Evans et al. (2016) showed that radiologists can classify the mammograms as normal or abnormal at above-chance levels after a 250-ms exposure. Our study documents a similar gist signal in digital breast tomosynthesis (DBT) images. DBT is a relatively new technology that creates a three-dimensional image set of slices through the volume of the breast. It improves performance over two-dimensional (2-D) mammography but at a cost in reading time. In the experiment presented, radiologists (N = 16) viewed “movies” of DBT images from single breasts for an average of 1.5 s per case. Observers then marked the most likely lesion position on a blank outline and rated each case on a six-point scale from (1) certainly normal to (6) certainly recall. Results show that radiologists can discriminate normal from abnormal DBT cases at above-chance levels as in 2-D mammography. Ability was correlated with experience reading DBT. Observers performed at above-chance levels, even on those images where they could not localize the target, suggesting that this is a global signal that could prove valuable in the clinic.
Digital breast tomosynthesis (DBT) is beginning to be used more frequently alongside full-field digital mammography (DM) in routine breast cancer screening. However, little is known about radiologists’ search strategies reading DBT. This study aims to measure radiologists’ eye movements prior to testing search strategies intended to make DBT faster and/or more accurate. Twelve observers (board certified breast radiologists or current women’s imaging fellows) were instructed to search for lesions as they would report during normal clinical conditions. Observers were shown a single view of a single breast for each case and informed that this was an enriched study (10 positive cases out 20). Eye tracking used a SMI RED250mobile Eye Tracker sampling at 250Hz. Tracking error was below 0.5 deg. There was an increase in the detection rate/accuracy and decrease in false positives with DBT compared to DM. There was a longer search time in DBT compared to DM, with a shorter saccade length shown in DM. Different observers where shown to have differing search patterns however it was not possible to show any observer to have a true driller or scanner technique. Results generally replicated previous studies however; more work would be needed to obtain conclusions as to optimal search strategies.