Magnetic Resonance Angiogram (MRA)

Test Overview

A magnetic resonance angiogram (MRA) is a type of magnetic resonance image (MRI) scan that uses a magnetic field and pulses of radio wave energy to provide pictures of blood vessels inside the body. In many cases, MRA can provide information that cannot be obtained from an X-ray, ultrasound, or computed tomography (CT) scan.

MRA can find problems with the blood vessels that may be causing reduced blood flow. With MRA, both the blood flow and the condition of the blood vessel walls can be seen. The test is often used to look at the blood vessels that go to the brain, kidneys, and legs. Information from an MRA can be saved and stored on a computer for further study. Photographs of selected views can also be made. See an illustration of an MRA.

During MRA, the area of the body being studied is placed inside an MRI machine. Contrast material is often used during MRA to make blood vessels show up more clearly.

Why It Is Done

A magnetic resonance angiogram (MRA) is done to look for:

• A bulge (aneurysm), clot, or the buildup of fat and calcium deposits (stenosis caused by plaque) in the blood vessels leading to the brain.
• Narrowing (stenosis) of the blood vessels leading to the lungs, kidneys, or legs.

How To Prepare

Before a magnetic resonance angiogram (MRA), tell your doctor and the MRI technologist if you:

• Are allergic to any medicines. The contrast material used for MRA does not contain iodine. If you know that you are allergic to the contrast material used for MRA, tell your doctor before having another test.
• Are or might be pregnant.
• Have a pacemaker, artificial limb, any metal pins or metal parts in your body (especially in your eyes), metal heart valves, metal clips in your brain, metal implants in your ear, tattooed eyeliner, or any other implanted or prosthetic medical device (such as a medicine infusion pump). Also, tell your doctor if you have worked around metal or if you have recently had surgery on a blood vessel. In some cases you may not be able to have the MRI test.
• Have an intrauterine device (IUD) in place. An IUD may prevent you from having the MRA test done.
• Become very nervous in small spaces. You need to lie very still inside the MRI machine, so you may need to have the test done with open MRI equipment. It is not as confining as standard MRI machines. You may need medicine to help you relax. Some blood vessels may not be seen clearly with an open MRI scanner.
• Have any other health conditions, such as kidney problems or sickle cell anemia, that may prevent you from having an MRA using contrast material.
• Wear any medication patches. The MRI may cause a burn at the patch site.

For some abdominal MRI tests, you may be asked to not eat or drink before the test.

You may need to arrange for someone to drive you home after the test, if you are given a medicine (sedative) to help you relax.

If you are having blood flow studies, do not use tobacco products, eat or drink (including alcohol or caffeinated beverages) for 2 hours before the test. Do not take iron supplements on the day of the test.

If you are breast-feeding and contrast material is used during the test, give your baby formula for 1 to 2 days after the procedure until the contrast material has passed from your body.

You may need to sign a consent form that says you understand the risks of an abdominal MRI and agree to have the test done. Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

A magnetic resonance angiogram (MRA) test is usually done by a magnetic resonance image (MRI) technologist. The resulting pictures are usually interpreted by a radiologist. However, some other types of doctors can also interpret an MRA scan.

Before the test

• Remove all metal objects, such as hearing aids, dentures, jewelry, watches, hairpins, wigs, and eyeglasses, from your body because these objects may be attracted to the powerful magnet used for the test. If you have had an car crash or an accident while working with metal, there is a possibility that you have metal fragments in your head, eyes, skin, or spine. An X-ray may be taken before the MRA to see if you can have the test.
• Take off all or most of your clothes, depending on which area is examined. You may be allowed to keep on your underwear if it does not get in the way. You will be given a cloth or paper covering to use during the test.
• Empty your pockets of any coins and cards, such as credit cards or ATM cards, with scanner strips on them, because the MRI magnet will erase the information encoded on the cards.

During the test

• You will lie on your back on a table that is part of the MRI scanner.
• Your head, chest, and arms may be held with straps to help you remain still.
• The table will slide into a space that contains the magnet. Depending on the part of your body to be examined, your head, limbs (such as your legs), or your entire body will be moved into the center of the magnet. Some MRI machines (open MRI) are now made so that the magnet does not surround the person being tested. Open MRI is less confining than a standard MRI but may not provide the same quality of image.
• Inside the scanner, you may hear a fan and feel air moving. You may also hear tapping or thumping noises as the MRA scans are taken. It is important to hold completely still while the scan is being done. Otherwise, repeat scans may be needed. You may be asked to hold your breath for short periods of time.
• You may be alone in the scanner room. However, the technologist will watch you through an observation window, and you will be able to talk to him or her through an intercom.

If contrast material is needed, the technologist will put it in an IV in your arm. The material may be given over 1 to 2 minutes. Then more MRI scans are done.

An MRA test usually takes 30 to 90 minutes but can take as long as 2 hours.

How It Feels

You won't have pain from the magnetic field or radio waves used for the MRI test. The table you lie on may feel hard and the room may be cool. You may be tired or sore from lying in one position for a long time.

Some people feel discomfort or anxiety (claustrophobia) inside the MRI magnet. If this keeps you from lying still, you can be given a sedative to help you relax. Open MRI machines are less confining than standard MRI and may be helpful if you are claustrophobic.

If a contrast material is used, you may feel some coolness and flushing as it is put into your IV. In rare cases, you may feel:

• A tingling feeling in the mouth if you have metal dental fillings.
• Warmth in the area being examined. This is normal. Tell the technologist if you have nausea, vomiting, headache, dizziness, pain, burning, or breathing problems.

Risks

There is a slight risk of having an allergic reaction if contrast material is used during the MRA scan. Most reactions can be controlled using medicine.

Results

A magnetic resonance angiogram (MRA) is a type of magnetic resonance image (MRI) scan that uses a magnetic field and pulses of radio wave energy to provide pictures of blood vessels inside the body. The radiologist may talk to you about the results of your MRA right after the test. Complete results are usually available for your doctor in 1 to 2 days.

Conventional angiogram or computerized tomography angiogram (CT angiogram) may be needed after MRA if a problem, such as an aneurysm, is found or if surgery may be needed.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Pregnancy. Although the strong magnetic field used for an MRA does not appear to be harmful, MRA usually is not done when you are pregnant. If a view of your belly is needed and you are pregnant, an ultrasound test may be done instead.
• You are using a medical device that contains metal, such as an IUD, a pacemaker, some types of artificial limbs, or medicine infusion pumps. These devices can malfunction or cause problems during an MRA scan.
• Not being able to lie still during the test. The results of MRA may not be accurate if you cannot remain still during the test.
• Being overweight and not fitting into the opening of some MRI scanners.

What To Think About

• While MRA is a safe and valuable test for looking at blood vessels inside the body, it is more expensive than other imaging techniques, and it may not be available in all medical centers.
• An advantage of MRA is that no radiation is involved.
• Open MRI machines are now made so that the magnet does not completely surround you. Open MRI is useful for people who are claustrophobic or obese. However, these machines are not available everywhere. Also, these machines may not be able to do all the studies needed to check for problems.
• Conventional angiogram or computerized tomography angiogram (CT angiogram) may be done to double check abnormal results found during MRA, especially if surgery is being considered to treat the problem.
• MRA results may indicate an aneurysm is present when it is not (false-positive). It may also show no aneurysm when one is present (false-negative). MRA is most accurate for larger blood vessels.
• You may need to wait for 6 weeks before having an MRA if you have had a stent put in your coronary arteries. This helps decrease the chances of movement of the stent by the magnet used in the MRA.