Breast MRI scan

Definition

A breast MRI (magnetic resonance imaging) scan is an imaging test that uses powerful magnets and radio waves to create pictures of the breast and surrounding tissue. It does not use radiation (x-rays).

A breast MRI may be done in combination with mammography or ultrasound. But it is not a replacement for mammography. 

Alternative Names

MRI - breast; Magnetic resonance imaging - breast

How the test is performed

You lie on your stomach with your breasts hanging down into cushioned openings. The narrow table slides into the MRI scanner, which is shaped like a tunnel.

You may be asked to wear a hospital gown or clothing without metal fasteners (such as sweatpants and a T-shirt). Certain types of metal can cause blurry images.

Some exams require a special dye (contrast). The dye is usually given before the test through a vein (IV) in your hand or forearm. The dye helps the radiologist see certain areas more clearly.

During the MRI, the person who operates the machine watches you from another room. The test most often lasts 30 to 60 minutes. It may take longer.

How to prepare for the test

You may be asked not to eat or drink anything for 4 to 6 hours before the scan.

Tell your doctor if you are afraid of close spaces (have claustrophobia). You may be given a medicine to help you relax and feel less anxious. Or your doctor may suggest an open MRI, in which the machine is not as close to the body.

Before the test, tell your health care provider if you have:

  • Brain aneurysm clips
  • Certain types of artificial heart valves
  • Heart defibrillator or pacemaker
  • Inner ear (cochlear) implants
  • Kidney disease or dialysis (you may not be able to receive the IV contrast)
  • Recently placed artificial joints
  • Certain types of vascular stents
  • Worked with sheet metal in the past (you may need tests to check for metal pieces in your eyes)

Because the MRI contains strong magnets, metal objects are not allowed into the room with the MRI scanner:

  • Pens, pocketknives, and eyeglasses may fly across the room.
  • Items such as jewelry, watches, credit cards, and hearing aids can be damaged.
  • Pins, hairpins, metal zippers, and similar metallic items can distort the images.
  • Removable dental work should be taken out just before the scan.

How the test will feel

An MRI exam causes no pain. If you have difficulty lying still or are very nervous, you may receive medicine to relax you. Too much movement can blur MRI images and cause errors.

The table may be hard or cold. You can ask for a blanket or pillow to stay comfortable. The machine produces loud thumping and humming noises when turned on. You will likely be given ear plugs to help reduce the noise.

An intercom in the room allows you to speak to someone at any time. Some MRIs have televisions and special headphones that you can use to pass the time.

There is no recovery time, unless you were given a medicine to relax. After an MRI scan, you can resume your normal diet, activity, and medications.

Why the test is performed

MRI provides detailed pictures of the breast. It also provides clear pictures of parts of the breast that are difficult to see clearly on an ultrasound or mammogram.

Breast MRI may also be performed to:

  • Check for more cancer in the same breast or the other breast after breast cancer has been diagnosed
  • Distinguish between scar tissue and tumors in the breast
  • Evaluate a breast lump (usually after biopsy)
  • Evaluate an abnormal result on a mammogram or breast ultrasound
  • Evaluate for possible rupture of breast implants
  • Find any cancer that remains after surgery or chemotherapy
  • Guide a biopsy (rare)
  • Screen for cancer in women at very high risk for breast cancer (such as those with a strong family history)
  • Screen for cancer in women with very dense breast tissue

An MRI of the breast can also show:

  • Blood flow through the breast area
  • Blood vessels in the breast area

What abnormal results mean

Abnormal results may be due to:

Consult your health care provider with any questions and concerns.

What the risks are

MRI contains no radiation. To date, no side effects from the magnetic fields and radio waves have been reported.

The most common type of contrast (dye) used is gadolinium. It is very safe. Allergic reactions to the substance rarely occur. Gadolinium can be harmful to patients with kidney problems who require dialysis. If you have kidney problems, tell your health care provider before the test.

The strong magnetic fields created during an MRI can make heart pacemakers and other implants not work as well. It can also cause a piece of metal inside your body to move or shift.

Special considerations

Breast MRI is more sensitive than mammogram, especially when it is performed using contrast dye. However, breast MRI may not always be able to distinguish breast cancer from noncancerous breast growths. This can lead to a false positive result.

MRI also cannot pick up tiny pieces of calcium (microcalcifications), which mammogram can detect.

A biopsy is needed to confirm the results of a breast MRI.

References

Lehman CD, DeMartini W, Anderson BO, Edge SB. Indications for breast MRI in the patient with newly diagnosed breast cancer. JNCCN. 2009;7:193-201.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Breast cancer. Version 1.2013. Available at http://www.nccn.org/professionals/physician_gls/pdf/breast.pdf. Accessed November 16, 2012.

Saslow D, Boetes C, Burke W, et al. American Cancer Society guidelines for breast screening with MRI as an adjunct to mammography. CA Cancer J Clin. 2007;57:75-89.

Tartar M, Comstock CE, Kipper MS. Breast Cancer Imaging: A Multidisciplinary, Multimodality Approach. Philadelphia, PA: Elsevier Mosby; 2008:chap 2.

Revision

Last reviewed 3/4/2013 by Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Blackman, Stephanie Slon, and Nissi Wang.

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