Technical note: Accurate replication of soft and bone tissues with 3D printing.
PURPOSE
The fabrication of a realistic patient-specific skull phantom employing for the first time a new filament extrusion rate method, for the accurate replication of soft and bone tissues both in Hounsfield Units (HU) range and in texture.


METHODS
An in-house developed software was used for the fabrication of the phantom taking into account all the HU of a patient's Computed Tomography (CT) images, replicating the organs voxel-by-voxel without the need of a uniform 3D printing pattern. Two commercially available materials were used; the polylactic acid (PLA) filament for the soft tissues, and a mixture of 50% of PLA and 50% of gravimetric powdered stone for the bone tissues. Additionally, a layer of small amounts of PLA were also extruded on the fabricated bones.


RESULTS
The replicated anatomy of the phantom was very close to the patient's one, achieving a similar range of HU without creating any air gaps and variations on the replicated HU, which are the main artefacts observed when a standard infill density and pattern is employed. The maximum measured HU values of the replicated bone tissues were at about 900.


CONCLUSIONS
The results indicated an accurate replication of the soft tissues HU, and a significant improvement of the bone tissue HU replication. Further investigation on materials of high density in conjunction with the filament extrusion rate method may provide custom-made realistic phantoms for diagnostic and lower energy radiation such as in superficial, orthovoltage and electron beam radiotherapy.