CT Angiography of the Circle of Willis and Carotid Arteries — With or Without Intravenous Contrast
A CT imaging test that examines arteries in the brain and neck, including the Circle of Willis and carotid arteries, to evaluate blood flow and vessel abnormalities.
["This test uses CT scans to look for narrowing, blockage, or bulging of arteries supplying the brain."]
Key facts at a glance
- LOINC
- 87855-3
- Short code
- CTA Circ of Willis+Carot aa WO+W contr IV
- Synonyms
- CTA Circ of Willis+Carot aa WO+W contr IV
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ct-angio
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test?
CT angiography, or CTA, is an imaging test that creates detailed pictures of blood vessels. It may be used to examine the carotid arteries in the neck and the Circle of Willis, a network of vessels at the base of the brain.
Why might I need this test?
Your clinician may order this test to evaluate symptoms such as a sudden or one-sided headache, weakness, speech difficulty, vision changes, or dizziness. It can also be used to investigate suspected narrowing or blockage of arteries, aneurysms, or other blood-vessel abnormalities.
How is the test performed?
You lie on a CT scanner while X-ray images are taken. If the study includes intravenous contrast, a needle is placed in a vein and an iodine-based contrast medicine is injected to make the arteries easier to see.
How do I prepare for the test?
Follow your imaging center's instructions, as fasting may be requested for some studies. Tell the care team if you are pregnant, have kidney disease, or have had an allergic reaction to iodinated contrast. You may also be asked about medicines, including blood thinners or diabetes medicines.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Abnormal findings may include narrowing, blockage, or irregularity of the carotid or brain arteries, which can reduce blood flow to the brain. An artery that bulges outward may represent an aneurysm. Other findings can include abnormal vessel anatomy or signs related to an acute clot, although the results must be interpreted with your symptoms and other examinations.
Short name
CT angiography of brain and carotid arteries
Frequently asked questions
Is CT angiography a blood test?
What can CT angiography detect?
Is intravenous contrast always used?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy