformats: Shows the entire course of tortuous vessels.

Case Examples

• Residual aneurysm in the left posterior communicating artery (PCOM).
• Aneurysm in the anterior cerebral artery.

This quiz covers the principles and techniques of Computed Tomography Angiography (CTA) for cerebral arteries. It includes preparation protocols, examination of the Circle of Willis, and the significance of different carotid arteries. Test your knowledge on this non-invasive imaging modality used in neurology.