Purpose: To increase the accuracy of electron block shaping and reduce errors associated with creating electron blocks by ensuring correct block positioning, orientation, scale, and applicator selection, through use of a novel and clinically available scripting and 3D printing technique.
Methods: A script was written for a clinical treatment planning system (Eclipse, Varian) to prepare electron block data for creating a 3D-printed mold. This involves scaling, addition of applicator-specific locating holes, and export as a Scalable Vector Graphics (.SVG) file. SVG files were converted to a format compatible with commercial 3D printers (.STL) using free web-based cad software (TinkerCAD). The mold was printed from polylactic acid (PLA) using standard 3D-printing techniques. Blocks were prepared by placing the 3D-printed mold onto a 3D-printed applicator-specific custom mold tray, which utilizes the locating holes in the mold and unique pins in the mold tray to ensure correct applicator size selection and correct block positioning and orientation. With the mold in place, Cerrobend was poured onto the tray, creating an electron block. This workflow was validated by comparing a produced block to the expected block within the treatment planning system for each applicator size to verify correct shape, scale, location, and orientation using visual inspection and caliper measurements.
Results: Electron blocks prepared using this method were found to match the treatment planning system in shape and size to less than 0.2mm. Further, block positioning within the applicator and orientation were also found to match.
Conclusion: Preparation of electron blocks remains a manual process with the potential for errors that can result in mistreatment. By utilizing a novel workflow to 3D-print block molds and custom mold trays, multiple sources of error, such as incorrect block shape, scale, position, and orientation can be eliminated. As a result, a safer and more accurate patient treatment is possible.
Electron Therapy, 3D, Field Shaping
TH- External Beam- Electrons: Development (new technology and techniques)