Molecular Breast Imaging: A Better Way to Spot Tumors in Dense Tissue

Tuesday, March 10, 2009

ROCHESTER, Minn. — Molecular breast imaging (MBI), a new screening method for breast cancer, identifies tumors in dense tissue that often aren't visible with mammography. In the March issue of Mayo Clinic Women's HealthSource, Deborah Rhodes, M.D., a Mayo Clinic researcher who helped develop the technology, discusses why MBI may eventually serve as an adjunct to mammography.

MBI overcomes a shortcoming of mammography, which is taken with X-rays. The X-ray imagery doesn't differentiate between tumors and dense breast tissue. On a mammogram, they both appear white.

"With MBI, a tumor is easy to see, even if it's in dense breast tissue," says Dr. Rhodes.

Here's why: With MBI, a woman is given an injection of a short-lived radioactive agent. This material accumulates in tumor cells more than it does in normal cells. Using a radiation-detecting camera, tumors show up as hot spots on the resulting image.

In a recent Mayo Clinic study comparing MBI with mammography, MBI detected three times as many cancers in women with dense breast tissue and an increased risk of breast cancer. Another advantage over mammography: MBI also demonstrated fewer false positives, meaning the results appear abnormal but are noncancerous.

For now, MBI use is limited to research. The focus is to reduce the dose of radiation needed to perform MBI. The risk from the radiation dose of one or two MBI scans is extremely low. But to safely use MBI annually or every few years, the radiation dose needs to be reduced.

"Our goal is to have a dose that's no higher than that from a routine mammogram," says Dr. Rhodes. "If we get results that are similar to, or better than, our last study, we'll be well on our way to supporting MBI as an option for women with dense breast tissue."

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