SAN ANTONIO—Digital tomosynthesis appears to be more sensitive than digital mammography for detecting breast cancer in a clinical setting, Debra M. Ikeda, MD, of Stanford University, reported at the 2007 San Antonio Breast Cancer Symposium (abstract 46).
“Tomosynthesis is extremely exciting technology that is fast, reproducible and inexpensive,” Dr. Ikeda said.
As background, Dr. Ikeda noted that up to 30% of breast cancers are missed with film mammography screening, often because of “anatomic noise” (seen with dense breast tissue), lack of contrast (no attenuation difference), or a tumor growth pattern that shows a lack of tumor bulk or lack of edge characteristics. These problems are not corrected by the use of digital mammography.
“We expected digital mammography to be better,” she noted. “But foreground and background breast tissue can still hide the cancer.” Tomosynthesis can reduce this anatomic noise, she said.
Tomosynthesis is a technological outgrowth of digital mammography but offers a three-dimensional view of the breast’s inner structure: film screen mammography artificially flattens such features into two dimensions.
“Consider it like a chest CT compared to a chest x-ray,” Dr. Ikeda said. “With tomosynthesis, you roll through the image, moving back and forth throughout the breast like a CT scan. This gives the radiologist a longer time in which to visualize a mass. ”
Tomosynthesis integrates up to 25 radiographic exposures per breast, each taken from a different vantage point along an arc. The multiple perspectives yield a 3D image of the breast in which tiny virtual slices can be individually examined.
The radiation dose from tomosynthesis is equal to or less than that of a standard two-view mammogram, and less compression of the breast is required during the 20 seconds of data acquisition.
In conjunction with researchers from Lund University, Malmö, Sweden, Dr. Ikeda conducted a comparative study in a clinical setting that involved 29 patients with subtle signs of breast cancer detected through digital mammographic or clinical screening.
Tomosynthesis was performed on a prototype machine, adapted from the digital Mammomat Novation (Siemens), in the projection in which the finding from mammography was least visible or not visible.
Tomosynthesis results were reviewed for signs of breast cancer by two expert breast radiologists (unblinded), who classified the findings for lesion visibility and probability of cancer using BIRADS categories.
In addition to digital mammography and tomosynthesis, patients underwent ultrasound evaluation and needle biopsy followed by surgery.