ESTRO 2024 - Abstract Book

S2089

Clinical - Sarcoma, skin cancer, melanoma

ESTRO 2024

We printed using an Axiom 20 3D printer with 2.85 mm PolyDissolve PVA filament manufactured by PolyMaker. Infill settings for the print can be varied but if support is needed it can only be touching the build plate else it may block inside the mould. Three moulds of different sizes were created for patients receiving electron therapy to skin near their eyes and nose. The shields were imaged with 6MV photons to observe for defects and OSLD nanoDots were placed under the shield to determine dose to critical organs. Shields made with lead using older methods were also produced comparison and backup.

Results:

No defects were found in any shield and dose reported by the OSLD measurements were less than 5% of the prescription dose. The accuracy of the cutout was confirmed by registering the MV and CT images in the TPS and found to accurately fit the wired contours in all three shields. One shield was not used for patient treatment and the lead shield used instead due to changes in the treatment area determined by the physician and ease of snipping lead. Each case required between 2 and 5 days from finishing the plan to having a finished shield. The majority of the time did not need the attention of staff. Active time needed to create the custom shield includes times for design, setting up the print, removing the print, pouring the Cerrobend, submerging the mould, and taping. Designing is variable and can take up to an hour, but the others require about 45 minutes of staffing hours. The additional time needed to print and dissolve the mould may require several days depending on the printer capabilities and size and thickness of the PVA mould.

The shields were easy to align to the patient anatomy and in 2 cases a custom 3D printed bolus was designed to fit snuggly to the cutout. Patients did not experience any discomfort caused by the shield.