(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: Build a chest wall phantom to measure and validate dosimetric changes due to a novel tissue expander.
Methods: The phantom base was a CIRs thorax phantom. Dosimeters (OSLDs) were taped to the phantom. 5mm solid thermoplastic was cut, softened, draped over and allowed to harden. OSLDs were placed on top of the thermoplastic and positions marked with permanent marker. A 3D printed solid shell, 5mm thick, was designed with SolidWorksâ„¢ and printed using Raise3Dâ„¢, designed to allow for approximately 1cm of dental wax around all dimensions of the expander except posterior, with spaces for OSLDs at pre-determined locations across the shell, and to fit solidly against the thermoplastic. Dental wax poured into the shell was used to simulate skin and subcutaneous tissue. The fully expanded tissue expander was forced into the melted wax as it cooled. The phantom was scanned, treatment plans created, and treated 5 times with measurements in each location recorded after every fraction for comparison with treatment planning system (TPS) results.
Results: The mean measurement doses for each location fall within 5% of TPS calculated range for all locations with 67% (26/39) falling in the range explicitly, 23% (9/39) falling outside the range but within 3% of the range, and 10% (4/39) falling outside of the 3% but inside the 5% range. When looking at the 195 individual measurements, 60.5% of the measurements fall directly within the range predicted by the TPS, and of the 39.5% that don’t, 83.1% fall within 5% of the range and only 1 measurement was outside of 10% of the range at 11.3% away from the range. Measurements were consistent.
Conclusion: A reproducible chest wall phantom was created and measurements matched the ranges expected by the TPS to within 5%. The TPS appears to model the device correctly.
Funding Support, Disclosures, and Conflict of Interest: This research was partially funded by AirXpanders, Inc.
Keywords
Taxonomy
TH- External beam- photons: Standard field experimental dosimetry
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