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Circle of Willis Magnetic Resonance Angiography, Without Intravenous Contrast

Published: August 9, 2026Updated: August 16, 2026

A noninvasive MRI examination creates images of the major arteries at the base of the brain to evaluate blood flow and identify narrowing or abnormal vessels.

Quick summary

["This MRA evaluates the brain's major arteries without injecting intravenous contrast."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
69161-8
Short code
MRA Circle of Willis WO+W contr IV
Synonyms
MRA Circle of Willis 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
mr-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?

This test is magnetic resonance angiography, or MRA, of the circle of Willis, a network of arteries at the base of the brain. It produces images of these blood vessels to assess their shape and the flow of blood through them.

Why might I need this test?

A circle of Willis MRA may be ordered to investigate symptoms that could be related to reduced cerebral blood flow, such as sudden weakness, difficulty speaking, vision changes, dizziness, or severe headache. It may also be used to evaluate known narrowing, a suspected aneurysm, or other vascular abnormalities.

How is the test performed?

You will lie on a table inside an MRI scanner while the machine creates images of the brain's arteries. The scan is noninvasive and, for the version without intravenous contrast, does not require contrast dye to be injected into a vein.

How do I prepare for the test?

Follow the instructions provided by the imaging center. Tell the care team if you have an implanted medical device, metal in your body, a history of claustrophobia, or any possibility of pregnancy. You may be asked to remove items such as jewelry, watches, and cards with magnetic strips.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Circle of Willis MRA without contrast

Frequently asked questions

Does this MRA use intravenous contrast?
The version represented by this test name is performed without intravenous contrast dye. The care team will confirm the exact protocol before the scan.
Is the procedure painful?
The scan itself is generally painless, although the MRI scanner can be noisy and may feel confined. Some people experience mild anxiety, and the care team can explain available comfort measures.
Why is the circle of Willis examined?
These arteries supply blood to important parts of the brain. Imaging this network can help identify narrowing, blockage, or abnormal blood-vessel formations that may be related to neurological symptoms.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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