When simulation becomes real: exploring the characteristics of a 3D-printed power-law phantom in tomosynthesis imaging

Power-law phantoms have been useful for the assessment of imaging properties of breast imaging systems. Recent advances in 3D printing methodologies have enabled printing of 3D objects with density variations, and a physical 3D-printed power-law phantom was created. The purpose of this study was to explore the characteristics of phantom images acquired with a commercial breast tomosynthesis system, and to compare the results with prior findings using breast images. A 3D phantom was printed using PixelPrint. The texture variations in such phantoms are described by the power-law exponent beta. The design beta of the phantom model was 3.4. The printed phantom was imaged on a Hologic Selenia 3Dimensions breast tomosynthesis unit in 2D and 3D imaging modes. Power-spectrum analysis was performed on 2D and 3D images to obtain estimates of beta. Visual inspection of the images revealed grid artifacts in the phantom from the printing process. For power-law analysis, these regions were excluded by applying a mask in the Fourier domain. The observed differences of the power-law exponent in projection and tomosynthesis images (0.24) was similar to those in patient images studies (0.17 to 0.21). Power spectral analysis of a novel 3D-printed power-law phantom resulted in changes of beta in phantom images similar to what was observed in patient data. This indicates that such phantoms predict tomosynthesis image characteristics of breast images.