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A Novel Integrated Quality Assurance Phantom for Radiographic and Nonradiographic Radiotherapy Localization and Positioning Systems

T Fowler

T Fowler*, Amy S Yu , Standford Cancer Center, Stanford, CA


MO-DE-FS1-2 (Monday, July 31, 2017) 1:45 PM - 3:45 PM Room: Four Seasons 1

Purpose: Various localization and positioning systems with the use of radiographic or non-radiographic methods have been developed to improve the accuracy of radiotherapy. However, there is no single integrated phantom for the different systems. Each quality assurance (QA) is independent to each other, so the deviation between each system is unavailable. The purpose of this work is to develop and evaluate an integrated QA phantom for different localization and positioning systems.

Methods: The integrated phantom was designed in 3D CAD software and 3D printed. The phantom was designed with laser alignment marks, a raised letter “S” on the anterior surface for Optical Surface Monitoring System (OSMS®) registration, a core for radiofrequency (RF) beacon tracking system (Calypso®) alignment, eight internal fiducials for image alignment, and an isocentric bearing for Winston-Lutz test. Tilt legs and rotational stage were designed for rotational verification of OSMS and RF beacon systems, respectively. The phantom was scanned using CT scanner and a QA plan was created. This prototype phantom was evaluated against to our established QA procedure.

Results: The QA result between the proposed phantom and daily QA phantoms are, respectively, 1.3 and 1.4 mm for Calypso, 0.4 and 0.4 mm for OSMS and 0.16 and 0.16 mm for Winston/Lutz. The laser alignment agrees within 0.5 mm. The accuracy of rotational verification for OSMS and RF beacon is less than 0.5 degree compared the predefined value.

Conclusion: We have designed and evaluated a novel integrated phantom for radiographic and non-radiographic localization and positioning systems for radiotherapy. With this phantom, we will reduce the variation in measurements and simplify QA procedures.

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