A Dosimetric Evaluation of 3D-Printed Thermoplastic Polyurethane (TPU) for Use as a Custom Breast Bolus
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PO-GePV-T-351 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: This study aims to compare the dose measurements at the surface of solid water with a traditional sticky bolus and a 3D printed thermoplastic polyurethane (TPU) bolus. The effect of inter-print variability and different print parameters was also investigated.
Methods: Two 15x15 cm² sheets of TPU bolus were printed with thicknesses of 5 and 10 mm. The prints used 100% infill, however some boluses were reprinted using different flow settings to enhance print quality. Each bolus was stacked on top of 10 cm of solid water and irradiated with 6 MV photons and 6 MeV electrons. A plane parallel chamber was placed at an SAD of 100 cm on the central axis directly under each bolus to measure the dose. Measurements were taken in open conditions, and under TPU bolus, traditional bolus, and solid water for each thickness as well as stacked to create a 1.5 cm thickness.
Results: The dose under the TPU bolus had a smaller percent deviation from solid water than with traditional bolus in five of the six conditions tested. All deviations with TPU were below 5%, while some deviations with traditional bolus were up to 8%. The difference in deviation from solid water of prints with the same parameters was less than 0.5% with both photons and electrons. The flow percent change of 15% yielded a 4% dose difference with photons and a 1% difference with electrons.
Conclusion: In this study, TPU showed appropriate dosimetric qualities to be used as bolus. It was also shown that there is a negligible difference between prints with the same parameters and a significant difference between prints with different values of flow percent.
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