  Objectives: To compare breast density (BD) assessment provided by an
automated BD evaluator (ABDE) with that provided by a panel of experienced
breast radiologists, on a multivendor dataset.
  Methods: Twenty-one radiologists assessed 613 screening/diagnostic digital
mammograms from 9 centers and 6 different vendors, using the BI-RADS a, b, c,
and d density classification. The same mammograms were also evaluated by an
ABDE providing the ratio between fibroglandular and total breast area on a
continuous scale and, automatically, the BI-RADS score. Panel majority report
(PMR) was used as reference standard. Agreement (k) and accuracy (proportion of
cases correctly classified) were calculated for binary (BI-RADS a-b versus c-d)
and 4-class classification.
  Results: While the agreement of individual radiologists with PMR ranged from
k=0.483 to k=0.885, the ABDE correctly classified 563/613 mammograms (92%). A
substantial agreement for binary classification was found for individual reader
pairs (k=0.620, standard deviation [SD]=0.140), individual versus PMR (k=0.736,
SD=0.117), and individual versus ABDE (k=0.674, SD=0.095). Agreement between
ABDE and PMR was almost perfect (k=0.831).
  Conclusions: The ABDE showed an almost perfect agreement with a
21-radiologist panel in binary BD classification on a multivendor dataset,
earning a chance as a reproducible alternative to visual evaluation.
