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Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI) is a procedure that is sometimes used to further evaluate breast cancer. MRI is non-invasive, does not use radiation and can be done as an outpatient. The MRI machine uses powerful magnets that spin in a circular motion as you lay on the exam table, similar to a CT scan. The magnets detect the density of hydrogen molecules in various tissues of your body and use this data to construct a 3-D image of your entire body or in this case just the breasts.

 The Use of MRI in Screening for Breast Cancer

Magnetic Resonance Imaging is useful in the management of breast cancer, but its role in routine screening is still unclear. It seems to be most beneficial in those with a very high risk for breast cancer based on family history, defined by the American Cancer Society as a 20-25% increased risk over the general population and those who may have bilateral breast cancer. [1]A study from the New England Journal of Medicine revealed that MRI performed in women who had been diagnosed with breast cancer in one breast, detected over 90% of the cancers that were already present in the other breast and were initially missed by mammography or clinical breast exam.[2] The American Cancer Society gave the following recommendations for the use of MRI in breast cancer screening:[3]

  • Annual MRI for women that have the BRCA1 or BRCA2 genetic mutations, or have a first degree relative that carries the mutation
  • Women with a lifetime risk of developing breast cancer that is 20 -25 % higher than the general population, based on family history
  • Use in women who have had breast implants

The MRI Unit

The MRI unit is very similar to a CT scanner, as it has a platform or table that the patient lays on while it is passed through a cylinder-shaped structure. The difference is that the cylinder-shaped structure used in CT emits radiation, where the one on MRI uses powerful magnets instead. [4] Short bore or open-MRI units are available at some institutions and have a U-shaped structure. These are best for patients who are claustrophobic or cannot fit into a typical MRI unit. Most MRI’s are done with the patient lying on their back. However, breast MRI is done with the patient lying on their front with the breast being allowed to fall through an opening. This allows for all structures within the breast to be imaged clearly.

The data that is gathered by the magnets are transmitted onto a screen creating a very clear image. This image may be superior to that of a CT scan for certain types of exams, particularly those that wish to evaluate soft tissues.[5]

The Procedure

When you arrive for the procedure you will be given a gown to wear and you will be asked to remove all jewelry. It is best to leave watches, rings, earrings and other valuable items at home if possible. Removable dental appliances should be removed. You will be given a questionnaire concerning your medical history and prior surgeries. It is important to note any surgery that may have involved use of implantable metal devices, such as pacemakers, rods or screws. It is also important to note the potential for metallic objects to be imbedded in your body, such as shrapnel, bullets or even small bits of metal from welding.


Further studies are being done to determine the role of MRI in breast cancer management. At this time, it appears to be most useful for those who have a very high risk for developing breast cancer, have unilateral breast cancer and wish to evaluate for bilateral disease, and those who have had breast implants, making mammogram a risk for implant rupture.


1  Young, K. (2007). ACS Urges MRI Breast Screens for Women in High Risk Category. Medical Device Week .

2  Ibid

3 Ibid

4  MRI of the Breast. (n.d.). Retrieved from Radiology Info:

5  Ibid

This article was originally published on July 27,2012 and last revision and update of it was 9/2/2015.