Magnetic resonance imaging (MRI) uses a magnetic field and pulses of radio waves to make pictures of the breast. It does not use X-rays. MRI may show problems in the breast that cannot be seen on a mammogram, ultrasound, or CT scan.
The MRI makes 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.
You may be able to have an MRI with an open machine that doesn't enclose your entire body. But open MRI machines aren't available everywhere. The pictures from an open MRI may not be as good as those from a standard MRI machine.
Why It Is Done
An MRI of the breast is done to:
- Find breast cancer. Breast MRI may be done when a mammogram or breast ultrasound scan cannot tell if a lump is cancer.
- Check women who are at increased risk for breast cancer. This includes women with:
- Gene changes (such as BRCA).
- Close family members who have had breast cancer.
- A history of radiation therapy to the chest as a child.
- Choose the best treatment for breast cancer. It may also be used to check breast tissue changes during treatment.
- Check breasts with nipple changes for signs of breast cancer. These changes include inverted nipples, nipples with scaly skin that flakes off, and nipples with abnormal discharge.
- Check women with breast implants. MRI may be used to look for breast cancer or to check if the implant is leaking.
Women at increased risk for breast cancer may have screening tests that alternate between MRIs and mammograms. This is done because the tests can detect different kinds of problems.
How To Prepare
Before your MRI test, tell your doctor and the MRI technologist if you:
- Are allergic to any medicines. The contrast material used for MRI does not contain iodine. If you know that you are allergic to the contrast material used for the MRI, tell your doctor before having another test.
- Are or might be pregnant.
- Have any metal implanted in your body. This helps your doctor know if the test is safe for you. Tell your doctor if you have:
- Heart and blood vessel devices, such as a coronary artery stent, a pacemaker, an ICD (implantable cardioverter-defibrillator), or a metal heart valve.
- Metal pins, clips, or metal parts in your body, including artificial limbs and dental work or braces.
- Any other implanted medical device, such as a medicine infusion pump or a cochlear implant.
- Cosmetic metal implants, such as in your ears, or tattooed eyeliner.
- Had recent 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 MRI test done.
- Become very nervous in confined spaces. You need to lie very still inside the MRI magnet, so you may need medicine to help you relax.
- Have any other health conditions, such as kidney problems or sickle cell anemia, that may prevent you from having an MRI using contrast material.
- Are taking medicines or wearing a medicine patch. You may need to stop taking certain medicines for a time before, during, or after the MRI. And if you're wearing a medicine patch, the MRI may cause a burn at the patch site.
Arrange to have someone take you home after the test in case you are given a medicine (sedative) to help you relax.
You may be asked to sign a consent form that says you understand the risks of the test and agree to have it 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, jewellery, 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 stomach on a table that is part of the MRI scanner. 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.
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.
If dye is used, you may feel some coolness when 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.
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.
Metal parts in the eyes can damage the retina. If you may have metal fragments in the eye, an X-ray of the eyes may be done before the MRI. If metal is found, the MRI will not be done.
Iron pigments in tattoos or tattooed eyeliner can cause skin or eye irritation.
An MRI can cause a burn with some medicine patches. Be sure to tell your health professional if you are wearing a patch.
There is a slight risk of an allergic reaction if contrast material is used during the MRI. But most reactions are mild and can be treated using medicine. There also is a slight risk of an infection at the IV site.
A dye (contrast material) that contains gadolinium may be used in this test. Be sure to tell your doctor if:
- You are pregnant or think you may be pregnant.
- You have kidney problems.
- You've had more than one test that used gadolinium.
Health Canada has safety warnings about gadolinium. But for most people, the benefit of its use in this test outweighs the risk.
If you breastfeed and are concerned about whether the dye used in this test is safe, talk to your doctor. Most experts believe that very little dye passes into breast milk and even less is passed on to the baby. But if you prefer, you can store some of your breast milk ahead of time and use it for a day or two after the test.
An MRI may be more likely than other tests to report a problem in the breast when a problem is not there (false-positive). A false-positive result may lead to more tests such as a biopsy when no serious problem is really present. So MRI is not used as a screening test for women at low or average risk for breast cancer.
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 less than 14 days.
An MRI scan can sometimes find a problem in a breast, even when the size and shape of the breast looks normal.
The breast tissue looks normal in size, shape, and appearance.
No solid masses are present.
A breast implant is intact.
No signs of inflammation or infection are present.
Solid masses are present.
Signs of infection or inflammation are present.
A breast implant is ruptured.
Underarm lymph nodes do not look normal.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- 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.
- 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 centre or earlier test results are not available to compare to the new test findings.
- 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.
Other Works Consulted
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Kuhl C (2007). The current status of breast MR imaging, part 2: Clinical applications. Radiology, 244(3): 672–691.
- Kuhl C (2007). The current status of breast MR imaging, part I. Choice of technique, image interpretation, diagnostic accuracy, and transfer to clinical practice. Radiology, 244(2): 356–378.
- Morrow M, et al. (2011). MRI for breast cancer screening, diagnosis, and treatment. Lancet 378(9805): 1804–1811.
- Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
Adaptation Date: 2/7/2019
Adapted By: HealthLink BC
Adaptation Reviewed By: HealthLink BC
Adaptation Date: 2/7/2019
Adapted By: HealthLink BC
Adaptation Reviewed By: HealthLink BC