CT angiography of the cerebral arteries

CT angiography of the cerebral arteries (also known as a CTA carotids or an arch to vertex angiogram) is a noninvasive technique allows visualization of the internal and external carotid arteries and vertebral arteries and can include just the intracranial compartment or also extend down to the arch of the aorta. The overarching goal of this examination is an optimal enhancement of the carotid arteries with little to no venous component, the technical aspect of the examination will vary from site to site. 

NB: This article is intended to outline some general principles of protocol design. The specifics will vary depending on CT hardware and software, radiologists' and referrers' preference, institutional protocols, patient factors (e.g. allergy) and time constraints. 

CTA of the cerebral arteries is indicated in a wide variety of clinical scenarios including:

The brain is supplied by two sets of vessels. The anterior circulation roughly supplies the anterior 2/3 while the posterior circulation supplies the posterior 1/3 of the brain.

The anterior circulation consists of the carotid arteries. The right common carotid artery arises from the brachiocephalic trunk while the left common carotid artery arises directly from the aorta. They ascend behind the sternoclavicular joints, lateral to the thyroid gland and at the level of the upper border of the thyroid cartilage, each one divides into external and internal carotid arteries. The internal carotid artery ascends to enter the skull through the carotid canal and bifurcates into the anterior and middle cerebral arteries.

The posterior circulation consists of the vertebrobasilar system. Each vertebral artery arises from the 1st part of the corresponding subclavian artery. At the neck, it ascends inside the transverse foramina from C6 to C2 where it emerges and enters the cranium through the foramen magnum. Both vertebral arteries unite to form the basilar artery which passes in front of the pons and ends by bifurcation to posterior cerebral arteries on both sides.

  • patient position
    • supine with their arms by their side
  • scout
    • mid-chest to vertex
  • scan extent
    • aortic arch to vertex
  • scan direction
    • caudocranial 
    • can be performed craniocaudal to minimize venous contamination in the head portion of the scan, often utilized in slower scanners
  • contrast injection considerations
  • scan delay
    • minimal scan delay 
  • respiration phase
    • suspended 

Some centers may place a monitoring region of interest on the carotid arteries, the delay from engaging the scan to the scanner moving into its initial inferior starting point can result in a venous component. Tracking at the descending aorta attempts to maximize scan start efficiency and minimize venous interference.

Post-processing

CTA images are usually presented as axial and coronal and/or sagittal multiplanar reformat of a variety of thicknesses depending on local preference.

Additional post-processing techniques include:

CTA has a number of advantages over catheter angiography including the ability not only to evaluate the vessels from their origin at the aortic arch to the intracranial portion but also assess non-vascular neck structures and brain parenchyma. 

It is also less expensive and at lower risk to the patient.

There are few disadvantages compared to catheter angiography, however, the inability to select a single vessel and the fact that it images the vessel at only one time does limit the ability to evaluate flow-related features of complex malformations. It also has lower resolution than catheter angiography making the assessment of subtle wall changes, such as those seen in dissection or vasculitis, more difficult to identify. 

Compared to MR angiography, its main disadvantage is the need for both ionizing radiation and intravenous contrast. 

CT examinations
Share article

Article information

rID: 57590
Section: Approach
Synonyms or Alternate Spellings:
  • Arch to vertex
  • CTA of the cerebral arteries
  • CT angiography of cerebral arteries
  • CTA of cerebral arteries

Support Radiopaedia and see fewer ads

Cases and figures

  • Case 1: coronal MIP image
    Drag here to reorder.
  • Case 1: 3D volume rendering
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.