Electron Field Shaping with a Three-dimensional-printed, Tungsten-infused Multileaf Collimator: A Practical, Low-cost, Reusable, and Customizable Alternative to Traditional Cutouts.

Abstract

Current electron field shaping methods, such as milled copper cutouts and Cerrobend plates, are limited by toxic materials, recurring costs, and long turnaround times. To circumvent these issues, we designed a 3-dimensional-printed electron multileaf collimator (eMLC) that uses tungsten-infused polyethylene terephthalate glycol (W-PETG), a filament developed specifically for radiation therapy, to create the leaves. This study described the feasibility assessment of this device to shape electron fields. We first characterized the attenuation properties of W-PETG using stacks of variable thickness blocks (0.1-1 cm, flat 10 × 10 cm²) placed in a solid water phantom with a parallel plate chamber. Attenuation of 6 and 15 MeV electron beam energies was tested using various plate thicknesses. A prototype eMLC was designed to mount within a standard Elekta 14 × 14 cm² cone. The carriage was printed using generic PETG; interlocking leaves were printed using W-PETG. Interleaf and leaf-end leakage were evaluated using 1000 monitor units (MU) delivered through closed leaves. A clinical Cerrobend field was recreated with the eMLC, and both were compared using radiochromic film exposed to 200 MU using 6 and 15 MeV electron beams. W-PETG blocks of 1 cm thickness reduced 6 and 15 MeV electron beams to below 5% transmission. No measurable interleaf or end-to-end leaf leakage was detected at either energy using 1000 MU exposures. The eMLC resulted in a dose distribution nearly identical to Cerrobend. Compared with Cerrobend, the eMLC-generated fields demonstrated approximately 15% smaller penumbra and sharper field edges. This novel 3-dimensional-printed eMLC using W-PETG provides dose-shaping characteristics comparable with conventional cutouts, with no detectable leakage and improved edge definition. Fabricated with consumer-grade equipment, this device provides reusable, customizable field shapes that may be suitable for clinical use. Further study of its validation and implementation into clinical workflows is warranted.