Program Information
Comprehensive Morning QA System for Proton Beam Scanning System
H Chung*, K Langen , University of Maryland School of Medicine, Baltimore, MD
Presentations
SU-I-GPD-T-140 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: To design a comprehensive morning QA system for proton beam scanning (PBS) system.
Methods: A comprehensive morning QA system was created for PBS. The QA system consist of a base frame made out of high density polyethylene indexed to the treatment table. On the frame, there is a cube-shaped jig for image registration (2D-3D and CBCT) and laser alignment check. For output check, Sun Nuclear DailyQA3 (Sun Nuclear, Melbourne, FL) detector is used. On the surface of the detector, a dome-shaped build-up was created to deliver a spread out Bragg peak (SOBP) at the detector. The build-up is made out of acrylic with the base diameter of 25.2 cm and height of 15.18 cm. The dome-shaped build-up forces the PBS system to deliver multiple energies (35 energy levels) and increase the sensitivities of the output, spot position, field size, and table position with respect to the beam.
Results: The morning QA can be performed under 20 minutes. For the image registration check, the average KV image registration difference was 0.1 mm (2sigma = +/- 0.6 mm), 0.1 mm (2sigma = +/- 0.7 mm), and 0.1 mm (2sigma = +/- 0.5 mm) for Anterior-Posterior, Superior-Inferior, and Lateral directions, respectively. The average CBCT registration difference was 0.1 mm (2sigma = +/- 0.6 mm), 0.1 mm (2sigma = +/- 0.6 mm), and 0.0 mm (2sigma = +/- 0.8 mm) for Anterior-Posterior, Superior-Inferior, and Lateral directions, respectively. The average relative output was 100.52% (2sigma = +/- 0.75%). Lastly, the dome-shaped build-up design increased sensitivity of field off-set to 3 mm.
Conclusion: The morning QA system for PBS has shown that it can perform image registration (both KV and CBCT) and output measurements under 20 minutes. The sensitivity test showed that the system can detect the radiation field off-set of 3 mm.
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