What Is a Breast MRI?

What to expect when undergoing this test

Doctors examining x-ray
Getty Images/ilbusca

Breast magnetic resonance imaging, also known as a breast MRI, is an imaging technique that uses powerful magnetic and radio waves to generate highly detailed images of breast tissue. Although a breast MRI is not considered a substitute for a mammogram, it has its place in the screening of breast cancer. Breast MRI is also commonly used in the diagnosis and staging of breast cancer.

Purpose of Test

Magnetic resonance imaging (MRI) is a noninvasive imaging technique that neither exposes you to ionizing radiation nor breast compression. When compared to an X-ray, computed tomography (CT), or ultrasound, an MRI provides far greater detail of soft tissues.

A breast MRI is typically used in women who have already been diagnosed with cancer. It can help measure the size of a tumor and check for tumors in the opposite breast. A breast MRI can also be used for breast cancer screening or to monitor your health after cancer treatment.

Screening

A breast MRI can also be used to screen women at a high risk of breast cancer. For this group of women, an MRI would be performed along with a mammogram as part of annual screening. According to the American Cancer Society, "high-risk" is defined as:

  • Having the BRCA1 or BRCA2 gene mutation
  • Having a first-degree relative with the BRCA1 or BRCA2 mutation
  • Having had chest radiation between the ages of 10 and 30
  • Having Li-Fraumeni syndrome, Cowden syndrome, or Bannayan-Riley-Ruvalcaba syndrome which predisposes you cancer (or a first-degree relative with any of these genetic disorders)
  • Having a greater than 20 percent lifetime risk of breast cancer (using a risk assessment tool like the Gail Model designed by scientists at the National Cancer Institute)

Other health risks may be factored in, including a previous history of cancer or precancer, a family history of breast or ovarian cancer, or having especially dense breasts (which can make imaging on a mammogram difficult).

A breast MRI is not recommended for women at standard risk of breast cancer and cannot be used on its own since it may miss abnormalities that a mammogram won't. Furthermore, despite its superior sensitivity, an MRI cannot differentiate between benign and cancerous growths and, as such, is prone to false-positive results.

A 2016 study in Cancer Medicine suggested the false-positive rate with a breast MRI may be as high as 11.9 percent. While a mammogram is far less sensitive, is it also less likely to return a false-positive result.

Diagnosis

A breast MRI is a vital tool in the diagnosis and staging of cancer. It is commonly used when a hard-to-assess abnormality is detected on a mammogram. This may be because breast tissue is especially dense (a situation common in younger women, women with a low body mass index, or those taking hormone therapy for menopause).

Among the other reasons a breast MRI may be used:

  • Determining the extent of cancer after a new diagnosis
  • Staging cancer based on a tumor's size, location, and number
  • Evaluating tumor size after neoadjuvant chemotherapy (chemotherapy intended to shrink a tumor prior to surgery)
  • Evaluating lumpectomy sites in the years following breast cancer treatment 
  • Examining breast implants for leakage or rupture

A breast MRI is also effective at finding unsuspected cancer in the opposite breast, which would allow for early treatment of both tumor sites at once.

Risks and Contraindications

A breast MRI is considered a safe procedure with few side effects. However, it most often requires an intravenous (IV) infusion of a contrast agent, typically one containing the metal gadolinium.

Although gadolinium is not considered toxic and doesn't expose you to radiation, there is a risk of allergy. With that being said, the risk is considered low, ranging from 0.013 percent to 0.22 percent, according to a 2012 study in Radiology.

Gadolinium may also cause nephrogenic systemic fibrosis (NSF), a condition characterized by the thickening or hardening of the skin and other parts of the body. NSF appears largely constrained to people with advanced kidney disease, particularly those with kidney failure, on dialysis, or who have undergone a kidney transplant.

It has also been discovered that gadolinium can establish deposits in the brain. Although the U.S. Food and Drug Administration issued warnings about this effect, it also conceded that it could find "no harmful effects" associated with the deposits.

A breast MRI is contraindicated for use in people with a known allergy to gadolinium or any other ingredient in the contrast agent.

Although an MRI is not contraindicated during pregnancy, you need to inform the technologist if you are pregnant. According to 2017 guidelines from the American College of Obstetricians and Gynecologists (ACOG), the use of gadolinium should be limited during pregnancy due to the lack of safety research. With that being said, ACOG could find no evidence of fetal harm in women exposed to gadolinium versus those who weren't.

Before the Test

If a breast MRI is recommended, advise your doctor if you are claustrophobic or experience anxiety in closed spaces. Unlike some newer MRI units, which have open sides, breast MRIs are enclosed. If needed, your doctor can prescribe a mild sedative like Valium (diazepam), Xanax (alprazolam), or Ativan (lorazepam) to help you relax.

Because MRIs use powerful magnets, you need to advise your doctor about any metals you may have in or on your body. While artificial joints, brain shunts, and artificial heart valves are considered safe, others may be problematic based on the metal type. These include:

It is important to schedule your MRI nearer to the beginning of your menstrual cycle if you are premenopausal. This is because the accuracy of an MRI may be affected by the fluctuation of hormones during your cycle.

If your cycles are regular, the first half—when progesterone levels are low—is usually the best time for a breast MRI. Some facilities will prefer to schedule the MRI between days 7 and 14 of your cycle. When scheduling the appointment, let the facility know where you are in your cycle so that optimal time can be found.

Beyond that, there is little in the way of preparation needed for a breast MRI.

Timing

The scanning portion of the MRI will take only around 30 to 60 minutes to complete. However, with the addition of the gadolinium infusion and the time it takes to change in and out of your clothes, expect to spend no less 2 hours at the facility.

Location

MRIs are performed at hospitals or specialized imaging centers; your doctor will tell you where to go. The actual scan is conducted in one room, while the MRI technologist will operate the machine and capture images from an adjacent control room. You will able to communicate with the technologist via a two-way speaker.

What to Wear

Prior to the infusion and MRI scan, you will be asked to undress into a hospital gown. While there may be a locked facility to store your belongings, try to leave any valuables at home.

You should also avoid wearing metal of any sort. While the focus of the scan will be on the breasts, your entire body will go inside the tube. As such, you will need to take care not to bring the following into the MRI room:

  • Jewelry
  • Watches
  • Hearing aids
  • Hairpins
  • Zippered pants
  • Dentures
  • Body piercings
  • Cell phones
  • Credit cards (which can demagnetize)

If at all possible, leave these items at home.

Food and Drink

There are no food and drink restrictions prior to an MRI procedure. You can eat and drink as you normally would. You can also take your daily chronic medication as usual.

Cost and Health Insurance

MRIs tend to be costly but can vary in price from one facility to the next. If you are paying out of pocket, shop around for the best price. If you have insurance, check to ensure that the facility is an in-network provider. Out-of-network providers almost invariably cost more.

Hospitals tend to charge more than imaging centers but often have newer-generation equipment, including rapid abbreviated breast MRI (AB-MRI) units. Depending on where the test is being done, the cost can run anywhere from $700 to $4,000. If you have to pay out of pocket, ask the facility if they offer a monthly payment plan or an upfront discount payment.

Be aware that may need to get prior authorization from your insurer before undergoing a breast MRI. Your doctor can usually help you with this. If you fail to do so, your insurer could very well deny the claim.

Due to their high cost, AB-MRI tests are rarely covered by insurance.

What to Bring

You will need to bring your ID and insurance card with you, particularly if it's the first time you've been to the facility. If you intend to use a mild sedative, bring someone along who can drive you home after the MRI.

During the Test

For this test, you will be working with an MRI technologist who will perform the scan and provide you instruction. There may also be a nurse on hand to assist.

Pre-Test

Upon arrival, you will be provided both a consent form and a medical history questionnaire. If you plan to take a mild sedative, now would be the time to do so. It generally takes between 20 and 40 minutes to feel the sedative effect.

Once the documents have been completed, you would be led to a changing room and asked to remove all of your clothing from the waist up. A hospital gown would be provided. Remove any and all removable metal objects.

You would then be led to an examining room where the technologist or nurse would review your medical history and check your heart rate, temperature, and blood pressure. Close attention would be paid to any allergies or implanted devices you have. If you are prone to claustrophobia or have taken a sedative, now would be the time to let the medical staff know.

A tourniquet would then be placed on your arm, and an intervenous (IV) line would be inserted into either your arm or hand. You would then be led to the MRI room for the test.

Throughout the Test

The breast MRI machine consists of a table which glides in and out of a tube-like chamber. The table is specially equipped with hollow depressions through which your breasts would be inserted while you are lying face-down. Inside the depressions are donut-shaped coils which act as signal receivers for the imaging process. There will also be a padded face cradle, similar to the hole in a massage table, where your face would be placed.

Upon arrival, you would be seated on the MRI table. A normal saline solution with heparin, an anticoagulant, would be instilled through the intravenous line to prevent clotting. The gadolinium agent would then be administered, the metal particles of which respond to the magnetic waves to help differentiate tissue density.

You would then be placed face-down on the table with your breasts inserted into the hollow depressions. You would need to rest your arms above your head with your face in the padded cradle.

The technologist would then slide your body remotely into the MRI tube, communicating via the two-way speaker. As images are captured, the unit will make loud thumping and whirring noises as the magnet switches on and off. Some facilities will provide you with headphones to help block out the noise.

You will need to stay very still while the scans are being performed, each of which takes a few minutes to complete. Tell the technologist if you need to move or take a break.

Post-Test

Once the test is complete, you would be asked to wait until the technologist confirms that all of the images are clear and readable. If required, you may be asked to repeat certain images. Once those are okayed and the IV line is removed, you can return to the dressing room to change.

Unless you have taken a sedative, you can leave once you are dressed. Some facilities may ask you to sign out. If you have taken a sedative, do not drive yourself home. Either organize a taxi or have a friend take you there and back.

After the Test

Generally speaking, there are no after-effects to a breast MRI procedure. You may have pain, redness, or bruising at the IV injection site. On rare occasion, you may experience an allergic reaction to the gadolinium solution. Most cases are mild.

Call 911 or seek urgent care if you experience widespread rash or hives, shortness of breath, wheezing, high fever, irregular heartbeats, dizziness, or the swelling of the face, tongue, or throat after undergoing a gadolinium-enhanced MRI.

Although anaphylactic reactions to gadolinium are rare (occurring in 0.0003 percent of cases, according to a 2016 study from Italy), they can be life-threatening unless treated immediately.

If you were given gadolinium and are nursing, some doctors will tell you to wait 24 hours before breastfeeding. For its part, ACOG insists that there is no need to interrupt breastfeeding after a gadolinium infusion.

Interpreting Results

Once the MRI images are approved by the technologist, they are sent to a radiologist for review and interpretation. A copy of the scans along with the radiologist's report will be sent to your physician, usually within one to two working days.

A typical radiology report will include a detailed list of scans along with a classification of findings (usually normal, abnormal, or potentially abnormal). The radiologist will also provide an interpretation of the findings and the likely diagnoses. If the results are inconclusive, the report may include other possible causes to explore (referred to as the differential diagnoses).

Follow-Up

An MRI can provide strong evidence of a condition, such as cancer, but cannot usually provide a definitive diagnosis on its own. When diagnosing breast cancer in particular, only a biopsy can do that.

If used for cancer staging, pre-surgical assessment, or post-treatment evaluation, an MRI can provide valuable information to help direct medical care.

If a finding is abnormal, potentially abnormal, or inconclusive, your doctor may recommend additional tests to either reach a definitive diagnosis or explore the extent of malignancy. These may include:

For screening purposes, a breast MRI may be performed annually alongside a mammogram if you are at increased risk of cancer.

If you're unsure whether you are at high risk of breast cancer, ask your doctor to conduct a personal risk assessment or refer you to a breast health specialist who can.

A Word From Verywell

However safe it may be, a breast MRI can distress and anxiety. In most cases, it will only be ordered if there is a cause for concern. This shouldn't suggest that having a breast MRI means that you have cancer or will likely get cancer. It is simply one of many tools used when other tests cannot provide enough information.

Although there have been suggestions that abbreviated (fast) MRI systems will one day replace mammograms, until prices come down and false-positive rates improve, that is unlikely to happen, say researchers from the NYU School of Medicine.

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