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Tech Report: The Gamma Camera
By Janet Mandelstam
A 2005 biopsy confirmed that the palpable lump in Nancy Upton’s left breast was cancerous, and she scheduled surgery. Then, she recalls, her doctor asked, “What about the right breast?” Upton, 53, had had a clear mammogram just six months before finding the lump during a self-exam. But because she has dense breasts, Sheldon Feldman, M.D., chief of the Appel-Venet Comprehensive Breast Service at New York’s Beth Israel Medical Center, wanted to be sure that nothing else had been missed.
He prescribed what was then a relatively new test, Breast-Specific Gamma Imaging (BSGI), which can help identify cancer in women whose mammograms are inconclusive or difficult to read.
Here’s how it works: The patient is injected with a small amount of tracing agent that is quickly taken up in metabolically active cells. Then a trained technologist uses a special gamma camera, the Dilon 6800, to scan the breast. The tracer emits invisible gamma rays, which the camera picks up and translates into a digital image of the breast. If cancer cells are present, more of the tracer will collect in those cells than in normal cells; those “hot spots” appear as dark areas in the image. The high-resolution camera can detect cancers as small as three millimeters. And because BSGI provides the same views as mammography, it is easy to compare the two images. In addition to detecting tumors, the camera can rule out cancer in suspicious-looking areas.
Nancy Upton’s scan changed her treatment plans and her life. “It found a small, young cancer in the other breast just days before my surgery,” she says. With that knowledge, her doctors performed lumpectomies on both breasts.
Feldman prescribes BSGI as a follow-up for high-risk patients with previous breast cancers, family history of the disease, dense breast tissue, implants or scarring from previous surgery. However, he stresses, mammography and self-exams are still the primary cancer detection tools.
At the Solis Bertrand Breast Center in Greensboro, North Carolina, Margaret Bertrand, M.D., prescribes BSGI for symptomatic patients whose mammograms “are not straightforward.” She says that in some 10 percent of cases, the results dictate a change in surgery from a lumpectomy to a mastectomy.
BSGI differs from MRI screening in that it detects more cellular activity. According to Robert Moussa, president and CEO of Dilon Technologies, the BSGI camera is being integrated into comprehensive breast centers around the country.
