Program Information
Energy Dependency of Dose Response Function of An Optical Dosimeter and EDR2 Film for Spot-Scanning Proton and Carbon-Ionbeams
Y Li , Z Huang , W Hsi*, Shanghai Proton and Heavy Ion Center, Shanghai, Shanghai
Presentations
SU-I-GPD-T-150 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: To systematically study energy dependency of dose response function between a gadoliniumsulfoxylate (GdO) optical dosimeter and EDR2 for spot-scanning particle (proton and carbon-ion) beams.
Methods: Before performing the dose response, the non-linear sensitivity of the film scanner and the imager of optical dosimeter are obtained to correct raw-reading to an optic density (OD) for film and a Nominal stimulated-light-emission (N-SLE). Each single energy-layer uniform scanning fields with 5 different dose level are used to irradiate the optical dosimeter and EDR films. The fit slope; as response factor K, for measured OD/N-SLE to doses are obtained for more than 10 different energies for proton and carbon. The trend of K-factor as a function of energy present the Energy dependency of dose response function.
Results: Because the light passing through the darken film is exponential reduction from initial intensity, a standard log-scale Stouffer light step-wedge was used for film. But, because the imager of camera is designed to enhance at a desired intensity, the sensitivity of optical dosimeter presents a power-law trend between raw-reading and N-SLE. After proper sensitivity calibaration, the OD/N-SLE as a function of dose for each energy is linear for both optical dosimeter and film. The K-factor of film varies smaller for proton at energies of 80-250 MeV, but varies significantly for carbon-ion at energies of 80-450 MeV/n. But, much smaller variation of K-factor for optical dosimeter indicates smaller energy-dependency.
Conclusion: Significant reduced energy-dependency of optical dosimeter allow better measuring lateral profiles of scanning fields when the actual energy-dependency may not be able corrected. Also, measurements using optical dosimeter can be real-time analyzed to provide better efficiency during routinely daily and weekly QA than using EDR2 film.
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