Program Information
Characterizing 3D Printing in the Fabrication of Variable Density Phantoms
J Madamesila*, P McGeachy, J Villarreal-Barajas, R Khan, The University of Calgary, Calgary, AB
Presentations
SU-C-213-2 (Sunday, July 12, 2015) 1:00 PM - 1:55 PM Room: 213
Purpose:
In this work, we present characterization, process flow, quality control and application of 3D fabricated low density phantoms for radiotherapy quality assurance.
Methods:
A Rostock delta 3D printer using polystyrene filament of diameter 1.75 mm was used to print geometric volumes of 2x2x1 cm³ of varying densities. The variable densities of 0.1 to 0.75 g/cm³ were created by modulating the infill. A computed tomography (CT) scan was performed to establish an infill-density calibration curve as well as characterize the quality of the print such as uniformity and the infill pattern. The time required to print these volumes was also recorded. Using the calibration, two low density cones (0.19, 0.52 g/cm³) were printed and benchmarked against commercially available phantoms. The dosimetric validation of the low density scaling of Anisotropic Analytical Algorithm (AAA) was performed by using a 0.5 g/cm³ slab of 10x10x2.4 cm³ with EBT3 GafChromic film. The gamma analysis at 3%/3mm criteria were compared for the measured and computed dose planes.
Results:
Analysis of the volume of air pockets in the infill resulted in a reasonable uniformity for densities 0.4 to 0.75 g/cm³. Printed phantoms with densities below 0.4 g/cm³ exhibited a higher ratio of air to polystyrene resulting in large non-uniformity. Compared to the commercial inserts, good agreement was observed only for the printed 0.52 g/cm³ cone. Dosimetric comparison for a printed low density volume placed in-between layers of solid water resulted in >95% gamma agreement between AAA calculated dose planes and measured EBT3 films for a 6MV 5x5 cm² clinical beam. The comparison showed disagreement in the penumbra region.
Conclusion:
In conclusion, 3D printing technology opens the door to desktop fabrication of variable density phantoms at economical prices in an efficient manner for the quality assurance needs of a small clinic.
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