Evaluation of the visual realism of breast texture phantoms in digital mammography

A number of different physical and digital anthropomorphic breast phantoms have been proposed to assess and optimize the performance of breast x-ray imaging systems. All mimic, to some extent, different characteristics of the breast but a systematic realism of phantom realism applied to a number of phantoms using human readers has not been performed, for either full field digital mammography (FFDM), or digital breast tomosynthesis (DBT). We present a reader study in which radiologists performed a subjective evaluation of the visual realism between a selected group of available software phantoms (Stochastic Solid Breast Texture (SSBT) and power law noise texture), physical phantoms (CIRS BR3D breast imaging phantom and the L1 phantom) and clinical mammography images. Regions of interest (ROIs) of 2×2 cm² and 2×2×3 cm³ , for FFDM and DBT stacks respectively, were scored. The readers were asked to judge how well the ROIs represented real breast texture using a 5-point rating scale. Observer ratings were analysed using the receiver operating characteristic (ROC) methodology and the area under the ROC curve (AUC) was used as the figure-of-merit (FOM). The Mann-Whitney test was used to assess the differences between separate groups. For the question of breast texture realism, the SSBT and power-law noise texture images obtained a high score. For DBT, SSBT was also found to have a high visual realism while the power-law noise texture images were found to have mediocre visual realism.