ESTRO 2022 - Abstract Book

S1327

Abstract book

ESTRO 2022

Conclusion Results showed that PTV coverage and OAR’s doses were comparable. For individual patients CI and HI of PO showed slightly higher values than PRO. MUs for PO were slightly increased as compared to PRO. MU per degree with each individual control points generated by PO showed high degree of modulation compared to PRO. Hence, new PO optimizer can produce comparable degree of plan while using same PRO objectives.

PO-1546 Dosimetric characterization of PLA 3D printed boluses for external beam radiotherapy

M. Pepa 1 , S.G. Gugliandolo 2 , F. Pansini 3 , A. Vavassori 1 , M.G. Vincini 1 , M. Zaffaroni 1 , D. Alterio 1 , S. Rajendran 4 , S.P. Pillai 4 , S. Volpe 5 , G. Marvaso 5 , G. Corrao 5 , F. Cattani 1 , B.M. Colosimo 6 , B.A. Jereczek-Fossa 5 1 IEO European Institute of Oncology IRCCS, Division of Radiation Oncology, Milan, Italy; 2 Politecnico di Milano, Department of Mechanical Engineering; Department of Chemistry, Materials and Chemical Engineering, Milan, Italy; 3 IEO European Institute of Oncology IRCCS, Unit of Medical Physics, Milan, Italy; 4 Politecnico di Milano, Department of Mechanical Engineering, Milan, Italy; 5 University of Milan; IEO European Institute of Oncology IRCCS, Department of Oncology and Hemato-Oncology; Division of Radiation Oncology, Milan, Italy; 6 Politecnico di Milano, Department of Mechanical Engineering , Milan, Italy Purpose or Objective Radiotherapy boluses are able to shift the build-up region and are mandatory to treat superficial lesions. The aim of this study is to produce 3D-printed boluses and evaluate how different process parameters (infill pattern and density, materials, etc.) influence their dosimetric behaviour with respect to a conventional bolus. Materials and Methods A SHAREBOT 42 3D printer (Sharebot, Nibionno, Italy) was used to print boluses, of simple geometry and made of polylactic acid (PLA), to test different combinations of infill densities, printing patterns, and batches of the same material. Duplicates were produced for all printed boluses, which were subsequently irradiated with a 6MV clinical photon beam from Vero ® accelerator system (BrainLAB, Feldkirchen, Germany) and a prescription dose of 2Gy to the surface, using a Gafchromic ® EBT3 film dosimeter placed between RW3 slabs phantom. Measurement films were scanned from 24 to 48 h after irradiation using a desktop flat-bed transmission Epson Expression Scanner 10000 XL and analysed with “film QA-pro” software to compare the maximum dose location for each bolus and for the conventional one. Statistical tests on dose and depth data were carried out to evaluate the influence of each process parameter on the outcome. Results The conventional bolus showed a maximum dose of 195.39 cGy located at (10.5±0.3) mm. Regarding the 3D-printed boluses results are showed in Table 1. A preliminary statistical analysis showed that infill pattern type and density and batch of materials affected the bolus behavior (fig.1). However, in general, values comparable to those of the conventional bolus were obtained with 3D-printed samples. The infill density, as expected, had an important effect on shifting the depth at which the maximum dose was located.