A breast MRI uses magnetic fields and radio waves to create cross-sectional images of the soft tissues in the breast.
A breast MRI helps a doctor determine the stage of cancer by measuring the size and spread of cancerous tissues.
As MRIs do not use ionizing radiation, doctors also use them to evaluate breast tissues in women who have a high risk of cancer or who should avoid radiation.
Common uses for MRI scans of the breast include:
- looking for additional tumors or suspicious tissues in the breasts after a cancer diagnosis
- evaluating breast tissue in women under 25 years old
- examining dense breast tissue
- confirming the results of other imaging tests, such as a mammogram or ultrasound
- assessing breast tissues in women who are pregnant or breastfeeding
- monitoring the effectiveness of chemotherapy
- monitoring tissue around a site where surgery or chemotherapy have removed cancerous tumors
- assessing breast implants for damage and leakage
- monitoring healing in women who have had reconstructive surgery
Most women will not undergo a breast MRI as a routine scan.
For people who have a high risk of breast cancer, doctors may combine a breast MRI with a mammogram as an early screening tool. For people with a previous diagnosis of breast cancer, especially younger individuals with dense breasts, doctors may alternate MRIs with mammograms for follow-up screening.
Reasons to have a breast MRI
A doctor may recommend routine breast MRI screening for many reasons, including:
- having a BRCA1 or BRCA2 gene mutation
- having a 20% or higher lifetime risk of developing breast cancer, which a doctor calculates using family history
- having an immediate family member, such as parent, sibling, or child with the BRCA1 or BRCA2 gene mutation
- having a history of radiation exposure to the chest
People should also consider a breast MRI, during routine screening, if they or an immediate family member have one of the following conditions:
- Li-Fraumeni syndrome
- Bannayan-Riley-Ruvalcaba syndrome
- Cowden syndrome
Breast MRI scans usually take place in a specialized radiology facility or a hospital's or clinic's radiology department.
An MRI machine with dedicated breast coils is preferable for breast scans.
Not all facilities have a machine with this feature, so it is a good idea to check online or call ahead of the appointment and ask.
General use MRI machines are more likely to miss fine details in breast tissues.
If a biopsy is necessary after using a less specialized machine, the doctor will need to request another scan using an MRI machine with breast coils.
For people with claustrophobia or a fear of enclosed spaces, it may be useful or soothing to see the machine before the scan to become comfortable with its appearance. Occasionally, an open MRI machine may be available.
A doctor can administer anti-anxiety medications or sedatives before the test for people who cannot relax sufficiently to enter the machine.
A healthcare professional will often help position individuals on the MRI table and can hear and see what is going on during the scan. However, they will leave the room once the MRI starts.
For people who are premenopausal, it is best if healthcare professionals do the test between day 7 and day 10 of the individual's mensuration cycle.
There are no specific medical instructions on how to prepare for a breast MRI.
Metal objects can affect MRI magnets, ruin the final image, and potentially cause physical injury and damage to the machine.
It is a good idea for people to avoid wearing jewelry, watches, belts, and clothing that has zippers, as they will have to remove these prior to the MRI.
A person with metal objects in their body on a permanent or semipermanent basis, such as a pacemaker, piercings, dental work, or cochlear implants, will need to have a doctor remove them before the scan or request another imaging technique.
The MRI machine makes loud noises. Many people say the whirling, clicking, and bumping sounds resemble a loud washing machine. Some clinics will provide earplugs or music to block the sound.
Here, learn about ultrasound, another scan that can help a doctor diagnose breast cancer.
An MRI scanner creates images using a contrasting dye called gadolinium. The doctor injects the dye into a vein in the arm shortly before the test.
Some people have an adverse reaction to the dye. It is important to let the attending doctor or healthcare professional know of any previous allergic reactions to contrast dyes.
In some cases, an MRI may be necessary with the contrast dye, though an MRI with contrast is more typical for breast cancer screening.
People with kidney or liver conditions need to undergo additional testing before a doctor can safely administer the dye.
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 into which the breasts fit, allowing them to fall with pressure.
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.
After correctly positioning the body, the technician or nurse will leave the room. The MRI table will then start to slowly enter a narrow tube in the middle of the machine and completely enclose the person.
In total, a breast MRI usually takes between 30 and 60 minutes to complete.
Remaining absolutely still while the machine captures the image is crucial. However, each picture should only take a few minutes. The technician will normally spread out the imaging sessions into several periods, allowing movement breaks in between.
It is important to let the technician know if a break is necessary rather than risk ruining the results by moving or fidgeting.
The technician will usually take a few minutes to check the images after completion to ensure they do not need to make any extra scans.
They will then write up the results in a report and send them to the individual's doctor. The doctor will then communicate 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 suspicious or of concern.
False-positives can cause unnecessary anxiety and trigger the need for a further, more invasive test, such as a biopsy.
Invasive testing may increase the risk of tissue, nerve, or blood vessel damage. Doctors do not recommend a breast MRI for women who do not have a breast cancer diagnosis or those without a high risk of developing the disease because of these risks.
Do doctors ever use CT scans to diagnose breast cancer?
Doctors do not typically use CT scans to screen for cancer in the breasts. They may use CT scans to determine whether breast cancer has spread to the chest wall or other parts of the body.
Yamini Ranchod, PhD, MS Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.