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Experimental Validation of the Monte Carlo Model of HYPERSCAN™ Pencil Beam Scanning System for Proton Beam Imaging and Radiation Treatment

W Huo

W Huo1,2*, T Zwart3 , C Finley1 , K Jee1 , G Sharp1 , S Rosenthal3 , X Xu2,4 , H Lu1 , (1) Massachusetts General Hospital, Boston, MA, (2) University of Science and Technology of China, Heifei, Anhui, (3) Mevion Medical Systems, Inc, Littleton, MA, (4) Rensselaer Polytechnic Institute, Troy, New York


SU-I-GPD-T-196 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The HYPERSCAN™ (Mevion Medical Systems, Littleton, MA) is a unique and innovative pencil-beam scanning system with exceptionally fast energy switching to meet the needs for accurate proton radiation treatment of mobile tumors in the lung and liver. To characterize the detailed radiological physics properties, we have constructed the first complete Monte Carlo treatment head model for HYPERSCAN™ in the TOPAS software and performed experimental validations using dosimetry data.

Methods: A detailed model of the HYPERSCAN™ including energy switching geometry, materials and time-dependent characteristics was constructed in TOPAS. Beam scanning spot sizes in air at several positions in the beam direction for 228 MeV proton beam were measured for initial validation. Spot sizes at the isocenter for 50.6 MeV, 110 MeV, 151.1 MeV, 188.9 MeV, 204 MeV and 228 MeV were also measured to verify the scattering for the various energy configurations. Furthermore, we simulated the integrated depth dose (IDD) that is also measured using a Bragg Peak chamber in a water tank to validate the dosimetric accuracy of the model. We performed proton beam imaging simulations for an anthropomorphic head phantom.

Results: The mean difference between measured data and simulated spot sizes is 0.2±0.2 mm. The differences in IDD between TOPAS simulations and experiment measurements were less than 0.6% at all measured depths.

Conclusion: The results of Monte Carlo simulations agreed closely with the experimental data, thus confirming the accuracy of this Monte Carlo model. On-going work includes the application of this pencil beam scanning treatment system model to the study of image-guided proton treatment of tumor targets that are subject to respiration and the research of proton imaging for In-vivo beam range verification.

Funding Support, Disclosures, and Conflict of Interest: Some of the authors are employed by Mevion Medical Systems, Littleton, MA.

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