What Is Molecular Breast Imaging?

What to expect when undergoing this test

In This Article

You're probably familiar with the standard mammogram that's part of a routine annual women’s health exam. Recent developments in the field of breast imaging, however, demonstrate that using a procedure known as molecular breast imaging (MBI) may be a game-changer when it comes to detecting breast cancer in women who have dense breast tissue.

MBI uses a unique gamma camera and a radioactive tracer to target cancer in a specific area of the body. Instead of taking a single picture of your breast tissue, MBI technology is known as "functional imaging" because it can show what's going on in the tissue. For example, breast tissue that consists of cells that quickly grow and divide, like cancer cells, will show up brighter in an image compared to the tissues where the cells are less active.

When used in conjunction with mammography, molecular breast imaging detected breast cancer in dense tissues at nearly quadruple the rate of mammography alone, according to a study in Breast Cancer Management. The earlier breast cancer is caught and treated, the better the outcome is likely to be, so this is an important step forward for a lot of women.

what to expect during a molecular breast imaging test
Illustration by Cindy Chung, Verywell

Purpose of Test

Although MBI shows potential, it’s considered new technology, so it’s not yet widely available. That may change as more doctors become aware of MBI and if it continues to show effectiveness in studies.

The aforementioned Breast Cancer Management study notes that mammography tends to “underperform” in women with dense breast tissue. Early detection is paramount for increasing the chance of survival. But in order for this to occur, technology needs to be able to locate small cancers so they can be treated right away.

Currently, molecular breast imaging is improving tumor detection rates among women with dense breast tissue when used as an adjunct to mammograms.

Dense breasts are more common among premenopausal women and postmenopausal women on hormone therapy. Dense tissue shows up white on a mammogram, but so does cancer. That makes it hard to see on a mammogram, which can delay a cancer diagnosis.

The only way to know if you have dense breasts is by having a mammogram. You can't tell by the look or feel of them.

If a lump or an area of concern is detected during a mammogram, your doctor may consider MBI to verify the findings even if you don't have dense breast tissue. Additionally, your doctor may choose MBI if other tests have been inconclusive or if you’re allergic to dyes used in other imaging procedures, such as magnetic resonance imaging (MRI).

Risks and Contraindications

MBI is considered a safe testing method, but you do have some risks to consider when determining whether it's right for you.

  • Radiation: You are exposed to low levels of radiation, especially when the test is combined with a mammogram. However, a review in the American Journal of Roentgenology states that the radiation dose from the combined tests is still considered acceptable. For many women, there’s more of an upside to having the test than a downside.
  • Allergies: While not common, it’s possible to have an allergic reaction to the tracer used in the test. Your medical team will be prepared to handle this situation if it arises.

Be sure to tell your doctor if you’re pregnant or nursing. Because the test emits a low-dose of radiation, the test is not advised if you’re pregnant. If you’re breastfeeding, your doctor may want you to take a break to allow your body time to remove the tracer.

Before the Test

Knowing these things may help ease your mind and prepare for the test.

Timing

You may need to reserve an hour or more for the test. The test itself takes about 40 minutes, but you’ll need to allow for potential time in the waiting room, undressing, and getting dressed again after the test.

What to Wear

You can wear your normal clothes to the appointment, but you’ll be asked to undress from the waist up and put on a gown.

Food and Drink

You’ll probably be asked to fast before the test, as fasting increases the tracer's ability to reach breast tissue and optimize the pictures. Most likely, you’ll be allowed to drink liquids, but there may be some restrictions on the types of beverages you’re able to have. You should be given specific instructions before your appointment. If you're not sure, ask.

Cost and Health Insurance

Before undergoing molecular breast imaging, review your benefits with your insurance company. Since MBI is a relatively recent development in the imaging world, it may not be covered by all insurance plans, or it may require pre-approval. Your doctor's office should be able to help you gain pre-approval.

Your doctor's office and the facility performing the test should be able to answer questions about what it will cost if you don't have insurance, as well.

What to Bring

On the day of your appointment, bring your insurance card with you, a form of identification, and any paperwork you were asked to fill out.

During the Test

The facility or clinic where you have the test will provide you with details of the procedure, which will be performed by an imaging technician. In general, though, you can expect the following to occur:

  • Your arm will be injected with the radioactive tracer, which is quickly absorbed by cells that may be rapidly growing in your breast tissue.
  • Typically, you’ll sit, and, as with a mammogram, place your breast on the flat surface of the bottom camera. Then the flat surface of the raised camera will be lowered on top of your breast. You’ll feel a slight compression as the two surfaces hold your breast in place.
  • Be sure to let the technician or doctor know if you’re uncomfortable or in pain. The test should not hurt.
  • You’ll remain in one position for about 10 minutes while the cameras record activity in your breast tissue.
  • After one image is created, your breast will be repositioned, and you’ll sit for another 10 minutes.
  • If both breasts are being evaluated, you’ll repeat the process on the other side.
  • The technician will let you know when the test is finished and when you can leave.

After the Test

If you’re nursing, you may be given specific follow-up instructions. Otherwise, once the test is finished, you’ll be able to get dressed, head out, and restart your regular activities. You shouldn't have any side effects afterward.

Interpreting Results

Test results are typically not ready right away since a radiologist has to review the images and submit a summary report to your doctor. They are looking for bright areas where the tracer was taken up by cells, which could suggest cancer.

Your doctor's office should contact you to discuss the findings. At this time, you’ll also be notified if you need to make an additional appointment or if you’ll require further testing.

No testing measure is 100% foolproof, which means molecular breast imaging may miss some cancers. (Your doctor can discuss other measures that can be taken for screening.)

In addition, MBI can cause false-positive findings, where an area of concern may look like cancer, but it turns out not to be. That can take a mental and emotional toll on you, particularly if your doctor recommends additional testing to assess the area.

Molecular breast imaging results can very useful, but it's important to be aware of these possibilities.

You can always ask for a copy of both the original images (likely delivered via disc) and a copy of your report in case you'd like a second opinion.

A Word From Verywell

Hearing the word cancer is scary. Remember that technology is giving doctors the ability to diagnose breast cancer earlier, and that gives you a much better outlook. Molecular breast imaging gives healthcare providers another tool for early detection, which increases the chance of early treatment, surviving breast cancer, and thriving again.

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Article Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. O’Connor MK. Molecular breast imaging: an emerging modality for breast cancer screening. Breast Cancer Management. 2015 Jan 1; 4(1): 33–40. doi:10.2217/BMT.14.49

  2. National Cancer Institute. Dense breasts: Answers to commonly asked questions; 2018.

  3. Shermis RB, Wilson KD, Doyle MT. Supplemental breast cancer screening with molecular breast imaging for women with dense breast tissue. American Journal of Roentgenology. 2016;207:450-457. doi:10.2214/AJR.15.15924

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