The interlace deposition method of bone equivalent material extrusion 3D printing for imaging in radiotherapy

Existing material extrusion 3D printing methods of bone-equivalent phantoms for Computed Tomography (CT) imaging in Radiotherapy is limited by the geometrical inaccuracies and the achievable density ranges. The interlace deposition method proposed in this research facilitates the production of densities within the range of polylactic-acid (PLA) and iron-reinforced PLA (Fe-PLA) taking advantage of the dual-extrusion printing in an interlacing pattern with variable layer thickness to fine-tune mean Hounsfield Unit (HU) within a volume of interest. Results show an achieved HU from 63 to 4130 using clinical CT protocols; this result is consistent for all specimen orientations. The proposed method enables the emulation of bone-like HU; as is demonstrated by the manufacture of a patient-specific femur phantom with a mean HU of 173±62 for red bone marrow, 400±64 for cancellous, 1102±182 for cortical, and 56±30 HU for soft tissues. This research demonstrates an inexpensive and clinically-ready approach to constructing bone-equivalent phantoms for imaging and may allow for personalised dosimetry for treatment planning in Radiotherapy.