How synthetic mammography falls short compared to FFDM

The combination of full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT) can improve patient care during breast cancer screening, but performing both examinations does lead to more radiation and a longer acquisition time. Providers can now reconstruct 2D images from a patient’s DBT dataset during a process known as synthetic mammography (SM), making the additional FFDM examination unnecessary. However, according to new research published in Academic Radiology, some screen-detected cancers are less conspicuous on SM than FFDM.

“Although overall call back rates and sensitivities/specificities of DBT with SM vs. FFDM have been reported, concerns about SM include whether the image quality of SM is equivalent to FFDM, with the understanding that SM is read in conjunction with a DBT dataset,” wrote Sona A. Chikarmane, MD, department of radiology at Brigham and Women’s Hospital in Boston, and colleagues. “In addition, only a few studies have looked at the conspicuity and mammographic features of findings on SM and FFDM, using mixed diagnostic and screening populations or small sample sizes of malignancies.”

Chikarmane et al. explored data from 181 cancer patients who underwent FFDM plus DBT and SM from Oct. 1, 2015, to June 30, 2017. Three radiologists reviewed each patient’s examinations, scoring if the screen-detected cancer was more or less conspicuous on SM compared to FFDM.  

Overall, 76% of findings were “equal or more conspicuous” on SM and FFDM. Calcifications and asymmetries less than 2 cm wide, however, were less conspicuous on SM.

“Reasons for why size contributes to conspicuity on screening SM vs. FFDM include the inherent ability of mammography to detect larger findings,” the authors wrote. “In addition, morphology of calcifications and asymmetries (i.e. amorphous calcifications or irregular asymmetries) likely contribute to visibility in relation to size; for example, smaller groups of amorphous calcifications may be more difficult to detect than larger groups of coarse heterogenous calcifications.”

Also, 12% of all findings were reassessed as “a less conspicuous mammographic feature” on SM compared to the FFDM images. The team noted that, based on this finding, “radiologists should take caution when assessing one-view findings on SM.”

Chikarmane and colleagues added that SM technology is still evolving; this is an area researchers must continue to focus on over time.

“It is conceivable that as SM software improves, the conspicuity of certain malignant morphologies on SM may improve,” the authors concluded. “At this time, given the importance of radiation dose reduction when utilizing SM vs. FFDM, further studies are needed to analyze long term outcomes of SM in the screening population.”