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SU‐E‐T‐792: Validation of a Secondary TPS for IROC‐H Recalculation of Anthropomorphic Phantoms
Author(s) -
Kerns J,
Howell R,
Followill D,
Melancon A,
Stingo F,
Kry S
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4925156
Subject(s) - imaging phantom , monte carlo method , nuclear medicine , linear particle accelerator , beam (structure) , radiation treatment planning , dosimetry , physics , medical physics , mathematics , medicine , optics , statistics , radiation therapy , radiology
Purpose: To validate a secondary treatment planning system (sTPS) for use by the Imaging & Radiation Oncology Core‐Houston (IROC‐H). The TPS will recalculate phantom irradiations submitted by institutions to IROC‐H and compare plan results of the institution to the sTPS. Methods: In‐field dosimetric data was collected by IROC‐H for numerous linacs at 6, 10, 15, and 18 MV. The data was aggregated and used to define reference linac classes; each class was then modeled in the sTPS (Mobius3D) by matching the in‐field characteristics. Fields used to collect IROC‐H data were recreated and recalculated using Mobius3D. The same dosimetric points were measured in the recalculation and compared to the initial collection data. Additionally, a 6MV Monte Carlo beam configuration was used to compare penumbrae in the Mobius3D models. Finally, a handful of IROC‐H head and neck phantoms were recalculated using Mobius3D. Results: Recalculation and quantification of differences between reference data and Mobius3D values resulted in a relative matching score of 12.45 (0 is a perfect match) for the default 6MV Mobius3D beam configuration. By adjusting beam configuration options, iterations resulted in scores of 8.45, 6.32, and 3.52, showing that customization could have a dramatic effect on beam configuration. After in‐field optimization, penumbra was compared between Monte Carlo and Mobius3D for the reference fields. For open jaw fields, FWHM field widths and penumbra widths were different by <0.6 and <1mm respectively; for MLC open fields the penumbra widths were up to 1.5mm different. Phantom recalculations showed good agreement, having an average of 0.6% error per beam. Conclusion: A secondary TPS has been validated for simple irradiation geometries using reference data collected by IROC‐H. The beam was customized to the reference data iteratively and resulted in a good match. This system can provide independent recalculation of phantom plans based on independent reference data.