What Is Molecular Breast Imaging?

What to expect when undergoing this test

Many women are familiar with a standard mammogram performed as part of an annual, routine women’s health exam. But recent developments in the field of breast imaging 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 with dense breast tissue.

MBI is done using a unique gamma camera and a radioactive tracer to target cancer in a specific area of the body; in this case, it’s breast tissue. Instead of taking a single picture of the breast tissue, MBI technology can show changes in the tissue, a process known as functional imaging. 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, MBI detected four times the incidences of invasive breast cancer per 1,000 women, according to a study in Breast Cancer Management. The rate of breast cancer detection in women who have dense breast tissue using mammography alone is about 3 in 1,000 women. Whereas, with the addition of MBI, the rate increases to 12 out 1,000 women.  

For women with dense breast tissue, MBI offers a promising, complementary way to screen for the presence of breast cancer.

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

Purpose of Test

Although MBI shows potential, it’s considered a new technology, so it’s not widely available yet. MBI may be useful in the following cases.

When there’s a need for additional testing measures in women with dense breast tissue

The Breast Cancer Management study notes that mammography tends to “underperform” in women with dense breast tissue. Early breast cancer detection is paramount to increase a woman’s chance of survival. For early detection to occur, technology needs to be able to locate small cancers so that they can be treated in a more timely manner. Currently, MBI is improving tumor detection rates among women with dense breast tissue when used as an adjunct to mammograms.

When the doctor needs to take a closer look at breast abnormalities  

If a lump or an area of concern is detected during a mammogram, your doctor may consider MBI to verify the findings. Additionally, your doctor may choose MBI if other tests have been unsuccessful at providing answers or if you’re allergic to dyes used in other imaging procedures like magnetic resonance imaging (MRI).

Risks and Contraindications

MBI is considered a safe testing method, but there are some risks to consider when determining if it’s the right course of action for you.

  • You are exposed to low levels of radiation, especially when the test is combined with a mammogram. But a review in the American Journal of Roentgenology states that the radiation dose from the combined tests is still considered an acceptable dose. For many women, there’s more of an upside to having the test than a downside.
  • 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.
  • MBI can cause false-positive findings, where an area of concern may look like cancer, but it turns out not to be. A worry of this kind can take a mental and emotional toll on you, particularly if your doctor recommends additional testing to assess the area.
  • No testing measure is one hundred percent foolproof, which means it may miss some cancers. Your doctor can discuss other measures that can be taken for screening.

Also 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 nursing, your doctor may want you to wait a certain amount of time before you resume nursing so that your body has time to remove the tracer.

Before the Test

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


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, putting on a gown, and getting dressed 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 tracers 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 instruction before your appointment.

Cost and Health Insurance

Before undergoing the BMI, 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 could help you gain pre-approval.

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. But in general, you can expect the following to occur:

  • You’ll be asked to undress from the waist up and be given a gown to wear until the test begins.
  • 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 like in a mammogram, you’ll 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 you feel pain. The test should not cause pain.
  • You’ll remain in one position for about 10 minutes while the cameras record the activity that’s happening in the 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 it’s okay for you to 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. There are no side effects to manage once you are done.

    Interpreting Results

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

    Your doctor or a member of their staff will 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.

    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 can be very scary. Molecular breast imaging provides healthcare providers with another tool for early detection of tumors in women with dense breast tissue, which increases the rates of obtaining treatment sooner, surviving breast cancer, and thriving again.

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    Article Sources
    • Breast360.org. Molecular Breast Imaging.
    • 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.
    • 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.