Dosimeter Characteristics of 3D Printed Boluses
R Li1*, M Li2, C Song1, S Tafon Penn1, N Deb1, T Xue1, (1) ST LUKE'S UNIVERSITY HEALTH NETWORK, Bethlehem, PA, (2) Parkland High School,
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(Saturday, 3/26/2022) [Central Time (GMT-5)]
Purpose: To measure and compare the dosimeter characteristics of 3D printed boluses with boluses made of other materials.
Methods: The 3D Printed bolus effectiveness is evaluated by measuring and comparing the electronic charges underneath the boluses. Flat boluses with thickness of 0.5 cm and 1 cm were printed with sizes covering a radiation field of 10x10 cm. The boluses were made of either Poly Lactic Acid (PLA) or Silicone. A parallel plane ionization chamber (Markus) embedded in a solid water phantom was covered by these boluses and supported by thick back-scattering phantom. Using Varian TrueBeam LINAC, electronic charges were collected with a setup of 100 SSD to bolus surface and 10x10 cm field size with photon beam energies of 6 MV and 10 MV, electron beam energies of 6 MeV, 9 MeV, 12 MeV, 16 MeV and 20 MeV, each irradiation gave 50 MU. With same setup, the measurements repeated using other boluses made of solid water and wet towel.
Results: Compared with solid water, 3D printed boluses made of both PLA and Silicone have very close dosimeter characteristics with both thickness of 0.5 cm and 1 cm for all the photon and electron energies beams. The maximal difference for photon beams is less than 1 %, and less than 2.5% for electron beams. On the other hand, because of less accuracy of wet towel thicknesses, the differences between wet towel and solid water are relatively large. Photon beams has rapid buildup regions, the differences are much larger than those of electron beams.
Conclusion: 3D printed boluses have very close photon and electron attenuation characterizes as compared with solid water, which are tissue equivalent.
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