Breast MRI: What you need to know
What is a breast MRI used for?
If the person needs to move or take a break during an MRI, it is best to alert the technician so that the scan results are not affected.
A breast MRI is predominately used to determine the stage of cancer by measuring the size and extent of cancerous tissues after breast cancer has been diagnosed.
Because they do not use ionizing radiation, MRI scans are also commonly used to evaluate breast tissues in women who should not be exposed to radiation.
Common uses for breast MRI scans include:
- looking for additional tumors or suspicious tissues in the breasts after a breast cancer diagnosis
- assessing breast tissues in women under the age of 25, or those with dense breast tissue
- confirming the results of other imaging tests, most commonly mammogram or ultrasound
- assessing breast tissues in pregnant or breast-feeding women
- monitoring the effectiveness of chemotherapy
- monitoring the tissues around the area where cancerous tumors or tissues were removed by surgery or chemotherapy
- assessing breast implants for damage and leakage
- monitoring healing in women who have had reconstructive surgery
A breast MRI is not included in routine breast cancer screening plans for the majority of women.
For people considered at a high risk of breast cancer, the test can be used in combination with a mammogram, as an early screening tool.
There are many reasons for someone to benefit from routine breast MRI scans. Those reasons include:
having a 20 percent or more lifetime risk of developing breast cancer, calculated scientifically using family history
- having a BRCA1 or BRCA2 gene mutation
- having an immediate family member, such as parent, sibling, or child, with the BRCA1 or BRCA2 gene mutation
- having Li-Fraumeni syndrome or an immediate family member with it
- having Bannayan-Riley-Ruvalcaba syndrome or an immediate family member with it
- having Cowden syndrome or an immediate family member with it
- having a history of radiation exposure to the chest
A breast MRI may be used to establish the stage of breast cancer.
Image credit: National Cancer Institute, (1994, February).
Breast MRI scans are usually done in a specialty clinic or department of a hospital.
An MRI machine with dedicated breast coils is preferred for breast scans. Not all facilities have this machine, so it is a good idea to check online or call ahead and ask.
General use MRI machines are more likely to miss fine details in breast tissues. If a biopsy is required, the test will need to be repeated using the specialized machine.
For people with claustrophobia or a fear of enclosed spaces, it may be useful to go and see the machine before the scan.
Occasionally, an open MRI machine may be available. Anti-anxiety medications or sedatives can be given immediately before the test for people unable to relax.
A health care professional will often help position individuals on the MRI table and will be able to hear and see what is going on during the actual scan. However, they will leave the room once the MRI starts.
For premenopausal women, the test is best done between day 7 and 10 of the mensuration cycle.
How to prepare
There are no specific medical instructions on how to prepare for a breast MRI.
Metal objects can affect MRI magnets, ruin an image, and potentially lead to physical injury and damage to the machine. So, it is a good idea to leave jewelery, watches, belts, and zippered clothing at home.
People with metal objects in their bodies, such as pacemakers, piercings, dental work, or cochlear implants will either need to have them removed before the scan or be tested using another imaging technique.
The MRI machine is quite noisy. Most people say the whirling, clicking, and bumping noises resemble a loud washing machine. Some clinics will provide earplugs or music to drown out the sound.
What to expect during the procedure
A breast MRI is usually performed with the patient laying on their front, with a gap in the bed for the breasts.
MRI images are created using the help of a contrasting dye called gadolinium. The dye is injected into a vein in the arm shortly before the test.
Some people have an adverse reaction to the dye, so it is important to let the attending doctor know of any previous allergic reactions to contrast dyes.
People with kidney or liver conditions need to undergo additional testing before the dye can be safely used.
Most breast MRI scans begin with the woman undressing and changing into a hospital gown, then lying face down on the MRI table. There are two holes on the table that the breasts fit into, allowing them to hang uncompressed.
A technician or nurse will then help guide the body and breasts into the correct position, often using a pillow or prop for support. These aids also help prevent movement during the scan.
Once the body is properly positioned, the technician or nurse will leave the room. The MRI table will then start to slowly move back into a narrow tube in the middle of the machine until the person is completely enclosed.
In total, a breast MRI usually takes 30 minutes to 1 hour to complete.
Staying absolutely still while the image is captured is very important. But each picture should only take a few minutes. The technician will normally spread out the imaging sessions into several minute periods, allowing movement breaks in between.
It is important to tell the technician if a break is needed rather than risk ruining the results by moving or fidgeting.
Usually, the technician will take a few minutes to check the images after the scan is done, to ensure no additional scanning is needed.
The results will then usually be written up in a report and sent to the doctor who ordered the test, who will then schedule an appointment to discuss the results.
On MRI images, cancerous tissues tend to appear as abnormally white areas with a dark or black background.
The most common risk is that the test will generate a false positive result, identifying normal tissues as concerning or suspicious.
False positives can cause unnecessary anxiety and trigger the need for further, more invasive tests, such as a biopsy. Invasive testing is known to increase the risk of tissue, nerve, or blood vessel damage.
Because of these risks, breast MRI scans are not recommended for women who have not been diagnosed with breast cancer or those without a high risk of developing it.