Methodology for the objective assessment of lesion detection performance with breast tomosynthesis and digital mammography using a physical anthropomorphic phantom
Realistic breast phantoms serve as important tools when evaluating full field digital mammography (FFDM) and digital breast tomosynthesis (DBT) system modifications. Current breast phantoms contain either unrealistic features or uniform backgrounds. The purpose of this work was to introduce a novel, task-based methodology for evaluating FFDM and DBT systems using an anthropomorphic inkjet-printed 3D phantom with clinically relevant signals. The methodology consists of multiple physical components: an anthropomorphic breast phantom, microcalcifications made of two types of material, and masses. A 4 cm compressed thickness breast phantom was first modeled analytically, then realized in a slice-by-slice fashion using inkjet printing with iohexol-doped ink. The microcalcifications (MCs) were made by arranging individual specks of varying sizes into regular patterns. Two types of MCs were used, ranging in diameter from 150 μm to 260 μm: one made from calcium hydroxyapatite (HA) and another from soda lime glass microspheres. Lastly, realistically-shaped masses were created using ink doped with potassium iodide. The phantom was imaged on two commercially available FFDM/DBT systems, Holgic Selenia Dimensions and the GE Senographe Essential. A typical mammographic beam was used (according to the automatic exposure control for each commercial system), and a similar average glandular dose was maintained across the systems. A pilot study consisting of a four-alternative, forced-choice (4AFC) analysis with human observers was performed on the FFDM and DBT acquisitions. The linear attenuation coefficients of the microcalcification models were measured to be similar to reference values. A custom Matlab program was created to extract ROI images from images of the phantom, each containing a signal, in preparation for use with 4AFC software. A pilot 4AFC study showed the visibility of the microcalcifications ranged from easy to difficult, and results informed the final reader study. An anthropomorphic breast phantom was created using inexpensive, easily available materials. The task-based assessment was performed on clinical FFDM and DBT systems. This promising phantom generation methodology can be used to objectively evaluate task performance resulting with FFDM and DBT breast imaging systems.
