Breast Magnetic Resonance Imaging (MRI)
(MRI Scan of the Breast)
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What is magnetic resonance imaging (MRI)?
Magnetic resonance imaging (MRI) is a diagnostic procedure that uses a combination of a large magnet, radio waves, and a computer to produce detailed images of organs and structures within the body.
How does an MRI work?
The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient. The magnetic field, along with radio waves, alters the hydrogen atoms' natural alignment in the body. Computers are then used to form a two-dimensional (2D) image of a body structure or organ based on the activity of the hydrogen atoms. Cross-sectional views can be obtained to reveal further details. MRI does not use radiation, as do X-rays or computed tomography (CT scans).
A magnetic field is created and pulses of radio waves are sent from a scanner. The radio waves knock the nuclei of the atoms in your body out of their normal position. As the nuclei realign into proper position, they send out radio signals. These signals are received by a computer that analyzes and converts them into an image of the part of the body being examined. This image appears on a viewing monitor. Some MRI machines look like narrow tunnels, while others are more open.
How does a breast MRI work?
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For a breast MRI, the woman usually lies face down, with her breasts positioned through openings in the table. In order to check breast positioning, the technologist watches the MRI through a window while monitoring for any potential movement.
A breast MRI usually requires the use of contrast that is injected into a vein in the arm before or during the procedure. The dye may help create clearer images that outline abnormalities more easily.
MRI, used with mammography and breast ultrasound, can be a useful diagnostic tool. Recent research has found that MRI can locate some small breast lesions sometimes missed by mammography. It can also help detect breast cancer in women with breast implants and in younger women who tend to have dense breast tissue. Mammography may not be as effective in these cases. Since MRIs do not use radiation, they may be used to screen women younger than 40 and to increase the number of screenings per year for women at high risk for breast cancer.
Although it has distinct advantages over mammography, breast MRI also has potential limitations. For example, it is not always able to distinguish the difference between cancerous abnormalities, which may lead to unnecessary breast biopsies. This is often referred to as a "false positive" test result.
Recent research has demonstrated that using commercially available software programs to enhance breast MRI scans can reduce the number of false positive results with malignant tumors. Thus, the need for biopsies may decrease with computer-aided enhancement.
Another disadvantage of breast MRI is that it has historically been unable to identify calcifications or tiny calcium deposits that can indicate breast cancer.
Reasons for the procedure
The most recent guidelines from the American Cancer Society include screening MRI with mammography for certain high-risk women. This option should be considered for the following:
Women with BRCA1 or BRCA2 mutation (BRCA1 is a gene, which, when altered, indicates an inherited susceptibility to cancer. BRCA2 is a gene, which, when altered, indicates an inherited susceptibility to breast and/or ovarian cancer.)
Women with a first-degree relative (mother, sister, and/or daughter) with a BRCA1 or BRCA2 mutation, if they have not yet been tested for the mutation
Women with a 20% to 25% or greater lifetime risk of breast cancer, based on 1 of several accepted risk assessment tools that look at family history and other factors
Women who have had radiation treatment to the chest between the ages of 10 and 30, such as for treatment of Hodgkin disease
Women with the genetic disorders Li-Fraumeni syndrome, Cowden syndrome, or Bannayan-Riley-Ruvalcaba syndrome; or those who have a first degree relative with the syndrome
Some common uses for breast MRI include:
Further evaluation of abnormalities detected by mammography
Finding early breast cancers not detected by other tests, especially in women at high risk and women with dense breast tissue
Examination for cancer in women who have implants or scar tissue that might produce an inaccurate result from a mammogram This test can also be helpful for women with lumpectomy scars to check for any changes.
Detecting small abnormalities not seen with mammography or ultrasound (for example, MRI has been useful for women who have breast cancer cells present in an underarm lymph node, but do not have a lump that can be felt or can be viewed on diagnostic studies)
Assess for leakage from a silicone gel implant
Evaluate the size and precise location of breast cancer lesions, including the possibility that more than one area of the breast may be involved (this is helpful for cancers that spread and involve more than one area)
Determining whether lumpectomy or mastectomy would be more effective
Detecting changes in the other breast that has not been newly diagnosed with breast cancer (There is an approximately 10 percent chance that women with breast cancer will develop cancer in the opposite breast. A recent study indicates that breast MRI can detect cancer in the opposite breast that may be missed at the time of the first breast cancer diagnosis.)
Detection of the spread of breast cancer into the chest wall, which may change treatment options
Detection of breast cancer recurrence or residual tumor after lumpectomy
Evaluation of a newly inverted nipple change
There may be other reasons for your health care provider to recommend breast MRI.
Risks of the procedure
Because radiation is not used, there is no risk of exposure to radiation during an MRI procedure.
Each patient must be screened before exposure to the MRI magnetic field. Due to the use of the strong magnet, MRI cannot be performed on patients with implanted pacemakers, older intracranial aneurysm clips, cochlear implants in the ear, certain prosthetic devices, implanted drug infusion pumps, neurostimulators, bone-growth stimulators, certain intrauterine contraceptive devices, or any other type of iron-based metal implants. MRI is also contraindicated in the presence of some internal metallic objects, such as bullets or shrapnel, as well as surgical clips, pins, plates, screws, metal sutures, or wire mesh.
If you are pregnant or suspect that you may be pregnant, you should notify your health care provider. Due to the potential for a harmful increase in the temperature of the amniotic fluid, MRI is not advised for pregnant patients.
If contrast is used, there is a risk for allergic reaction. Patients who are allergic to or sensitive to medications, contrast dye, or iodine should notify the radiologist or technologist.
There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your health care provider prior to the procedure.
Before the procedure
Your health care provider will explain the procedure to you and offer the opportunity to ask any questions that you might have about the procedure.
If your procedure involves the use of contrast, you will be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if something is not clear.
Personal items, such as your watch, wallet, including any credit cards with a magnetic strip (which may be erased by the magnet), will be left in a locker or other secure place prior to the MRI scan.
Before the examination, it is extremely important that you inform the technologist if any of the following apply to you:
You are claustrophobic and think you will be unable to lie still while inside the scanning machine, in which case you may be given a sedative
You have a pacemaker or have had heart valves replaced
You have any type of implantable pump, such as an insulin pump
You have metal plates, pins, metal implants, surgical staples, or aneurysm clips
You have metallic fragments anywhere in the body
You have permanent eye liner or tattoos
You are pregnant or suspect you may be pregnant
You ever had a bullet wound
You have ever worked with metal (for example, a metal grinder or welder)
You have any body piercing
You are wearing a medication patch
You are not able to lie down for 30 to 60 minutes
As there is a possibility that you may receive a sedative before the procedure, you should plan to have someone drive you home afterwards.
Based on your medical condition, your health care provider may require other specific preparation.
During the procedure
MRI may be performed on an outpatient basis or as part of your stay in the hospital. Procedures may vary depending on your condition and your health care provider's practices.
Generally, a breast MRI follows this process:
You will be asked to remove any clothing, jewelry, eyeglasses, hearing aids, hairpins, removable dental work, or other objects that may interfere with the procedure.
You will be given a hospital gown to wear.
If you are to have a procedure done with contrast, an intravenous (IV) line will be started in the hand or arm for injection of the contrast.
You will be positioned, face down on a mobile bed, with your breasts positioned through cushioned openings. The bed will then be moved into the magnet of the MRI machine. Pillows or straps may be used to prevent movement during the procedure.
The technologist will be in a separate room inside the larger MRI room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner will enable the technologist to communicate with and hear you. You will have a call button so that you can let the technologist know if you have any problems during the procedure. The technologist will be watching you at all times and will be in constant communication.
You will be given earplugs or a headset to wear to help block out the noise from the scanner. Some headsets may provide music for you to listen to.
During the scanning process, a loud clicking noise will sound as the magnetic field is created and pulses of radio waves are sent from the scanner.
It will be important for you to remain very still during the examination, as any movement could cause distortion and affect the quality of the scan.
At intervals, you may be instructed to hold your breath for a few seconds, depending on the views of the breasts being examined.
If contrast is used for your procedure, you may feel some effects when the dye is injected into the IV line. These effects include a flushing sensation or a feeling of coldness, a salty or metallic taste in the mouth, a brief headache, itching, or nausea and/or vomiting. These effects usually only last for a few moments.
Your breasts may feel slightly warm, but this is normal.
You should notify the technologist if you have any breathing difficulties, sweating, numbness, or heart palpitations.
Once the scan has been completed, the table will slide out of the scanner and you will be assisted off the table.
If an IV was inserted for contrast administration, it will be removed.
While the MRI procedure itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure such as surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.
After the procedure
You should move slowly when getting up from the scanner table to avoid any dizziness or lightheadedness from lying prone for the length of the procedure.
If any sedatives were taken for the procedure, you may be required to rest until the sedatives have worn off. You will also need to avoid driving.
If contrast was used during your procedure, you may be monitored for a period of time for any side effects or reactions to the contrast, such as itching, swelling, rash, or difficulty breathing.
If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your health care provider, as this could indicate an infection or other type of reaction.
Nursing mothers may choose not to breastfeed for 12 to 24 hours after a breast MRI with contrast.
Generally, there is no special type of care required after a MRI scan of the breasts. You may resume your usual diet and activities, unless your health care provider advises you differently.
A radiologist will analyze the images and provide a report to your health care provider.
Your health care provider may give you additional or alternate instructions after the procedure, depending on your particular situation.
The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your health care provider. Please consult your health care provider with any questions or concerns you may have regarding your condition.
This page contains links to other websites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these websites, not do these sites endorse the information contained here.
Centers for Disease Control and Prevention (CDC)
National Alliance of Breast Cancer Organizations
National Breast and Cervical Cancer Early Detection Program
National Breast Cancer Awareness Month
National Breast Cancer Coalition
National Breast Cancer Foundation
National Institutes of Health (NIH)
NIH - Office of Research on Women's Health
Susan G. Komen For the Cure
- Freeborn, Donna, PhD, CNM, FNP
- MMI board-certified, academically affiliated clinician