Breast MRI: Imaging test to detect breast cancer

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Breast MRI: Imaging test to detect breast cancer

Breast MRI — Learn who it's for, how it's done and what the risks are.

Magnetic resonance imaging (MRI) of the breast — or breast MRI — is a breast-imaging technique that captures multiple cross-sectional pictures of your breast and combines them, using a computer, to generate detailed, 2-D and 3-D pictures. Breast MRI is performed when doctors need more information than a mammogram, ultrasound or clinical breast exam can provide.

Who is breast MRI for?

Breast MRI isn't used routinely for breast cancer screening. But breast MRI may be recommended if:

  • You're at high risk of breast cancer, defined as a lifetime risk of 20 percent to 25 percent or greater.
  • You've been diagnosed with breast cancer and your doctor wishes to determine the extent of the cancer.
  • Your doctor finds a suspicious area on your mammogram.
  • You or your doctor can feel a mass or other lump in your breast, but it's not detectable on mammogram or ultrasound.
  • You notice a breast lump or other breast change after breast surgery or radiation therapy and it's not detectable on mammogram or ultrasound.
  • Your doctor wants to monitor your opposite breast after you've been newly diagnosed or treated for breast cancer in the other breast.
  • You have a suspected leak or rupture of a breast implant.
  • You have a strong family history of breast cancer or ovarian cancer.
  • You received chest radiation for Hodgkin's disease before age 30.
  • You have very dense breast tissue and your prior breast cancer wasn't detected on mammogram.
  • You have a history of precancerous breast changes, a strong family history of breast cancer and dense breast tissue.

If you're unsure whether you're considered high risk, ask your doctor to help you determine your personal risk estimate.

Breast MRI is best used in addition to a mammogram or other breast-imaging test — not as a replacement for a mammogram. Although it's a very sensitive test, breast MRI can still miss some breast cancers that a mammogram will detect.

How do you prepare for a breast MRI?

When possible, schedule your breast MRI at a facility that can also perform MRI-guided breast biopsies. That way, if you need a biopsy — a test that takes tissue samples to evaluate a suspicious area in your breast — it can be done at the same time. Otherwise you might have to repeat the MRI at the time of a breast biopsy at a different facility.

If you're premenopausal, the MRI facility may prefer to schedule your MRI at a certain point during your menstrual cycle, around days seven to 14. Let the facility know where you are in your cycle so that optimal timing for the breast MRI can be arranged.

Follow any special instructions that you receive when you make the appointment for the imaging test. Tell the MRI facility if you have a cardiac pacemaker or other electronic device implanted in your body or if you're pregnant or think you may be pregnant. MRI generally isn't recommended in these circumstances.

How is a breast MRI done?

MRI uses a magnetic field and radio waves to create a composite, 3-D image of your breast. Any 2-D plane (slice) can be electronically created from this image and displayed on a video monitor.

What can you expect during a breast MRI?

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 during the test. If you have trouble being in a small, confined space, you may be given a mild sedative.

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.

A contrast agent (dye) may be injected into your veins through an intravenous (IV) line in your arm to enhance the appearance of tissues or blood vessels on the MRI pictures. If a contrast agent is used, your doctor may test your kidney function beforehand and may also discuss the benefits and risks of using a contrast agent during the MRI.

During the test, the technologist monitors you from another room. You can speak to the technologist through a microphone and you'll also have a hand-held alarm to use to contact the technologist. You'll be instructed to breathe normally but to lie as still as possible.

The breast MRI appointment may take up to one hour.

Breast MRI

Illustration showing a woman undergoing breast MRI

During a breast MRI, you lie on your stomach on a padded scanning table. Your breasts fit into a hollow depression in the table, which contains coils that detect magnetic signals. The table slides into the large opening of the MRI machine.

Results

A radiologist — a doctor specializing in imaging techniques — reviews the images from your MRI, and a member of your health care team will contact you to discuss the results of the test.

To support tumor growth, cancerous tissue often has a greater blood supply than normal tissue does. On an MRI image, more contrast appears in areas of increased blood supply. The radiologist can tell which areas may be cancerous based on the amount of contrast that appears.

However, MRI can't always separate noncancerous (benign) areas from cancerous areas. Additional ultrasound exams or mammograms, and possibly a biopsy, may be needed after a breast MRI to determine if cancer is present.

Benefits and risks

There aren't any known harmful effects from exposure to the magnetic fields or radio waves used to create the images in a breast MRI.

Just as with other tests, a breast MRI has benefits and limits. One benefit is that MRI is very good at detecting invasive breast cancers, even if you have dense or fibrous breast tissue. One limit is that an MRI may identify suspicious areas that, after further evaluation, 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.

Finally, another thing to consider is the cost of breast MRI — it's expensive. In some cases, insurance companies won't cover the expense of the test, so you may have to pay out-of-pocket — $1,000 or more — for the exam. Before having a breast MRI, check with your insurance company to see whether you'll be covered.

Last Updated: 07/23/2007
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