Test Overview

Magnetic resonance imaging (MRI) uses a magnetic field and pulses of radio waves to make pictures of the breast. MRI may show problems in the breast that cannot be seen on an X-ray, ultrasound, or CT scan.

The MRI records pictures that show your breast's normal structure; tissue damage or disease, such as infection; inflammation; or a lump. MRI is better than mammography or ultrasound for looking at some breast lumps.

In most cases, a dye (contrast material) may be used so that abnormalities can be seen more clearly from normal breast tissue. The contrast material makes it easier to find problems with increased or abnormal blood flow, such as with some types of cancer or areas of inflammation.

MRI is a safe and valuable test for looking at the breast, but it has a high rate of false-positive results, and it is more costly than other methods and is not available in all hospitals.

See pictures of a standard MRI machine and an open MRI machine.

Why It Is Done

An MRI of the breast is done to:

• Find breast cancer. Most often, an MRI is used to check breast lumps found during a physical examination, ultrasound, or mammography.
• Check high-risk women. MRI may be recommended as a screening tool for very high-risk women, such as those who test positive for the BRCA1 or BRCA2 gene, or who have two or more close family members who have had breast or ovarian cancer before age 50.
• Check women who have dense breast tissue.
• Check the opposite breast. MRI is sometimes used to evaluate the opposite breast in women diagnosed with certain types of breast cancer.
• See what stage of breast cancer is present so the best treatment can be chosen.
• Look at breast tissue changes during treatment for breast cancer.
• Check breasts with inverted nipples for any sign of breast cancer.
• Find a breast implant rupture. MRI of the breast is the best test for this purpose.
• Look at a suspicious area of the breast for women with breast implants.

How To Prepare

Tell your doctor and the MRI technologist if you:

• Have a pacemaker, implantable cardioverter-defibrillator (ICD), artificial limb, any metal parts in your body, tattooed eyeliner or metallic-based tattoos, or any other implanted medical device, such as a medication 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.
• Are or might be pregnant.
• Become very nervous in confined spaces. You need to lie very still inside the MRI scanner, so you may need to have the test done with an open MRI machine that is not as confining as standard MRI machines, or you may need medicine to help you relax.
• Have allergies, especially to any medicines.
• Have asthma.
• Have other health problems, such as kidney problems or sickle cell anemia. Contrast material cannot be used with some health problems.

Arrange to have someone take you home after the test in case you are given a medicine (sedative) to help you relax.

You may need to sign a consent form that says you understand the risks of an MRI and agree to have the test done. Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. 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

An MRI of the breast is usually done by an MRI technologist. A radiologist usually studies the pictures to look for problems. But some other types of doctors may also do this.

Before the test

You will need to remove all metal objects (such as hearing aids, dentures, jewelry, watches, and hairpins) from your body because these objects may be attracted to the powerful magnet used for the test. If there is a possibility that you have metal fragments in your eyes from an accident or a surgery or because you work around metal, an X-ray or a CT scan will be done before the MRI to see if any metal is present. An X-ray or CT may also be done if there is a concern about metal fragments in your head or spine.

You will need to take off your clothes above the waist. You will be given a gown to cover your shoulders 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 may erase the information on the cards.

During the test

During the test, you will lie on your back on a table that is part of the MRI scanner. Some machines have specially designed tables on which you lie on your stomach. Straps may be used to help keep your body in the best position. The table will slide into the machine part that holds the magnet. A device called a coil may be placed over or wrapped around the breast area. Some MRI machines (called open MRI) are now made so that the scanner does not enclose your whole body.

Inside the scanner, you will hear a fan and feel air moving. You may also hear tapping or thumping noises as the MRI scans are taken. You may be given earplugs or headphones with music to lessen the noise. It is very important to hold completely still while the scan is being done. Otherwise, repeat scans may be needed. Also, you may be asked to hold your breath for short periods of time.

During the test, you may be alone in the scanner room. But the technologist will watch you through a window, and you will be able to talk to him or her through a speaker.

If contrast material is needed, the technologist will put it in a vein (intravenous, or IV) in your arm. The contrast material may be given over 1 to 2 minutes. Then more MRI scans are taken.

An MRI test usually takes 30 to 60 minutes but may last as long as 2 hours.

How It Feels

You will not have pain from the magnetic field or radio waves. The table you lie on may feel hard and the room may be cool. You may become uncomfortable from lying in one position for a long time.

Some people feel anxious (claustrophobic) inside the MRI machine. You may be given medicine (sedative) to help you relax. Open MRI machines are less confining than a standard MRI and may be helpful if you are claustrophobic.

If dye is used, you may feel some coolness and flushing as it is put into your vein.

In rare cases, you may feel:

• A tingling sensation in your mouth if you have metal dental fillings.
• Warmth in the breast. This is normal and does not need treatment unless it becomes bothersome. Tell the technologist if you:
  • Have any breathing problems.
  • Feel sick to your stomach.
  • Have a headache.
  • Feel dizzy.
  • Have pain.
  • Feel a burning sensation.
  • Have itchy skin.

Risks

There are no known harmful effects from the strong magnetic field used for MRI. But the magnet is very powerful. The magnet may affect pacemakers, implantable cardioverter-defibrillators (ICDs), artificial limbs, and other medical devices that contain iron.

If you may have metal fragments in your eyes, an MRI can cause damage to the retina. If there is a concern about metal fragments in the eye, most MRI clinics will do X-rays of the eyes before the MRI. If metal is found on the X-ray, the MRI will not be done.

Iron pigments in tattoos or tattooed eyeliner can cause skin or eye irritation problems.

There is a small risk of having an allergic reaction if contrast material is used during the MRI scan. Most reactions are mild and can be treated with medicine. There is also a small risk of infection at the IV site.

Results

Magnetic resonance imaging (MRI) uses a magnetic field and pulses of radio waves to make pictures of the breast.

The radiologist may discuss the results of the MRI with you right after the test. Complete results are usually available to your doctor in 1 to 2 days.

An MRI scan can sometimes find a problem in a breast, even when the size and shape of the breast looks normal.

What Affects the Test

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

• Pregnancy. An MRI test usually is not done during pregnancy. If you are pregnant, an ultrasound test may be done instead.
• Medical devices that have metal, such as a pacemaker or an ICD. These devices may not function properly or can cause problems during an MRI scan.
• Other types of metal, such as surgical clips. If these will interfere with a breast MRI, the test will not be done.
• The inability to remain still during the test.
• Being very overweight. This may affect your ability to fit into the opening of some standard MRI machines.

What To Think About

• Abnormal findings on a breast MRI often are not cancer. If the MRI has an abnormal result, your doctor will do other testing to find out if the problem is serious. This may involve doing an ultrasound test or a biopsy, or both.
• Sometimes your MRI test results may be different because you were tested at a different medical center or earlier test results are not available to compare to the new test findings.
• An MRI may be more likely to report a problem in the breast when a problem is not there (false-positive) than other tests. A false-positive result may lead to more tests when no serious problem is present. For more information, see the medical test Breast Cancer (BRCA) Gene Test.
• While MRI is a safe and valuable test for looking at your breast, it is much more costly than other methods, and it may not be available in your area.
• 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. But these machines are not available everywhere. Also, these machines may not be able to do all the studies needed to check for problems. Open MRI can be used to guide treatments (interventional treatments) or procedures, such as a biopsy.
• Contrast material that contains gadolinium may cause a serious problem (called nephrogenic systemic fibrosis) in people with kidney failure. Tell your doctor if you have serious kidney disease before having an MRI scan.

References

Other Works Consulted

• Lehman CD, et al. (2007). MRI evaluation of the contralateral breast in women with recently diagnosed breast cancer. New England Journal of Medicine, 356(13): 1295–1303.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.

• Saslow D, et al. (2007). American Cancer Society guidelines for breast screening with MRI as an adjunct to mammography. CA: A Cancer Journal for Clinicians, 57(2): 75–89. Available online: http://www.caonline.amcancersoc.org/cgi/content/full/57/2/75.

• Silverstein MJ, et al. (2005). Image-detected breast cancer: State of the art diagnosis and treatment. Journal of the American College of Surgeons, 201(4): 586–597.

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