Preliminary Investigation of the Dosimetric Impact of Common Dental Restorative Materials On Proton Beams
A Gomez1*, M Leyva2, L Coutinho1, E B Rosen1, N Kalman1, M Hobson1, (1) Miami Cancer Institute, Baptist Health South Florida, Miami, FL, (2)Provision Cares Proton Therapy Center,Knoxville, TN,
Presentations
PO-GePV-T-132 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: To quantify the dosimetric impact of 70 MeV proton beams in the vicinity of materials commonly used in current dental practice.
Methods: Two-millimeter-thick metallic, Titanium (Acnis), Cobalt-Chromium (MESA), and Zirconium (Nacera), and non-metallic, PEEK (Juvora), Pekkton (Cendres+Metaus), and PMMA, samples were studied. A uniform monoenergetic 70 MeV scanned proton field was delivered by an IBA ProteusPLUS PBS proton therapy system (Ion Beam Applications, Louvain‐la‐Neuve, Belgium). Samples were placed 60 mm apart edge-to-edge in a 3D printed tray on top of a 10x25x25 cm3 block of solid water with an additional 1, 2, or 3 cm of solid water added to the top surface. Relative profiles were measured using Gafchromic EBT3 film placed immediately proximal or distal to the sample tray and normal to the beam direction. Pixel values in regions of interest (ROIs) (1x1 cm2) centered at and in the absence of the materials were averaged and compared.
Results: Backscatter measured directly at the entrance surface was negligible compared to measurements made in absence of the samples, with relative pixel value differences (RPVDs) of -1.2%±1.4% to 0.9%±1.5%. The dose effects at the distal surface were greater for metals than for nonmetals, with RPVDs for non-metals ranging from -1.7%±1.5% to 0.9%±1.3% and -25.7%±1.5% to 61.9%±2.2% for metals.
Conclusion: Metallic dental restorations can cause downstream dose perturbations with the extent dependent on the material and position of the material relative to the Bragg peak. Future work will include validating these results with ion chamber measurements and with additional energies with and without the presence of a range shifter and comparing measurements to the WET of samples to examine dose perturbations from secondary interactions.
Funding Support, Disclosures, and Conflict of Interest: Credit Panthera Dental Lab as they prepared all the samples to Evan Rosen at no cost.
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