Breast imaging technique zeros in on subcentimeter lesions

A new gamma camera developed by researchers at the Mayo Clinic in Rochester, MN, is being used in what's touted as a molecular breast imaging technique.

Unlike conventional scintimammography, which uses sodium iodide crystals, the Mayo camera uses a cadmium-zinc-telluride semiconductor detector. The detector can be placed very close to the breast, eliminating the dead space associated with conventional scintimammography.

This close positioning provides much better resolution, improving the ability to detect small lesions, said Dr. Deborah J. Rhodes, director of the women's executive health program at Mayo.

Rhodes and colleagues mounted the gamma camera, with a field-of-view of 20 x 20 cm and detector elements of 2.5 x 2.5 mm, onto a modified mammographic gantry. Between November 2001 and March 2004, they imaged 40 women who were scheduled to undergo biopsy. The study was published in the January issue of the Mayo Clinic Proceedings.

Using 20 mCi of technetium-99m sestamibi, they obtained craniocaudal and mediolateral oblique views of both breasts.

The imaging technique detected 33 of 36 lesions confirmed to be malignant by surgery, for an overall sensitivity of 92%. It detected 19 of 22 surgery-confirmed lesions smaller than 1 cm, for a sensitivity of 86%.

Because molecular breast imaging is not influenced by breast density and is much less costly than MRI, the technique may be more appropriate than MRI as a screening tool in high-risk women, Rhodes said.

"We feel this type of imaging fills a critical gap in breast imaging options. It will not replace mammograms, ultrasound, or MRI but will offer an important additional option to subgroups of women not served well by traditional imaging techniques, such as women with dense breast tissue, women with prior surgery or radiation of the breast, and many other potential groups," she said.

For more information from the Diagnostic Imaging archives:

Technique adds dimension to nuclear mammography

Breast MR builds its role among high-risk patients

Radiology's role grows in biopsy decisions, procedures

New PET scanners take aim at breast cancer detection