The 3D printed cutout consisted of five components: the rigid plastic cutout, a copper frame, a flexible lid, a soft protective case, and tungsten ball bearings (BBs; Figure 2 ).
The design took this form to enable it to withstand a drop from 1 m height onto a hard floor without a catastrophic release of BBs into the room. For speed and ease of printing, the cutout was 3D printed using tough PLA plastic, this is the only nonreusable, patient‐specific component. The frame was computer numerical control (CNC) machined from brass or copper (8.5–9.0 g/cm3). The purpose of the frame is to provide shielding of the field edges even when the cutout is slightly underfilled and the gantry is rotated from zero. The lid is printed from carbon fiber reinforced nylon and provides protection to the corners of the cutout component in the event it is dropped. The final part is the protective case, which is 3D printed from a flexible thermoplastic polyurethane (TPU) plastic.
All the template parts were designed in Fusion 360 (Autodesk, San Rafael, CA, USA). Template cutouts were created, which fit the 6 cm × 6 cm and 10 cm × 10 cm electron cones of Varian linacs. Electron apertures were then designed in the Eclipse treatment planning system (Varian Medical Systems) as they would be for any CT‐based treatment plan. The dimensions of the electron aperture was exported from Eclipse and imported into Tinkercad to produce the .stl file of the electron cutout to be printed. The .stl file was exported to Cura (Ultimaker B.V., Utrecht, The Netherlands) for processing prior to transfer to an Ultimaker S5 (Ultimaker B.V.) 3D printer for printing.
After printing, the 3D printed cutout was filled with tungsten BBs with diameters between 1.5 and 2 mm. To reduce air gaps, the cutout was rotated and shaken during the filling process. The separate components of the 3D printed cutout were then assembled. Underfilling is also investigated and discussed in Sections3.2.1 and 4.2 . The 10 cm × 10 cm electron cutout aperture was a 7 cm diameter circle, whereas the 6 cm × 6 cm electron cutout aperture was a 5 cm diameter circle.
The design took this form to enable it to withstand a drop from 1 m height onto a hard floor without a catastrophic release of BBs into the room. For speed and ease of printing, the cutout was 3D printed using tough PLA plastic, this is the only nonreusable, patient‐specific component. The frame was computer numerical control (CNC) machined from brass or copper (8.5–9.0 g/cm3). The purpose of the frame is to provide shielding of the field edges even when the cutout is slightly underfilled and the gantry is rotated from zero. The lid is printed from carbon fiber reinforced nylon and provides protection to the corners of the cutout component in the event it is dropped. The final part is the protective case, which is 3D printed from a flexible thermoplastic polyurethane (TPU) plastic.
All the template parts were designed in Fusion 360 (Autodesk, San Rafael, CA, USA). Template cutouts were created, which fit the 6 cm × 6 cm and 10 cm × 10 cm electron cones of Varian linacs. Electron apertures were then designed in the Eclipse treatment planning system (Varian Medical Systems) as they would be for any CT‐based treatment plan. The dimensions of the electron aperture was exported from Eclipse and imported into Tinkercad to produce the .stl file of the electron cutout to be printed. The .stl file was exported to Cura (Ultimaker B.V., Utrecht, The Netherlands) for processing prior to transfer to an Ultimaker S5 (Ultimaker B.V.) 3D printer for printing.
After printing, the 3D printed cutout was filled with tungsten BBs with diameters between 1.5 and 2 mm. To reduce air gaps, the cutout was rotated and shaken during the filling process. The separate components of the 3D printed cutout were then assembled. Underfilling is also investigated and discussed in Sections
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