Evaluation of Image Quality in Digital Mammography and Digital Breast Tomosynthesis: Phantom Observer Study From American College of Radiology Imaging Network PA 4006
M Thomas*, Y Matsutani, E Conant, A Maidment, Univ Pennsylvania, Philadelphia, PASU-C-116-6 Sunday 1:00PM - 1:55PM Room: 116
Purpose: Determine contributing factors for image quality in 2D and 3D from comparison of phantom scores and image acquisition parameters.
Methods:Tomosynthesis 2D and 3D quality assurance images of the ACR Mammography Accreditation Phantom were obtained as part of the American College of Radiology Imaging Network PA-4006 trial. Imaging was performed on Selenia Dimensions (Hologic, Bedford MA) systems at the Hospital of the University of Pennsylvania (n=176) and Einstein Medical Center, Philadelphia, PA (n=70). Four trained observers scored all available images according to manufacturer's instructions; image order was randomized by case number and modality for each observer. For tomosynthesis, observers selected the slice level maximizing conspicuity. Paired t-test compared FFDM and DBT cumulative scores by site, multivariate regression related device parameters to image quality, and multi-observer Kappa assessed interobserver agreement.
Results:Fiber scores were higher for 3D than 2D at site B (p<0.001) with no difference at site A. Speck and mass scores were greater for 2D than 3D at both sites (p<0.001). At site A, regression analysis demonstrated positive correlation of exposure (mAs) with 2D mass, 3D fiber and 3D mass scores; no significant correlations were found for site B. Absolute level of interobserver agreement was highest for specks, followed by fibers and masses. There was substantially lower inter-observer agreement for specks in 3D than 2D; the agreement between 2D and 3D for fibers and masses did not change significantly.
Conclusion:Phantom scores differed significantly between 2D and 3D imaging; fibers were better visualized in 3D, while specks and masses were better visualized in 2D. Observers stated that scoring specks in 3D was more challenging; this is supported by the observation that inter-observer agreement was significantly poorer in 3D than 2D only for specks. There are many factors that influence scoring. While phantom score was partially predicted by exposure, other factors were involved.