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MR Angiography of the Circle of Willis with Intravenous Contrast

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

An MRI-based imaging test that evaluates blood vessels in the brain, particularly the circle of Willis, using intravenous contrast.

Quick summary

["This test creates detailed images of major brain arteries to help evaluate narrowing, blockage, or aneurysms."]

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

Key facts at a glance

LOINC
37254-0
Short code
MRA Circle of Willis W contr IV
Synonyms
MRA Circle of Willis 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?

MR angiography (MRA) of the circle of Willis is an MRI technique that produces detailed images of the major arteries at the base of the brain. Intravenous contrast may be used to make the blood vessels easier to see.

Why might I need this test?

This test may be ordered to investigate symptoms that could involve reduced blood flow to the brain, such as sudden or recurrent weakness, speech difficulty, or vision changes. It may also be used to evaluate known or suspected aneurysms, vessel narrowing, or vascular abnormalities.

How is the test performed?

You lie on a table that moves into an MRI scanner. The scanner takes multiple images while a radiologist reviews them; if contrast is used, it is given through a vein in your arm.

How do I prepare for the test?

Tell the imaging team about metal implants, claustrophobia, pregnancy, kidney problems, or any previous contrast reaction. Follow the facility's instructions, which may include avoiding food or drink for a limited time before the scan.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormal findings may include narrowing or blockage of a brain artery, an aneurysm, an abnormal vessel shape, or other blood-flow changes. These findings must be interpreted with symptoms, medical history, and other tests because some abnormalities can be incidental. A radiologist will explain the results and recommend follow-up if needed.

Short name

Circle of Willis MRA with contrast

Frequently asked questions

Does this test involve radiation?
No. MRI-based angiography does not use ionizing radiation, although the injected contrast may rarely cause an allergic-like reaction.
Is the contrast material the same as CT contrast?
Both can improve vessel images, but MRI contrast and CT contrast are different substances. Your care team can explain which is being used and what precautions apply.
How long does the test usually take?
The scan often takes about 30 to 60 minutes, although timing can vary with the facility, the specific protocol, and whether contrast is used.
  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