What is digital breast tomosynthesis (DBT)?

Updated: Oct 17, 2016
  • Author: Nagwa Dongola, MD, FRCR; Chief Editor: Peter Eby, MD  more...
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Answer

Digital breast tomosynthesis (DBT), also known as 3D mammography, uses the same compression and views as 2D mammography and adds a 3D volume acquisition. The examination requires only a few additional seconds for each view, and most women will not be able to tell the difference between having a 2D or 3D exam. A traditional 2D exam displays the entire volume of the breast on a single 2D image. When viewed in this manner, the normal dense parenchyma can cause some normal tissue to look like possible cancer and can also hide cancers. DBT addresses some of these challenges of 2D mammography.

The 3D volume of the entire DBT acquisition can be displayed on a monitor and viewed as slices as thin as 1 mm. This ability theoretically allows the radiologist to see cancers that might be obscured, improving sensitivity. It should also allow the radiologist to separate normal tissue and avoid an unnecessary recall, improving specificity. The research has confirmed the improved performance of this test. In a multicenter reader study published in 2013, the sensitivity and specificity for breast cancer was found to be significantly better with DBT than with 2D digital mammography. [11]

In a reader study with an enriched population, 2-view tomosynthesis outperformed standard 2D mammography in terms of accuracy, as measured by the area under the ROC curve, for both masses and microcalcifications. [12]

Skaane and colleagues concluded that the combination of tomosynthesis and digital mammography resulted in a significantly higher cancer detection rate (27%, P =.001) and reduction in false-positive findings (15%, P< .001), as compared with digital mammography alone (N = 12,621). [13]

In one study, the addition of 2-view tomosynthesis to conventional digital mammography during screening examinations resulted in a 29.7% decrease in recall rates (P< .01; N = 13,158). The greatest reduction in recall rates occurred in patients with dense breasts and in those younger than 50 years. [14]

Feng and colleagues demonstrated that DBT, on average, delivers twice the radiation dose to the breast than 2D digital mammography. [15] This isn’t surprising, since the DBT examination begins with the 4 standard views of 2D screening mammography, followed by 4 tomosynthesis views. However, the dose remains below the limit set by the FDA for screening mammography. In addition, Hologic has developed a software-based reconstruction algorithm that transforms the DBT images into a 2D image. If approved and instituted, the dose for a DBT exam would be the same as that for a 2D exam, with higher sensitivity and specificity.

DBT was approved by the FDA in 2011. Many centers across the United States and Europe are replacing their 2D mammography machines with DBT because of the increased sensitivity and specificity, although there are no data regarding a mortality benefit. Regarding DBT, the ACR has stated that “breast tomosynthesis has shown to be an advance over digital mammography, with higher cancer detection rates and fewer patient recalls for additional testing.” [16]


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