A review on radiological properties of fused deposition modelling material for three-dimensional printing in proton and light ion beam therapy

Background and Purpose: Fused Deposition Modelling (FDM) three-dimensional (3D) printing offers a flexible and economical method for producing radiotherapy phantoms with tailored geometries and material properties. While numerous studies have focused on imaging or photon radiotherapy, research on 3D printing for proton and light ion beam therapy remains limited. Accurate knowledge of the radiological properties of FDM-printed materials is crucial to ensure reliable dose calculation and treatment planning in ion beam therapy. Materials and Methods: A comprehensive literature review was conducted to identify publications reporting relevant radiological parameters, including mass density, computed tomography (CT) number given in Hounsfield units (HU), electron density, and stopping power, for FDM printing filaments. Based on the collected data, an FDM lookup table was generated, summarising the radiological properties of these materials across different printing settings. Results: A total of 17 material classes comprising 70 distinct filaments were analysed and indexed in an open-access lookup table. Polylactic acid (PLA) was the most frequently investigated material, reported in over 34 publications. Among the investigated radiological parameters, the CT number showed the greatest variability for a given material. For samples printed at 100% infill, values ranged from -180 HU to 227 HU for PLA. Recommendations for reducing this variability through standardised reporting are provided. Conclusion: This review provides an overview of FDM 3D printing materials in ion beam therapy. It serves as a practical reference for clinical personnel, medical physicists, and researchers in selecting suitable materials for radiotherapy applications. Moreover, it highlights the need for standardised characterisation methodologies and 3D printing guidelines.