Room: Davidson Ballroom A
Purpose: Cerrobend-free solutions for electron field shaping are presented with the advantages of more accurate field shaping, improved safety by imprinting patient information into parts, reduced number of parts, and removal of toxic metals from the clinic.
Methods: 3D printed plastic shells, were designed and manufactured in PLA plastic. For the simple cutouts the workflow is streamlined by using a pre-designed blank tray template for each applicator size (6x6 cmÂ² up to 25x25 cmÂ²) and merging it with the desired field outline. The field edge outlines were exported from the treatment planning system, digitally copied and extruded into a 3D wall. This is then filled with tungsten ball bearings. For the 3D printed MLCâ€™s designs were made, to fit into standard 15x15 cmÂ² or 25x25 cmÂ² Varian electron applicators.
Results: This all-digital workflow ensures accuracy and reproducibility. The difference between the aligned beam profiles of the 3D printed and 15 mm thick Cerrobend cutouts was less than 1.2% at all measured points at 6MeV and 16MeV. The 3D printed cut-outs were centered to within 0.4 mm of the planned outline, whereas the Cerrobend introduced shift errors of 1-3 mm, and shape errors of 0.5-1.5 mm compared to the plan. The 3D printed block is more reliably read by the code reader than the metal frames; the 3D printed tray is a single part and is made to tighter tolerances. Transmission and penumbra width were found to be equivalent to Cerrobend.
Conclusion: Tungsten filled 3D printed cutouts were found to replicate the planned fields with improved alignment accuracy. The 3D printed static electron MLC designs allow for shaping to be done instantly, without the wait for an electron cutout, or CT simulation. These devices improve the accuracy and convenience of electron radiotherapy and open possibilities for novel, more precise electron treatments.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by internal stanford healthcare quality improvement funds.