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Electron Field Shaping with a Three-dimensional-printed, Tungsten-infused Multileaf Collimator: A Practical,
M K Farris1, R T Hughes1, I Wood1
1Department of Radiation Oncology, Wake Forest University School of Medicine, Winston-Salem, North Carolina.
Purpose:
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.
Methods And Materials:
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.
Results:
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.
Conclusions:
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.
