Breast MRI (Magnetic Resonance Imaging)
MRI, or magnetic resonance imaging, is a technology that uses magnets and radio waves to produce detailed cross-sectional images of the inside of the body. MRI does not use X-rays, so it does not involve any radiation exposure. Breast MRI has a number of different uses for breast cancer, including:
screening high-risk women (women known to be at higher than average risk for breast cancer, either because of a strong family history or a gene abnormality)
gathering more information about an area of suspicion found on a mammogram or ultrasound
monitoring for recurrence after treatment
How breast MRI is performed
Unlike a mammogram, which uses X-rays to create images of the breast, breast MRI uses magnets and radio waves to produce detailed 3-dimensional images of the breast tissue. Before the test, you may need to have a contrast solution (dye) injected into your arm through an intravenous line. Because the dye can affect the kidneys, your doctor may perform kidney function tests before giving you the contrast solution. The solution will help any potentially cancerous breast tissue show up more clearly. Some people experience temporary discomfort during the infusion of the contrast solution.
Cancers need to increase their blood supply in order to grow. On a breast MRI, the contrast tends to become more concentrated in areas of cancer growth, showing up as white areas on an otherwise dark background. This helps the radiologist determine which areas could possibly be cancerous. More tests may be needed after breast MRI to confirm whether or not any suspicious areas are actually cancer.
For the breast MRI, you will need to pull down your hospital gown to your waist or open it in front to expose your breasts. Then you lie on your stomach on a padded platform with cushioned openings for your breasts. Each opening is surrounded by a breast coil, which is a signal receiver that works with the MRI unit to create the images. The platform then slides into the center of the tube-shaped MRI machine. You won’t feel the magnetic field and radio waves around you, but you will hear a loud thumping sound. You will need to be very still during the test, which takes around 30 to 45 minutes. If you’re claustrophobic, being confined within an MRI machine for a long period of time can be difficult. Some facilities have an open MRI machine to avoid this problem, or you may be given a mild sedative.
Because the technology uses strong magnets, it is essential that you remove anything metal — jewelry, snaps, belts, earrings, zippers, etc. — before the test. The technologist also will ask you if you have any metal implanted in your body, such as a pacemaker or artificial joint.
Where to have breast MRI
It’s important to have breast MRI done at a facility with:
MRI equipment designed specifically for imaging the breasts. Not all hospitals and imaging centers have this; instead, many have MRIs used for scanning the head, chest, or abdomen.
The ability to perform MRI-guided breast biopsy. If the breast MRI reveals an abnormality, you’ll want to have an MRI-guided breast biopsy (a procedure to remove any suspicious tissue for examination) right away. Otherwise, you’ll need to have a breast MRI again at another facility that offers an immediate MRI-guided breast biopsy.
If your doctor recommends that you have breast MRI for screening, diagnosis, or follow-up, ask for help in finding the best place to have the test done. The American College of Radiology is working on a system for accrediting breast MRI centers, which should make it easier to find high-quality breast MRI facilities in the future.
Breast MRI for screening
Breast MRI is not recommended as a routine screening tool for all women. However, it is recommended for screening women who are at high risk for breast cancer, usually due to a strong family history and/or a mutation in genes such as BRCA1 or BRCA2. If you are considered high-risk, you would have breast MRI in addition to your annual mammograms (X-rays of the breast).
Breast MRI is not a perfect tool. Although it is generally considered more sensitive for picking up breast cancer than mammography, it also can miss some cancers that would be detected by mammography. That is why breast MRI is recommended only in combination with other tests, such as mammogram or ultrasound.
Yearly mammograms plus breast MRI screening are typically recommended for women who are at higher-than-average risk of developing breast cancer — in other words, at greater than the average 13% risk most women have over the course of an entire lifetime.
The American Cancer Society (ACS) recommends that all high-risk women — those with a greater than 20% lifetime risk of breast cancer — have a breast MRI and a mammogram every year. For most women, these combined screenings should start at age 30 and continue as long as the woman is in good health. According to ACS guidelines, high-risk women include those who:
have a known BRCA1 or BRCA2 gene mutation
have a first-degree relative (mother, father, brother, sister, or child) with a BRCA1 or BRCA2 gene mutation and have not had genetic testing themselves
find out they have a lifetime risk of breast cancer of 20-25% or greater, according to risk assessment tools that are based mainly on family history
had radiation therapy to the chest for another type of cancer, such as Hodgkin’s disease, when they were between the ages of 10 and 30 years
have a genetic disease such as Li-Fraumeni syndrome, Cowden syndrome, or Bannayan-Riley-Ruvalcaba syndrome, or have one of these syndromes in first-degree relatives
The American Cancer Society also recommends that women at moderately increased risk of breast cancer — those with a 15-20% lifetime risk — talk with their doctors about the possibility of adding breast MRI screening to their yearly mammogram. According to ACS guidelines, this includes women who:
find out they have a lifetime risk of breast cancer of 15-20%, according to risk assessment tools based mainly on family history
have a personal history of breast cancer, ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS), or abnormal breast cell changes such as atypical ductal hyperplasia or atypical lobular hyperplasia
have extremely dense breasts or unevenly dense breasts when viewed by mammograms
If you think you’re a candidate for breast MRI screening, talk to your doctor. You and your doctor may need to work with your health insurance plan to get the test covered. You may have to prove to your plan that you are indeed considered high-risk for breast cancer. You also will need to find a facility with dedicated breast MRI screening equipment.
For more information about breast cancer risk, visit the Know Your Risk section.
Breast MRI is not recommended as a screening tool for women who are at average risk of developing breast cancer. Yes, breast MRI has been found to be more sensitive in detecting cancers than mammograms, which does seem like an advantage. However, a major disadvantage is that breast MRI screening results in more false positives — in other words, the test finds something that initially looks suspicious but turns out not to be cancer. If breast MRI were adopted as a screening tool for everyone, many women would end up having unnecessary biopsies and other tests, not to mention the anxiety and distress. That is why current recommendations reserve breast MRI screening for high-risk women only.
MRI is also more expensive than mammography, and dedicated breast MRI screening equipment is not widely available.
Breast MRI for diagnosis and monitoring
The value of breast MRI for breast cancer detection remains uncertain. Some doctors believe MRI can distinguish a breast cancer from normal breast gland tissue better than other techniques. But breast MRI is expensive and requires highly specialized equipment and highly trained experts. Relatively few breast MRI centers exist, especially outside of major cities. And even at its best, MRI produces many uncertain findings. Some radiologists call these “unidentified bright objects,” or UBOs. MRI also cannot detect calcifications (calcium deposits in breast tissue that could be a sign of cancer). Finally, MRI can dislodge certain metal devices, such as pacemakers, in some people.
In some situations, however, breast MRI can be useful in gathering more information about an area in the breast that is suspicious or already confirmed to be cancerous. Possible uses include:
evaluating a person who has a palpable mass (a mass that can be felt) that isn’t visible with ultrasound or mammography
evaluating a lesion in the densely glandular breast of a young woman. Young women tend to have dense breast tissue, which makes it difficult to see abnormal areas on imaging studies.
evaluating a person who has breast cancer cells in an underarm lymph node, but no breast mass that doctors are able to feel or to see on a mammogram. In these cases, where mastectomy is typically recommended, MRI can help find the precise site of the cancer’s origin within the breast. Finding the cancer’s site of origin can expand a woman’s treatment options from only mastectomy to include lumpectomy plus radiation.
determining if a cancer is limited to one area of the breast, or if it is “multicentric” and involves more than one area. Knowing this affects treatment choices, since mastectomy is necessary for multicentric disease. MRI can be particularly useful for women with invasive lobular cancer, which has a tendency to be diffuse or multicentric.
checking a woman’s other breast for signs of cancer after she receives her initial cancer diagnosis. The American Cancer Society recommends that breast MRI be used to check the other breast for any signs of cancer.
examining breast tissue in women who have had silicone breast implants. MRI scanning can detect leakage from a silicone-filled breast implant, since it easily distinguishes silicone gel from surrounding normal breast and chest wall tissues.
After treatment for breast cancer, MRI can be useful for checking scar tissue in women who have undergone lumpectomy. Any significant changes could suggest a return of the breast cancer.
Finally, MRI scans of other parts of the body — such as the brain, spinal cord, or bones — may be useful in people who are known or suspected to have metastatic breast cancer (cancer that has traveled outside the breast to other areas of the body). For example, a person who has progressive back pain, or who develops new weakness or numbness in the arms or legs (not just hands or feet), can have an MRI scan of her back. The scan can help identify serious conditions such as the possible presence of a spinal tumor or brain metastasis.
— Last updated on July 27, 2022, 1:53 PM