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Molecular Breast Imaging

Molecular breast imaging (MBI) is an imaging exam performed as an additional improved test to mammography for detecting cancer within the breasts.

MBI uses a radiotracer called Technetium-99m-Sestamibi (also known as Miraluma) that is injected into the bloodstream and accumulates in cancer. During the imaging portion of the exam, the breast is placed between two cameras that visualize the areas in the breast where the radiotracer accumulates. Images obtained using the MBI imaging system can reveal abnormal areas in the breast where the radiotracer has localized since cancers accumulate more of this radiotracer compared to normal breast tissue. Compared to mammography, the MBI camera uses only mild compression to immobilize the breast.

MBI can help detect breast cancer in women with dense breasts. Up to half of all women have dense breast tissue. When a breast is dense, a cancer sometimes can be hidden by the surrounding normal breast tissue (Figure 1). This lowers the sensitivity of the mammogram as a test for breast cancer detection compared to women without dense breast tissue. MBI is not affected by dense breast tissue and can reveal breast cancers in women with dense breast tissue that mammography cannot (Figure 2).

Figure 1:

Illustration of how a cancer may be difficult to identify on a mammogram for women with dense breast tissue.

Image created by and used with permission from Matt Covington, MD.

Figure 2:

Right breast invasive ductal cancer is invisible on the mammogram (left panel images - A), however is clearly seen with MBI (middle panel images - B) as well as with breast MRI (right panel images - C, D).

A, Right breast screening mammogram showed dense breast tissue and was interpreted as a negative mammogram.

B, MBI showed a large (3 cm) mass in the right breast (arrows) and normal left breast.

C, D Breast MRI showed large mass in the right breast (arrows), corresponding to the mass seen at the MBI, and normal left breast (D).

Image contributed by Gaiane M. Rauch, MD, PhD, UT MDACC.

MBI can also be useful for evaluating inconclusive findings on mammography or as an alternative to breast MRI in women who cannot complete MRI due to claustrophobia or other factors. For patients already diagnosed with breast cancer, MBI can evaluate whether breast cancers respond to therapy before surgery.

Another type of breast cancer imaging test that uses Technetium-99m-Sestamibi is called Breast Specific Gamma Imaging (BSGI). BSGI has been used for the same indications as MBI with similar advantages of increased breast cancer detection in addition to mammography. Compared to MBI, BSGI uses one camera with less sensitive detector technology and requires a higher radiotracer dose. At present, MBI is the preferred imaging system over BSGI among the available breast specific cameras.

MBI advantages and disadvantages


  • Identify some breast cancers not detected by mammography
  • Identify more breast cancers in women with dense breast tissue than mammography, digital breast tomosynthesis (“3D mammography”), and ultrasound
  • Provide information that helps physicians and patients choose the most appropriate treatment plan
  • Can be used for tissue biopsy of suspicious findings identified on MBI for diagnosis


  • Not widely available in medical centers around the USA.
    Visit this link for a listing of U.S. MBI Centers.
  • Exam takes 30-45 min
  • Radiation exposure is currently slightly higher than mammography, but much less than other imaging tests like CT and PET scans

 MBI is useful for women:

  • with dense breast tissue
  • with newly diagnosed breast cancer to evaluate amount of disease in the breast
  • with breast cancer receiving chemotherapy, to check for response to the treatment
  • with inconclusive or unclear findings on mammogram or ultrasound
  • who cannot tolerate breast MRI
  • with breast implants when mammograms are limited

Where can I learn more?

MBI is available at select medical centers in the United States. Ask your primary care practitioner about MBI in your community.  If your provider is unsure about the status of MBI cameras in your community, please encourage your provider to discuss MBI with a local nuclear medicine physician or radiologist to learn more.

MBI is FDA approved; however insurance coverage may vary.  Ask your specific insurance carrier regarding coverage.


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