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Evaluation of EBT2 and EBT3 Films for Dosimetry in Laser-Driven Ion Accelerators

K Parodi

S Reinhardt1, M Hillbrand2, J Wilkens3, W Assmann1, K Parodi1*, (1) Faculty of Physics, Ludwig-Maximilians University Munich, Garching, Germany,(2) Rinecker Proton Therapy Center, Munich, Germany, (3) Department of Radiation Oncology, Technical University Munich, Klinikum rechts der Isar, Munich, Germany,

SU-E-T-52 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:Laser-driven ion accelerators could be a future option for a compact medical ion accelerator for radiation therapy. Laser ion accelerators can deliver a typical dose of few Gy in a single ion pulse of ns duration. Their dose rate, thus, exceeds the typical dose rate of a medical accelerator by several orders of magnitude. Dosimetry at high repetition rate laser ion accelerators requires 2D dosimeters with dose-rate independent response. Both requirements can be fulfilled by Gafchromic EBT2 or EBT3 films. Energies for application of laser accelerated ions (e.g. in cell irradiation experiments) are still limited to about 10 MeV. Dose response and energy dependence of Gafchromic EBT2 or EBT3 films are, therefore, evaluated in the low proton energy regime as delivered by a laser ion accelerator and compared to clinical photon and proton beams.

Methods:The dose response of EBT2 and EBT3 film has been characterized for a wide proton energy range. 6 MV photon irradiations at a clinical Linac provide a reference curve. The energy dependence of both films, has been studied in particular for low proton energies as predominating in the vicinity of the Bragg peak. Mono-energetic beams of 3 MeV, 11 MeV and 20 MeV but also up to a maximum energy of 200 MeV were used for these studies.

Results:In general, EBT2 and EBT3 have a comparable performance and show similar response to photons and protons down to a proton energy of 10 MeV. A dose under-estimation by up to 20 % in the Bragg peak region is visible in depth dose measurements of both types of film.

Conclusion:EBT 2 and EBT3 films can be applied as 2D dosimeter in the low proton energy regime of a laser ion accelerator. Dose under-response corrections are required for proton energies below 10 MeV.

Funding Support, Disclosures, and Conflict of Interest: This work was funded by the DFG cluster of excellence Munich Centre for Advanced Photonics (MAP).

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