Molecular breast imaging is a diagnostic tool used to detect breast cancer. It is a type of functional imaging, which means it provides information about the activity within the breast tissue rather than just its structure. Unlike mammograms that show anatomy, MBI focuses on cellular function to highlight potentially abnormal areas. This allows healthcare providers to gather more detailed information about areas that may require further investigation.
How Molecular Breast Imaging Works
Molecular breast imaging (MBI) uses a radiotracer and a specialized gamma camera. The procedure begins with an injection of a small amount of a radioactive tracer into a vein, which is absorbed by cells throughout the body.
Cancer cells have a higher metabolic rate than healthy cells, causing them to absorb the radiotracer more readily and in greater quantities. This process creates areas of higher radioactive concentration within the breast.
The specialized gamma camera detects the gamma rays emitted by the tracer. As the camera scans the breast, it pinpoints these “hot spots” of increased radiotracer uptake, which appear as bright areas on the resulting images. This allows radiologists to see functional differences between healthy and potentially cancerous tissue.
Candidates for Molecular Breast Imaging
MBI is used as a supplemental screening tool and is valuable for individuals with dense breast tissue. On a standard mammogram, both dense tissue and tumors appear white, making them difficult to distinguish. MBI overcomes this limitation by highlighting metabolic activity, causing tumors to appear bright while the dense tissue remains dark.
This imaging method is also used when results from a mammogram or ultrasound are inconclusive, as it can provide functional information to clarify the findings. It serves as an alternative for patients who need detailed imaging but cannot undergo a breast MRI due to a pacemaker or other implanted device.
The Patient Experience
Before the scan, the patient receives an injection of the radiotracer into a vein. After about five minutes, the tracer is absorbed by the breast tissue, and imaging can begin. Patients may be advised to avoid food for a few hours beforehand to help the tissue absorb the tracer more effectively.
During the imaging process, the patient is seated while one breast at a time is placed between two small gamma cameras. Light compression is applied to hold the breast stable, which is less intense than the compression during a mammogram. Each view lasts about seven to ten minutes, and the entire procedure takes around 40 to 45 minutes.
After the scan, there are no restrictions on activity. The radiotracer is naturally eliminated from the body within 48 hours, primarily through urine. Drinking extra water can help flush the tracer out more quickly.
Interpreting the Results
A radiologist interprets MBI scans by looking for areas where the radiotracer has accumulated more intensely, suggesting heightened metabolic activity and a potential tumor.
The results are categorized to reflect the level of concern. A negative result means no abnormal uptake was detected. A suspicious area does not automatically mean cancer is present, as some benign conditions can also cause increased uptake.
If a suspicious finding is reported, the next step is often a biopsy. This procedure involves taking a small tissue sample from the area of concern for laboratory analysis to determine if cancer cells are present.