CT Angiography

Overview

CT angiography (CTA) is performed by scanning the patient during a rapid IV contrast bolus infusion while the contrast is in the arterial phase. Imaging can be performed from the aortic arch through the head. Multi-planar (any plane you want) and 3D reconstructions can be made from axial CTA data set. CTA is very fast and there are few patient contraindications (contrast allergy, renal failure). If there is a clinical concern for venous pathology, delayed images may be obtained in the venous phase (CTV).

Axial (left) and parasagittal thick reformat show 70% stenosis of the right internal carotid artery just above the carotid bifurcation

CTA is often performed in patients presenting with a thunderclap headache and subarachnoid hemorrhage found on an non contrast scan. In these patients, an intracranial aneurysm is suspected and a CTA is the fastest modality to establish a diagnosis.

Axial (left), thick coronal reconstruction (middile), and 3D rendering of a head CTA illustrate a basilar artery tip aneurysm.

CT Perfusion

CT perfusion (CTP) can be performed in conjunction with CTA. CT perfusion provides information regarding the transit time of blood to the brain, flow rate to the brain, and volume of blood being delivered to the brain. This information is crucial in evaluation of vascular stenosis or stroke. It can also be useful in other applications such as tumor imaging.

CT perfusion shows prolonged transit time (red on left image) to the left hemisphere, decreased blood flow to the left hemisphere (blue on middle image), and symmetric blood volume (right image). This could be seen in the context of left internal carotid artery stenosis limiting perfusion in the left middle and anterior cerebral artery territories.

Indications

  • Vascular stenosis/occlusion
  • Aneurysm evaluation
  • AVM/AVF

Advantages

  • Fast
  • Look at vessels and surrounding soft tissues

Disadvantages

  • Radiation
  • Need contrast
  • Expensive
  • Calcification may overestimate stenosis