ICHNO-ECHNO 2022 - Abstract Book

S54

ICHNO-ECHNO 2022

1). Based on PDD distribution, HU numbers and printing time, the most optimal infill percentage was chosen. A 5 mm thick artificial bolus in the HN region was generated in the TPS Monaco for Alderson's anthropomorphic phantom. After conversion from DICOM to STL file format (that can be read by the printer), the bolus was printed using a fused deposition modelling (FDM) printer with black polyethylene terephthalate glycol (PET-G) and the most optimal infill percentage (Fig. 2).

To assess the clinical application, an IMRT plan was created for artificial bolus. The PTV coverage was V95=99,17%. Then the plan was recalculated for three different configurations: bolus-free, gel bolus and printed bolus. PTV coverage and OAR doses were compared between all configuration-specific calculated plans. The air gaps for the gel and the printed bolus were measured and compared to the generated bolus. Results Dosimetric analysis showed that 40% infill was the most optimal (with 13hrs printing time). The use of 3D printed bolus reduced the size of air gaps by 32% compared to a gel bolus (4.6±1.4 mm vs. 6.8±1.1 mm). For the 3D bolus, the 95% isodose covered the recommended 98% of PTV volume in contrast to gel bolus (V95=99,42% vs. V95=97,31%). In both treatment plans, the OAR doses met the treatment plan acceptance criteria. Conclusion By being able to deal with complex geometries in patients with HN cancer and meeting the radiotherapy objectives, the 3D printed bolus proved to be superior to the gel bolus. While these results are promising, additional research is needed to fully characterize the suitability of the 3D printing technique and materials for boluses and their utility for radiotherapy purposes.