(Thursday, 7/18/2019) 10:00 AM - 12:00 PM
Room: 301
Purpose: 3D printing methods are becoming increasingly popular in the radiotherapy field due to their customizability and low cost. One potential use is printing custom plastic holders for gel dosimeters for use in patient-specific QA. However, oxygen inhibition of gel dosimeter response is a concern. This work investigates oxygen contamination of polymer gel dosimeters through different thicknesses of 3D printed plastic containers.
Methods: Nine 3D-printed plastic test tubes of different thicknesses (3-1 mm tubes, 3-1.5 mm tubes, and 3-2 mm tubes) and three glass test tubes were filled with NIPAM polymer gel and sealed with septa. Each tube was irradiated using a 6 MV Varian Clinac 21EX linear accelerator to 30 Gy at a depth of 5 cm in water. Dose data were acquired using a Varian Agilent 4.7 T MRI scanner. An MSE pulse sequence with a TE of 22 ms, a TR of 600 ms, and 16 averages was used, resulting in an image resolution of 0.3 mm x 0.3 mm, slice thickness of 1 mm and a 1 mm slice separation.
Results: An average response profile was acquired for each tube. Three average response profiles from each 3D printed plastic thickness were averaged and compared to the average response profile of the glass tubes. The distance from the wall to 95% response was used as a metric to compare depth of oxygen inhibition. The average difference from glass were 0.2 mm±0.3 mm, 0.1 mm±0.3 mm and 0.0 mm±.3 mm for the 1, 1.5 and 2 mm tubes, respectively.
Conclusion: Oxygen inhibition of NIPAM polymer gel is minimal at thicknesses as thin as 1 mm. The 3D-printed plastic containers used in this study are suitable for use with NIPAM polymer gel dosimeters.
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