Magnetic resonance imaging (MRI) of the breast — or breast MRI — is a test used to detect breast cancer and other abnormalities in the breast.
A breast MRI captures multiple images of your breast. Breast MRI images are combined, using a computer, to generate detailed pictures.
A breast MRI usually is performed after you have a biopsy that's positive for cancer and your doctor needs more information about the extent of the disease. In certain situations, such as for women with a high risk of breast cancer, have a very strong family history of breast cancer or carry a hereditary breast cancer gene mutation, a breast MRI may be used with mammograms as a screening tool for detecting breast cancer.
Why it's done
A breast MRI is most often used to screen for breast cancer in women thought to have a high risk of the disease. A breast MRI may also be used to assess the extent of breast cancer.
Your doctor may recommend a breast MRI if:
- You've been diagnosed with breast cancer and your doctor wants to determine the extent of the cancer
- You have a suspected leak or rupture of a breast implant
- You're at high risk of breast cancer, defined as a lifetime risk of 20 percent or greater, as calculated by risk tools that take your family history and other factors into consideration
- You have a strong family history of breast cancer or ovarian cancer
- You have very dense breast tissue, and mammograms didn't detect a prior breast cancer
- You have a history of precancerous breast changes — such as atypical hyperplasia or lobular carcinoma in situ — and a strong family history of breast cancer and dense breast tissue
- You have a hereditary breast cancer gene mutation (e.g., BRCA1 or BRCA2)
- You have had radiation treatments to your chest area before age 30
If you're unsure whether you're considered high risk, ask your doctor to help you determine your personal risk estimate. A referral to a breast clinic or breast health specialist may help you better understand your risk and your screening options.
A breast MRI is intended to be used in addition to a mammogram or another breast-imaging test — not as a replacement for a mammogram. Although it's a sensitive test, a breast MRI can still miss some breast cancers that a mammogram will detect.
A breast MRI is a safe procedure that doesn't expose you to radiation. But as with other tests, a breast MRI has risks, such as:
- A risk of false-positive results. A breast MRI may identify suspicious areas that, after further evaluation — such as a breast ultrasound or breast biopsy — turn out to be benign. These results are known as "false-positives." A false-positive result may cause unneeded anxiety if you undergo additional testing, such as a biopsy, to assess the suspicious areas.
- A risk of reaction to the contrast dye used. A breast MRI involves injection of a dye to make the images easier to interpret. This dye can cause allergic reactions and can cause serious complications for people with kidney problems.
How you prepare
To prepare for a breast MRI, your doctor may recommend that you:
- Schedule your MRI for the beginning of your menstrual cycle. If you're premenopausal, the MRI facility may prefer to schedule your MRI at a certain point during your menstrual cycle, around days 7 to 14. The first day of your menstrual bleeding is day one of your cycle. Let the facility know where you are in your cycle so that optimal timing for the breast MRI can be arranged.
- Tell your doctor about any allergies you have. Most MRI procedures use a dye to make the images easier to interpret. The dye is usually given through a vein in your arm. Tell your doctor about any allergies to avoid complications with the dye.
- Tell your doctor if you have kidney problems. A dye commonly used to enhance MRI images called gadolinium can cause serious complications in people with kidney problems. Tell your doctor if you have a history of kidney problems.
- Tell your doctor if you're pregnant. An MRI generally isn't recommended for women who are pregnant.
- Tell your doctor if you're nursing. If you're nursing, your doctor may recommend that you stop for two days after your MRI. The American College of Radiology states that the risk to your baby from the contrast dye is extremely low. However, if you're concerned, stop breast-feeding for 12 to 24 hours after the MRI, which will give your body time to eliminate the contrast dye. You may pump and discard your milk during this period. You can pump and store milk before the procedure to feed your baby.
- Don't wear anything metallic during the MRI. Metallic objects, such as necklaces, hairpins and watches, can be damaged during an MRI. Leave metallic objects at home or remove them before your MRI.
- Tell your doctor about implanted medical devices. If you have an implanted medical device, such as a pacemaker, defibrillator, implanted drug port or artificial joint, tell your doctor before your MRI.
What you can expect
When you arrive for your appointment, a member of your health care team will give you a gown and a robe to wear. You'll receive instructions on removing clothing and jewelry. If you have trouble being in a small, confined space, tell your doctor before your breast MRI. You may be given a mild sedative.
A dye (contrast agent) may be injected through an intravenous (IV) line in your arm to enhance the appearance of tissues or blood vessels on the MRI pictures.
The MRI machine has a large, central opening. During the breast MRI, you lie facedown on a padded scanning table. Your breasts fit into a hollow depression in the table, which contains coils that detect magnetic signals from the MRI machine. The entire table then slides into the opening of the machine.
The MRI machine creates a magnetic field around you, and radio waves are directed at your body. You won't feel the magnetic field or radio waves, but you may hear loud tapping and thumping sounds coming from inside the machine. Because of this, you may be given earplugs to wear.
During the test, the technologist monitors you from another room. You can speak to the technologist through a microphone. You'll be instructed to breathe normally but to lie as still as possible.
The breast MRI appointment may take 30 minutes to one hour.
A doctor specializing in imaging techniques (radiologist) reviews the images from your breast MRI, and a member of your health care team will contact you to discuss the results of the test.