Assessment of DBT acquisition parameters for 2D and 3D search tasks.

A concern with using mathematical model observers to gauge medical image quality is whether and to what degree task simplifications can affect study outcomes. Researchers are interested in assessments based on clinically realistic tasks, but routinely implement simplified tasks to manage time and computation. The goal of this work is to examine how optimization of digital breast tomosynthesis (DBT) acquisition parameters can be influenced by the consideration of 2D or 3D search tasks. Localization ROC (LROC) observer studies were based on simulated image slices and volumes obtained from low- and medium-density digital breast phantoms containing 8-mm spherical masses. An analytic cone-beam projector used an acquisition arc of 60 degrees while the number of angular projections varied from 3 to 51. Image volumes were reconstructed with the Feldkamp FBP algorithm and then postfiltered and thresholded to eliminate negative pixel values. A visual-search (VS) model observer was applied for both the 2D and 3D LROC studies. The observer used 2D spatial derivatives as features to find suspicious candidate locations in an image. The candidates were compared by means of a binary Hotelling discriminant. Preliminary results indicated substantially reduced performance with the 3D task, particularly for the more-dense cases.