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MRI (Magnetic Resonance Imaging)

Reviewed by: Emily F. Conant, MD

Updated October 1, 2010

Magnetic resonance imaging, commonly known as MRI, uses magnets and radio waves to create cross-sectional images of areas of the body. Doctors may use it to check for breast abnormalities in women at high risk for developing breast cancer, or to better map the size of a cancer in a recently diagnosed woman before she has surgery or therapy. MRIs may also be used to monitor how a breast cancer responds to therapy after starting treatment for early-stage or metastatic breast cancer.

Outside of large cities, it may be difficult to find MRI centers with machines built especially for taking pictures of the breast. Make sure your center has one.

Getting the Test

Before the test, you will get an IV (intravenous injection into the vein) with a contrast solution, which will help highlight any areas of abnormality. The contrast material flows in the blood and is attracted to areas with the high blood flow that often exists around tumors.

You should remove metal jewelry, glasses or other objects. Let the radiologist know if you have metal in your body, such as a pacemaker, which the MRI machine could move. You may be asked to change into a hospital gown, and you will need to remove most of your clothes for this test.

During the MRI test, you will lie on your stomach on a soft table with padded openings for your breasts. The table will be slid inside the MRI machine, which usually looks like rounded tube with openings at both ends. If you are afraid of narrow or enclosed spaces, find out if an open MRI machine is available, or ask your doctor to give you a mild sedative.

While you are in the machine, you will hear noises that sound like thumping or tapping. Some people find that wearing ear plugs helps block out the noise. The technologist doing your study should provide ear plugs for you if you ask for them. You should not feel any pain during the test, but you may be uncomfortable from lying on the table. The test should last about 30-45 minutes, and you will need to lie very still.

Benefits and Challenges

MRI takes more detailed pictures than mammogram in young women, who tend to have very dense breasts. And because of the IV contrast used, MRI can find some cancers that cannot be seen with mammography. The test is recommended if you have a breast cancer gene mutation, you have a strong family history of breast cancer, you’ve had radiation to your chest between the ages of 10 and 30 or if you have some other very specific genetic diseases.

If your doctor already found a breast abnormality, MRI can look more closely at it. MRI helps doctors to learn more about lumps that can be felt but a mammogram does not see, find cancer in the breast after it has been found in the lymph nodes, detect the spread of cancer throughout the breast or look at silicone breast implants.

MRI is not for everyone. It is much more expensive than mammography and ultrasound. Though it often shows more detailed pictures than other breast imaging studies, MRI can highlight areas of the breast that are not cancer and cause “false positive” test results and unneeded biopsies. Also, MRI can miss some cancers, so it is often recommended in combination with mammogram and ultrasound.