Manufacturing of physical breast phantoms with 3D printing technology for X-ray breast imaging

Recently we have started a project for virtual clinical trials in 2D (digital mammography, digital breast tomosynthesis) and 3D (dedicated breast computed tomography) X-ray breast imaging using Monte Carlo simulations and digital (computational) breast phantoms. In this framework we envisaged the manufacturing of physical versions of the digital phantoms, using 3D printing technology. Due to the possibility of using more than one material for object printing, we adopted the common Fused Deposition Modelling (FDM) technique, where a filament of thermoplastic material is first melted and then extruded onto a support plate in order to create the individual layers of a model, following a 3D digital representation of the object. Digital (computational) breast models (phantoms) of the uncompressed breast were created from 3D breast images acquired with a breast CT clinical scanner developed at UC Davis. A segmentation algorithm was developed with voxels classified as air, skin, adipose and glandular tissue. Physical phantoms were printed in three components: PVA, ABS and Nylon filament materials, whose X-ray attenuation simulates the attenuation at 60 keV of skin, adipose and glandular tissues, respectively. By software compression of those digital models we derived phantoms simulating the compressed breast; PET and ABS materials were selected to 3D print the corresponding phantoms, simulating the attenuation at 30 keV of skin, glandular and adipose tissues. The physical phantoms will be adopted for validation measurements in dosimetry and image quality assessment, and for comparison with in-silico, Monte Carlo studies in digital mammography, digital breast tomosynthesis and breast computed tomography.