Definition & Overview

An MRI, or a Magnetic Resonance Imaging scan, is a non-invasive medical test used to obtain detailed images of different body parts using a powerful magnetic field. Instead of radiation, which is typically used in other imaging techniques, MRI uses radiofrequency pulses to take detailed pictures showing the body’s soft tissues, organs, bone, and internal structures. Its main purpose is to help physicians observe and evaluate certain body parts and to diagnose the presence of a particular disease or to confirm an initial diagnosis.

One of the body parts that can undergo the MRI test is the breast. When performed on this body part, the goal of an MRI is typically to diagnose breast cancer and other abnormalities. It is also often performed after a biopsy confirms the presence of cancer in which case, MRI scan is used to determine the stage of cancer.

Due to its differences from other imaging scans, such as the x-ray or ultrasound, an MRI can provide additional crucial information that cannot be obtained using other types of scans. It is, however, not a replacement for a mammogram; instead, it is usually used alongside a mammogram or ultrasound to ensure the accuracy of the diagnosis.

Who Should Undergo & Expected Results

An MRI of the breast is advisable or prescribed for:

  • Women who are at risk of having breast cancer due to medical family history – Since breast cancer is hereditary, women whose mothers and/or sisters have had breast and/or ovarian cancer under the age of 50, are considered to have a naturally and genetically increased risk of also having the condition/s. Nowadays, women are taking a more pro-active stance against breast cancer, and may seek treatment even when the cancer has not occurred yet; an MRI can help with this.

  • Patients who were diagnosed with breast cancer - A breast MRI is also performed on people who were diagnosed with breast cancer to determine the stage of cancer. An MRI can help determine the size of the tumour, whether an underlying muscle is involved, if there are other types of cancer present in the breast, or if there are large lymph nodes in the armpit, which may indicate that the cancer has spread to that area.

  • Patients who need more information about the breast following a mammogram – MRI is typically ordered as a follow-up scan when the results of mammogram show abnormalities.

  • Patients who have already undergone treatment for breast cancer – An MRI of the breast is often used to evaluate the lumpectomy sites years after treating breast cancer to observe if the cancer has come back or has any chance of recurring. It is necessary to use MRI for this purpose because a mammogram or regular physical exam cannot differentiate scarring cancer from a recurrence.

  • Patients undergoing neoadjuvant chemotherapy - Chemotherapy performed prior to a removal surgery is called neoadjuvant chemotherapy. Patients who are undergoing this type of treatment often undergo a breast MRI to observe the chemotherapy’s effect on the tumour and to determine if it is working.

  • Patients who need post-surgical evaluation for silicone breast implants - Women who have silicone breast implants may need an MRI of the breast to determine if the silicone breasts have ruptured.

How Does the Procedure Work?

An MRI of the breast is performed using an MRI scanner, which is a large cylinder-shaped tube with a circular magnet. The patient will be asked to lie on an examination table, which will then slide through the magnetic field. A computer monitor, which is typically located in a separate room, is used to process the information from the scan.

In a breast MRI, a specific platform with openings for the breasts is used to allow the patient to lie face down on it, giving the scanner open access to the breasts. Its purpose is to make sure the breasts will not be compressed during the scan.

An MRI of the breast, unlike x-ray scans, does not use ionizing radiation but radio waves that redirect the alignment of hydrogen atoms, which exist naturally inside our body. As the hydrogen atoms return to their normal alignment, energy is emitted; this energy varies depending on the type of tissue that emitted it. The MRI scanner then uses this energy to create an image of the tissues. The procedure does not cause any chemical changes in the body’s tissues.

Information from the MRI unit is transmitted by wire coils, which communicate the radio waves by producing signals that can be detected by other coils and which are processed using a computer to generate a series of images of the breast structure. The scan may entail performing several runs within a span of 30 minutes to an hour. The whole procedure, including preparation, may take a total of 90 minutes.

In some cases, a contrast material may be injected intravenously into a patient’s vein to help in distinguishing cancer tissues.

Possible Complications and Risks

Despite the benefits of a breast MRI and its important role in diagnosing the health of the breasts, the procedure poses some risks and complications, such as:

  • An MRI of the breast makes use of implanted medical devices that contain metal, which can easily cause some health problems in case of malfunction.

  • In cases where a contrast material is used, high doses of the gadolinium-based contrast may potentially cause nephrogenic systemic fibrosis. To avoid these risks, the procedure should be well-planned and thoroughly discussed by both the patient and her attending physician or oncologist, in the case of cancer patients.

  • American Cancer Society recommendations for early breast cancer detection in women without breast symptoms. Last Medical Review: Sept. 17, 2013. Last Revised: Jan. 28, 2014. Available at: Accessed: March 23, 2014.

  • 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.

  • American College of Obstetricians and Gynecologists. Practice Bulletin No. 122 Breast cancer screening. Obstet Gynecol 2011;118:372-82.

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