The short answer: An MR angiogram (MRA) is an MRI exam of your blood vessels. It uses a magnetic field and radio waves, not X-rays, and no tube goes into an artery. Doctors order it to look for narrowed, blocked, bulging, or torn vessels in the brain, neck, chest, abdomen, or legs. Some MRA scans need a gadolinium contrast injection, and some do not.
What is an MR angiogram?
MedlinePlus defines magnetic resonance angiography as an MRI exam of the blood vessels. A standard MRI shows organs and soft tissue. An MRA is set up to make flowing blood stand out, so the vessel shows as a bright channel.
The older test, catheter angiography, puts a thin tube into an artery and injects dye under X-ray. MRA is noninvasive. The Radiological Society of North America and the American College of Radiology state on RadiologyInfo.org that MRA does not use radiation and may require an injection of contrast material.
The scanner is the same machine used for any MRI. If you have not had one, read what to expect at your first MRI.
Why would a doctor order an MRA?
An MRA answers a question about a vessel, not about an organ. RadiologyInfo.org lists exams of vessels in the brain, neck, heart, chest, abdomen, pelvis, legs, and arms. MedlinePlus and RadiologyInfo.org name these common reasons:
- Aneurysm: a bulge in an artery wall.
- Carotid artery disease: plaque in the neck arteries that supply the brain.
- Stroke workup: a search for a blocked or narrowed vessel.
- Aortic dissection or coarctation: a tear in the aorta, or a narrow segment of it.
- Renal artery stenosis: narrowing of an artery that feeds a kidney.
- Narrowed leg arteries: part of a workup for peripheral artery disease.
- Mesenteric artery ischemia: poor blood flow to the intestines.
- Arteriovenous malformations and vessel problems present from birth.
Surgeons also use MRA to plan a procedure, for example to map the vessels around a tumor before an operation.
Does an MRA need contrast dye?
It depends on the vessel and the question. There are two approaches.
Contrast-enhanced MRA. A technologist injects a gadolinium-based agent into a vein in your hand or arm. The scanner takes pictures as the agent passes through the arteries. One FDA label, for gadobutrol (Gadavist), lists MRA to evaluate known or suspected supra-aortic or renal artery disease among its approved uses. Our guide to MRI with contrast explains how gadolinium works.
Non-contrast MRA. The scanner uses the movement of blood itself to make the picture. A 2023 review in Magnetic Resonance Imaging Clinics of North America calls these methods an attractive alternative to contrast-enhanced MRA and a radiation-free alternative to CT angiography. A 2019 review in Circulation: Cardiovascular Imaging reports renewed interest in noncontrast MRA for leg arteries. The authors give two reasons: many people with peripheral artery disease also have chronic kidney disease, and gadolinium can stay in the body.
Kidney function matters most for the contrast decision. The gadobutrol label carries a boxed warning for nephrogenic systemic fibrosis (NSF), a serious scarring disease of the skin and organs. The label says the risk appears highest with chronic, severe kidney disease (GFR below 30 mL/min/1.73m2) or acute kidney injury. RadiologyInfo.org describes NSF as exceptionally rare with newer gadolinium agents.
The same label advises a kidney blood test for people at risk of reduced kidney function. Its examples are age over 60, diabetes, and chronic hypertension. If you manage high blood pressure, hypertension.md covers that condition in plain language.
How does MRA compare with CT angiography and catheter angiography?
All three tests show blood vessels. They differ in radiation, contrast type, and invasiveness.
- MRA: no radiation. Contrast, when used, is gadolinium. RadiologyInfo.org states that gadolinium is less likely to cause an allergic reaction than the iodinated contrast used for CT angiography.
- CT angiography: uses X-rays and an iodine-based dye. The NHLBI notes that cardiac CT carries a very slight risk of cancer from radiation, and that the dye can damage the kidneys in rare cases. CT shows calcium in vessel walls. MRA does not.
- Catheter angiography: a tube goes into an artery, and iodine dye is injected under X-ray. For the coronary form of this test, the NHLBI lists risks that include bleeding, infection, blood vessel damage, and kidney problems. Its images of small vessels can be clearer than MRA images.
RadiologyInfo.org adds that MRA may take less time than catheter angiography, costs less, and needs no recovery period unless you had sedation. For a wider comparison of the two scanners, see MRI against CT.
What is an MRA scan like?
The exam feels like any other MRI. The steps below come from MedlinePlus and RadiologyInfo.org.
- Before the scan. You may be asked not to eat or drink for 4 to 6 hours. Take your regular medicines unless your doctor says otherwise. Tell the team about any pacemaker, aneurysm clip, cochlear implant, insulin pump, stent, or kidney disease.
- Setup. You change into a gown or metal-free clothes. If contrast is planned, a small IV goes into your hand or arm.
- The scan. You lie on your back on a narrow table that slides into the tunnel. The machine is loud, and you get ear protection. Some sequences need a breath hold of 15 to 25 seconds.
- After the scan. MedlinePlus states that the exam causes no pain and has no recovery time, unless you had a medicine to relax.
MedlinePlus says the test may take 1 hour or more. The time depends on the body area and on whether contrast is used.
What are the limits of an MRA?
An MRA is not the right test for every vessel question. RadiologyInfo.org lists these limits:
- It cannot show calcium deposits in vessel walls.
- Small arteries can look less clear than on catheter angiography.
- Arteries and veins can be hard to separate in the images.
- Movement, breathing, and an irregular heartbeat can blur the pictures.
- Implants and metal can distort the image or rule out the scan.
- Some scanners have weight limits.
A clear result does not always end the workup. The gadobutrol label warns that the sensitivity of its MRA for significant narrowing (over 50% in renal arteries, over 70% in supra-aortic arteries) has not been shown to exceed 55%. The label states that a negative MRA alone should not be used to rule out significant stenosis. Your doctor reads the result with your symptoms and other tests.
Contrast has its own cautions. The label states that gadolinium is retained for months or years in several organs. Linear agents cause more retention than macrocyclic agents. The consequences of retention in the brain have not been established. In pregnancy, the label says to use the agent only if imaging is essential and cannot be delayed.
The bottom line
An MRA is an MRI that maps your blood vessels without radiation and without a catheter. Doctors order it for suspected aneurysms, narrowed carotid, renal, or leg arteries, and problems of the aorta. Many MRA scans work without contrast. That matters if your kidneys are weak. The test cannot show calcium, and it can miss some narrowing, so a doctor may add CT angiography or catheter angiography. Ask your doctor which vessel is in question and whether your scan needs contrast.
Last updated: October 2026. This article is for informational purposes only and does not constitute medical advice. Talk with your doctor or radiologist about which blood vessel imaging test fits your situation.