First approach to ionizing radiation based 3D printing: fabrication of free standing dose gels using high energy gamma photons

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3D printing technique is used for the fabrication of differently shaped objects for industrial, research, medical and societal applications. The technique explores scanning laser beam which interacts with a printing material according to the printing algorithm thus fabricating the required 3D object. In medical field 3D printing is successfully used for fabrication of anatomic bone structures, the first attempts are made to print out artificial skin however there are some limits due to the non-equivalency of printing materials to soft tissue. 3D printing concept might have a big potential in radiotherapy for fabrication of tumor imitators – phantoms for quality control of individual patient treatment.Well known radiation induced polymerization of near tissue equivalent dose gels that are used for dose assessment in radiotherapy is a key issue for the development of the ionizing radiation based 3D printing. However it is to point out, that according to irradiation scenario differently shaped polymerized gel parts usually are being produced inside the gel matrix and cannot be removed from the gel.The aim of this work was to develop high energy photon irradiation based 3D printing method for fabrication of nearly tissue equivalent free-standing 3D dose gel shapes. The first approach for method’s application was fabrication of tumor imitators for brachytherapy treatment.Free standing dose gel shapes that are produced using radiotherapy equipment might serve as medical phantoms (tumour imitators) having the size and shape of a real irradiated volume with dose distribution assessment option within this volume. Concept of this method was firstly proposed in our previous publication (Adlienė et al., 2015).Special dose gels were used as “3D printing material” for the processing of free standing dose gel shapes. Varying dose gel content and adjusting high energy photon irradiation parameters with a pre-planned cancer patient treatment procedure, 3D polymerized gel shapes as the separate free-standing objects were fabricated (3D printing). Comparison of the size and shape of produced 3D objects with the irradiation volumes pre-planned by using standard treatment dose planning system of radiotherapy was performed and the obtained results were analyzed and discussed.