Molecular Breast Imaging Test
Overview
Molecular breast imaging (MBI) is a specialized technique for detecting signs of breast cancer, especially in those with dense breast tissue. During the procedure, a healthcare provider injects a small amount of radioactive tracer into a vein. The tracer travels through the bloodstream and collects in breast cells. Rapidly dividing cells, such as cancer cells, absorb more tracer, which makes them stand out during imaging.
A gamma camera scans the breasts and captures images, highlighting areas with increased tracer uptake. The most active cells appear brighter, making it easier to spot potential problems. MBI provides functional imaging, focusing on cell activity rather than just structure. Other advanced imaging tests include CEM, EIT, PEM, and techniques like BSGI, scintimammography, and positron emission mammography.
| Imaging Technique | Highlights |
|---|---|
| MBI (Molecular Breast Imaging) | Useful for dense breasts |
| PEM (Positron Emission Mammography) | High spatial resolution |
| BSGI (Breast-Specific Gamma Imaging) | Good for functional imaging |
Reasons for Molecular Breast Imaging
Molecular breast imaging (MBI) is used when traditional screening tools, like mammograms, may not provide clear results—especially for individuals with dense breast tissue. In dense breasts, both tissue and tumors can appear white on standard mammograms, making it harder to spot abnormalities. MBI highlights cell activity, offering a different way to detect cancer.
This imaging test is often recommended when other tests are inconclusive or when added detail is needed to plan next steps. It can be helpful for investigating suspicious areas, evaluating the size or spread of a known tumor, or guiding a biopsy. MBI may also be used in women at higher-than-average risk of breast cancer who cannot undergo MRI, or as a supplemental tool for screening alongside mammography.
When MBI May Be Recommended
- Mammogram results are unclear or show questionable areas.
- Dense breast tissue makes mammograms harder to interpret.
- A previous cancer diagnosis requires further evaluation.
- There’s a family history or increased genetic risk, and MRI is not an option.
- Additional imaging is needed before a biopsy or surgery.
In these situations, MBI provides functional insights that complement anatomical views from other imaging tests. By showing how cells behave, it can reveal abnormalities that may not yet cause physical changes.
Possible Concerns
Molecular breast imaging uses a small amount of radioactive material called a tracer. The tracer releases a low dose of radiation. Most experts agree that the amount of radiation is low enough to be safe for standard screening. Some individuals may react to the tracer. Allergic reactions rarely occur, but people should inform a healthcare provider about any known allergies before the test.
Other possible concerns include false positives. Sometimes, the scan shows a result that is not cancer. This can lead to more tests, which may be stressful or inconvenient. False negatives can also happen. The imaging might miss cancers, especially if the tumors are in hard-to-see locations.
| Possible Risk | Explanation |
|---|---|
| Radiation Exposure | Very low; considered safe for most people. |
| Allergic Reaction | Rare; inform provider about allergies. |
| False-Positive Result | May require more tests, but do not always mean cancer. |
| Missed Cancers | Tumors in some areas might not be detected. |
What to Do Before a Molecular Breast Imaging Test
Before having a molecular breast imaging test, patients should follow these important steps:
- Insurance Check: Contact your insurance provider to make sure the test is covered.
- Pregnancy & Nursing: Tell the healthcare provider if you are pregnant or nursing. Since molecular breast imaging uses a radioactive tracer, health professionals do not recommend it during pregnancy. For nursing mothers, they may recommend pausing breastfeeding for a short time so the radiopharmaceuticals, such as Tc-99m sestamibi or Tc-99m tetrofosmin, can clear from the body. Pumping and storing milk before the test is also an option.
- Timed Scheduling: People who have menstrual cycles are encouraged to schedule the test within days 3 to 14 after their period starts.
Table: Key Preparation Points
| Preparation Step | Details |
|---|---|
| Insurance Verification | Confirm coverage with insurance provider. |
| Pregnancy Check | Notify if pregnant; test is not recommended. |
| Breastfeeding | Pause nursing as advised; consider storing pumped milk. |
| Menstrual Cycle | Schedule between day 3-14 of cycle, if possible. |
| IV Placement | A provider will place an IV before injecting the radioactive tracer. |
Staying hydrated with clear liquids can also help, but patients should avoid eating before the test unless told otherwise.
What You Might Experience
Steps Involved in the Test
At the start of the molecular breast imaging exam, the patient changes out of their clothes above the waist and puts on a gown. A provider may offer a blanket for comfort and to help the process go smoothly, as warmth can help with the test. Next, a healthcare professional injects a small amount of radioactive tracer into a vein in the arm.
The tracer is drawn to cells that grow more quickly, such as cancer cells, making them easier to detect. The patient then sits in front of the imaging equipment, which uses two small gamma cameras. These cameras can help spot changes that are not always seen on standard mammograms or digital mammography, especially for those with dense breast tissue.
The provider places one breast at a time between the cameras, which give a gentle but firm compression. The compression is much lighter than what most people experience with 2D mammography, 3D mammography, or breast tomosynthesis. The person stays still for about 10 minutes while each image is made. This is done for both breasts, unless imaging is only needed on one side.
Key Points
- The patient is seated, not standing.
- Two images per breast are made.
- Soft pillows or supports may be used for comfort and to keep the body steady.
This method uses gamma rays—unlike ultrasound, breast MRI, or PET scans—and providers often choose it when other tests, such as mammograms or tomosynthesis, give unclear results. It can be especially useful before a breast biopsy or when checking the biopsy capability of a suspected area.
What Happens Afterwards
Once the imaging is complete, the patient can get dressed. There is no waiting period before returning to normal routines. The radioactive tracer leaves the body naturally over time. A radiologist will review the images, sometimes comparing them with previous mammograms, breast ultrasound scans, or results from contrast-enhanced mammography. The provider will let the patient know about the findings, often within a week.
Test Outcomes
After molecular breast imaging, a radiologist examines the images closely to identify any abnormalities. Cancer cells usually absorb more of the radioactive tracer, which creates bright spots on the final images. These spots can indicate invasive breast cancer or other types of breast lesions.
Detection Features
- Highly sensitive for finding cancer, especially in dense breast tissue.
- Can help identify the extent of disease.
- Highlights both invasive ductal cancer and smaller abnormalities.
| Aspect | Finding |
|---|---|
| Cancer detection | Bright spots on scan |
| Sensitivity | Often increased |
| Specificity | Varied, risk of false positive result |
| False positives | Possible, may require more tests |
If cancer is suspected, doctors may order more imaging or a biopsy.
