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Proton Beam Imaging Using X-Ray Flat Panel for a Pencil Beam Scanning System

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C Finley

C Finley1,2*, K Jee1 , T Zwart3 , G Sharp1 , W Huo1 , M Jones3 , K Huang3 , D Catanzano3 , S Nyamane3 , J Cooley3 , S Rosenthal3 , H Lu1 , (1) Massachusetts General Hospital, Boston, MA, (2) University of Massachusetts Lowell, Lowell, MA, (3) Mevion Medical Systems, Inc, Littleton, MA


TU-L-GePD-J(B)-6 (Tuesday, August 1, 2017) 1:15 PM - 1:45 PM Room: Joint Imaging-Therapy ePoster Lounge - B

Purpose: Recent studies have shown that proton beam imaging could be achieved using an X-ray flat panel for passive scattering systems. It was also suggested that such imaging can be performed for pencil beam scanning (PBS) systems by taking energy-resolved dose measurements. Here we combined the two techniques, i.e., energy-resolved measurement and X-ray flat panel detector, to investigate the feasibility of proton beam imaging using HYPERSCAN, a PBS system by Mevion Medical Systems (Littleton, MA).

Methods: The scanning layers for imaging beam were selected in the energy range of 50 to 185 MeV, with the maximum range in water of 22 cm and layer spacing of 1.6 cm. Measurements using ion chambers were first conducted in order to find the proper imaging beam with appropriate dose to the imaging panel by reducing beam current. Imaging data were then taken using the fluoroscopy flat panel (4030E, Varian Medical Systems, Palo Alto, CA) for solid water phantom with a range of water equivalent path length (WEPL) values (0.6-20 cm). These data were processed to build the calibration dataset, where the dose distribution as a function of scanning layer energy has a unique form for each WEPL value. Several phantoms were then imaged including a Gammex CT calibration phantom with various tissue-equivalent inserts, an anthropomorphic head phantom and a plastic hand model.

Results: Imaging acquisition for the flat panel worked as expected without apparent damage to the amorphous silicon panel. Initial processing of the imaging data for the calibration run showed reasonable results. The beam current for the imaging beam was below the normal range for therapy operation and improvement in control accuracy may be needed.

Conclusion: Proton beam imaging using HYPERSCAN system has been tested with reasonable success.

Funding Support, Disclosures, and Conflict of Interest: Some authors are employees of Mevion Medical Systems, Inc.

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