Feasibility of clinical electron beam formation using polymer materials produced by fused deposition modeling

The main challenge in electron external beam radiation therapy with clinical accelerators is the absence of
integrated systems to form irregular fields. The current approach to provide conformal irradiation is to use
additional metallic shaping blocks, with inefficient and expensive workflows. This work presents a simple
method to form therapeutic electron fields using 3D printed samples. These samples are manufactured by fused
deposition modeling, which can affect crucial properties, such as material homogeneity, due to the presence of
residual air-filled cavities. The applicability of this method was therefore investigated with a set of experiments
and Monte Carlo simulations aimed at determining the electron depth dose distribution in polymer materials.
The results show that therapeutic electron beams with energies 6–20 MeV can be effectively absorbed using
these polymeric samples. The model developed in this study provides a way to assess the dose distribution in
such materials and to calculate the appropriate thickness of polymer samples for therapeutic electron beam
formation. It is shown that for total absorption of 6 MeV electron beams the material thickness should be at least
4 cm, while this value should be at least 8 cm for 12 MeV and 11 cm for 20 MeV, respectively. The results can be
used to further develop 3D printing procedures for medical electron beam profile formation, allowing the
creation of a collimator or absorber with patient-specific configuration using rapid prototyping systems, thus
contributing to improve the accuracy of dose delivery in electron radiotherapy within a short manufacturing
time.