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Dose Response Analysis of the Optical Dosimeter Image Data for Modulated-Scanning Ion Beams

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L Sun

L Sun1*, W Hu2 , W Hsi3 , (1) Fudan University Shanghai Cancer Center, Shanghai, Shanghai, (2) Fudan University Shanghai Cancer Center, Shanghai, ,(3) Shanghai Proton and Heavy Ion Center, Shanghai, China,


SU-H3-GePD-J(B)-4 (Sunday, July 30, 2017) 4:00 PM - 4:30 PM Room: Joint Imaging-Therapy ePoster Lounge - B

Purpose: To present availability analysis of an optical dosimeter image data response for modulated-scanning carbon-ion and proton beams during the routine quality assurance of the Siemens IONTRIS system.

Methods: An optical dosimeter using phosphor scintillation was developed to map and interactively analyze the shapes and sizes of spots for a Siemens modulated-scanning system. The pixel dose response to proton & carbon ion had been calibrated first.The dose response was further studied at 0.5cm depth of using uniform 10 cm square field of 6 different energy levels carbon-ion beams proton beams at IONTRIS system. Phosphor scintillation screen of the optical dosimeter was at the isocenter of these beams and at each energy level 7 different dose levels was delivered to the isocenter on the screen, after that all of visible fluorescence were collected by the DSLR camera to generate raw data file for each beam. ImageJ processing software was performed to get the visible fluorescence gray scale value.Analyze the data value and find out dose response curve to evaluate this system.

Results: Similar dose responses were observed for high and low energy carbon ion and proton beams. When the DSLR device measurement condition was lens aperture3.5 and ISO100, the mean gray scale values of 0.25Gyto5Gy for each carbon Ion energy levels were from 8987.25 to 62313.41, and for each proton energy levels were from 3243.91 to 45754.16 respectively. The variation of gray scale values was within approximate linear relationship for both proton beams and carbon ion beams.

Conclusion: During the routine QA of a modulated-scanning ion beam facility, the optical dosimeter could efficiently measure the dose response below 5Gy and substantial no obvious energy dependence for different energy levels. So this device could become a replacement of the traditional film exposure method for dose response measurement in facility quality control workflow.

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