Test Overview

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 can't 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's not available in all hospitals.

An abbreviated breast MRI is a newer test that takes less time than a standard MRI. (You might hear it called a "fast MRI.") This test is something your doctor or breast cancer screening centre may offer.

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

In general, there's nothing you have to do before this test, unless your doctor tells you to.

Tell your doctor if you get nervous in tight spaces. You may get a medicine to help you relax. If you think you'll get this medicine, be sure you have someone to take you home.

How It Is Done

Before the test

You will need to remove all metal objects (such as hearing aids, dentures, jewellery, watches, and hairpins) from your body. These objects may be attracted to the powerful magnet used for the test.

You will need to 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's not in the way.) You will be given a gown to use during the test. If you are allowed to keep some of your clothes on, make sure your pockets are empty.

If you wear a medicine patch, you may need to remove it. The MRI can cause burns with some patches.

During the test

During the test, you will lie 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.

Some people feel nervous inside the MRI magnet. If this keeps you from lying still, you can be given a medicine (sedative) to help you relax.

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. 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'll be able to talk back and forth.

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.

How long the test takes

The test usually takes 30 to 60 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. But you may be tired or sore from lying in one position for a long time.

If a contrast material is used, you may feel some coolness when it is put into your IV.

In rare cases, you may feel:

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

Risks

There are no known harmful effects from the strong magnetic field used for an MRI. But the magnet is very powerful. It may affect any metal implants or other medical devices you have.

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.

Risks from contrast material

Contrast material that contains gadolinium may be used in this test. But for most people, the benefit of its use in this test outweighs the risk. Be sure to tell your doctor if you have kidney problems or are pregnant.

There is a slight chance of an allergic reaction if contrast material is used during the test. But most reactions are mild and can be treated using medicine.

If you breastfeed and are concerned about whether the contrast material 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 are concerned, you can stop breastfeeding for up to 24 hours after the test. During this time, you can give your baby breast milk that you stored before the test. Don't use the breast milk you pump in the 24 hours after the test. Throw it out.

Results

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.