Radiologists’ visual search patterns affected by breast density

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 - breast density search patterns
(a) Lesion overlying the fibroglandular dense tissue in a low-density mammogram; (b) lesion outside the fibroglandular dense tissue in a low-density mammogram.
Source: Academic Radiology 2014;21:1386–1393

Could the presence of dense breast tissue regions make radiologists more attentive during interpretation? A new study suggests this might be the case as increased breast density of a patient seemed to improve the visual search process of experienced radiologists in locating lesions on digital mammography.

While high mammographic density is linked to increased breast cancer risk and can obscure the presence of lesions, Dana S. Al Mousa, MSc, of the University of Sydney, and colleagues noted that in the digital era, there is limited data on the effect of mammographic density on breast radiologists’ reading patterns.

“If we wish to optimize viewing algorithms or design appropriate training strategies, the impact of breast density on radiologists’ behaviors needs to be better understood,” Al Mousa and the research team wrote.

The findings were published in the November issue of Academic Radiology.

A total of 149 craniocaudal digital mammograms were studied by seven radiologists, five of whom specialized in breast radiography. Seventy-five of the mammograms were malignancy free while 74 were cases with a total of 75 cancers—45 masses without calcification, 12 architectural distortions, 14 focal asymmetries, and four calcification lesions. As the radiologists read the mammograms, observer search patterns were recorded.

Total time examining each case, time to identify first lesion, dwell time and number of hits per area were calculated.

When lesions overlaid fibroglandular tissue, cases with high breast tissue density featured increased location sensitivity for all radiologists in the study compared to cases with low tissue density.

Detection speed also was impacted by tissue density and lesion location. “A main finding in our study was that radiologists tend to detect the lesions overlying fibroglandular dense tissue significantly faster than lesions outside the fibroglandular dense tissue, and this was significant for both high- and low- density cases,” Al Mousa and colleagues wrote.

The study found for low-density cases, radiologists took about 2.28 seconds to first fixate the lesion when it was overlying the dense area and 8.44 seconds when it was outside. For the high-density cases, radiologists took a median time of 7.96 seconds to first fixate the lesion when it was overlying the dense tissue and 12.63 seconds when it was outside.

“This suggests that dense areas of breast parenchyma act as an attractor for the radiologists’ visual attention,” the study stated.

Overall, lesions in the study that were overlying dense breast tissue took less time to be first located, had significantly longer dwell time and attracted greater number of fixations compared to lesions located outside the fibroglandular dense regions of the breast tissue, in both low and high-density mammograms.