Digital breast tomosynthesis: The next generation of advanced mammography

Digital breast tomosynthesis (DBT) is a burgeoning modality that offers many advantages over basic digital mammography, including improved recall rates, workflow, and a wide range of uses both inside and outside of mammography. While there are minor drawbacks with DBT, radiology departments would benefit from increased utilization, according to an article published in the American Journal of Roentgenology.

From analog to digital

Breast cancer screening has grown from its rudimentary beginnings in the 1960s to a cornerstone of the U.S.’s public health efforts. Landmark trials such as the 1966 JAMA study led by Phillip Strax demonstrated the effectiveness of screening in reducing breast cancer mortality, triggering the spread of mammography to clinics. However, early mammograms were simply an x-ray with no compression, producing an image that was near unreadable close to the chest wall.

The advent of screening film mammography allowed radiologists to read with more confidence—and as the prevalence of screening rose so did the regulations surrounding it. The President George H.W. Bush signed the Mammography Quality Standards Act into law in 1992, establishing uniform quality standards across the U.S

Another revolution in breast screening happened at the turn of the millennium, with the invention of digital mammography. Breast radiologists were able to ditch the film and adopt digital imaging systems with higher tissue contrast—a boon for women with dense breasts.

However, mammography is on the cusp of another revolution, thanks to digital breast tomosynthesis. DBT takes multiple tomographic images and combines into a “semi-3D image,” enabling radiologists to view slices of the breast, minimizing the obfuscating effect of dense tissue. The FDA approved DBT in 2011 and its usage has been growing ever since, reaching 89 percent of practices in a University of Boulder survey. While it’s still limited in usage within practices, the authors from Yale School of Medicine believe it has the potential to replace standard digital full-field mammography for screening.

Pros and a con

DBT can synthesize traditional 2D mammography from the tomosynthesis data, providing the benefits of both 2D and DBT. The synthesized 2D data is especially useful for comparing images to past studies or looking for calcifications not present in a single DBt slice, instead overlapping into several.

The synthesized 2D images also can smooth the transition from 2D to DBT, providing both the old and new images until the radiologist feels comfortable reading the DBT scans.

One drawback of DBT is the increased reading times when compared to traditional digital mammography. It often requires reading the 2D image along with scrolling through the image slice stack.

“The extra required reading time is an important consideration for practices using high-volume batch interpretation of screening examinations,” wrote the authors. “However, it is important to recognize that the increased time required to interpret a screening examination may be offset by potential time saved downstream during the diagnostic workflow.”

Fewer overall patients are recalled from DBT screening—meaning fewer additional studies. Another time-saving feature is the increased quality of images, giving readers increased confidence in their determinations.

It’s not all positives, however. 

Imaging providers looking to adopt DBT need to take a hard look at their IT infrastructure: DBT file sizers are 10-20 times larger than digital mammography file sizes. The already hefty storage requirement will continue to increase over time as more studies are stored. In addition, old computers may not be powerful enough to display DBT images efficiently and old monitors may not be up to DBT standards for color fidelity and resolution—but modern PACS stations should fulfill the requirements, according to the authors.

Here, there, everywhere

DBT can make an impact in nearly every area of breast cancer, from screening to diagnoses to interventions. Large screening trials have shown greatly improved accuracy, with a recall rate reduction of around 15 percent. It’s also reduced false positive rates, regardless of a women’s age or breast density.

DBT offers a dual benefit in reducing recall rates and increasing cancer detection rate by about 1.5 per 1,000 women screened. According to the authors, Improved specificity and sensititivy could increase over diagnosis for low-grade cancers, but most studies show that recall rates remained low—including a University of Pennsylvania study that reported lowered recall rates for three years after the implementation of DBT.

The upstart modality has diagnostic value as well. While early studies showed DBT to be merely equivalent to conventional diagnostic views, further studies and improvements in DBT revealed distinct advantages.

“Workup of soft tissue lesions is easier, and subtle malignant lesions best seen on DBT may not be reproduced on 2D diagnostic views,” wrote the authors.

They also note the simplification of diagnostic exams, saving time for both patients and providers—yet another workflow improvement harvested from DBT.

The authors believe in the transformative nature of DBT, writing, “Tomosynthesis first entered the breast imaging clinical arena in 2011 and has quickly emerged as a practice-changing standard. The improved accuracy and overall efficiency that DBT can provide will enhance radiologists’ performance and improve the patient experience.”