ESTRO 2023 - Abstract Book

S1468

Digital Posters

ESTRO 2023

Conclusion Our results indicate that anthropomorphic digital phantoms can be valuable tools in treatment planning optimisation for upright positioning geometries. Future benchmarking and refining work will be performed using additional data from volunteers’ CT and ultrasonography scans for statistical analysis. In addition, we plan to model lung and diaphragm motions in the upright positioned phantoms during breathing process.

[1] Takazakura et al. 2014. J Magn Reson Imaging. 19:605-9.

[2] Segars et al. 2010 MedPhys 37(9) :4902-4915

[3] Hayes et al. 2013. Comput Math Methods Med. 2013:419821

PO-1748 Optimal printing parameters and dosimetric evaluation of patient-specific 3D printed bolus

B. Qi 1 , T. Risse 1 , G. Guibert 1 , P. Weber 1

1 Réseau Hospitalier Neuchâtelois, Radiation Oncology, La Chaux-de-Fonds, Switzerland

Purpose or Objective The work aims to define water-equivalent 3D printing parameters for patient-specific bolus and to evaluate the use of 3D printed bolus on an anthropomorphic phantom. Materials and Methods 17 slabs of 10 × 10 × 1 cm3 with different printing orientation, infill patterns, infill densities and layer thicknesses were printed with brick red Z-PLA-Pro (Zortrax) on a Zortrax M300 Dual 3D printer. For film dosimetry, the samples were first CT scanned (Philips Brilliance 64) with 5cm backscattered Plastic Water DT plates (CIRS) under them and images were transferred to the TPS (Philips Pinnacle v16.2). 2 Gy was planned using 6 MV photon beam on the TPS. The electronic density of all the samples was overridden to 1 g/cm3. The homogeneity and dose distributions were analyzed according to the standard deviation and the average value of measured dose. The clinical use of 3D printed bolus has been tested with an anthropomorphic phantom (STEEV, CIRS). Several boluses with different printing parameters were printed and the one with the highest printing quality was used and compared with a wax bolus, a standard bolus and without bolus. A treatment of 2Gy on a superficial tumor on the nose was planned for all bolus configurations. Finally, the STEEV phantom was irradiated with film fixed on the nose surface. Results The film tests showed good correlation between physical density and dose delivered. Physical density was influenced by infill pattern, infill density, printing orientation and layer thickness. All slabs with infill density ≥ 70% had standard deviation of measured dose similar to the homogenous plastic water and thus inner inhomogeneity could be ignored; grid pattern was chosen because of shorter printing time. Dose difference between slabs printed in horizontal and vertical direction was below 5% and ignorable. 0.2 mm layer thickness was chosen for higher printing quality. The PLA-Pro sample with grid