SU-E-T-118: Characterization of EBT3 Films in Photon and Proton Beams.

To measure the calibration curves of EBT3 dosimetry films in photon and proton beams and to quantify the related uncertainties from one beam type to another. EBT3 Gafchromic films have similar properties than EBT2 with a symmetric construction and a matte polyester substrate to prevent Newton's ring artefacts. Films from a same batch were exposed in three different beam qualities, an Elekta SL25 6 MV photon beam, a 100 MeV 5×5cm2 proton beam delivered by pencil-beam scanning dedicated system from IBA and a 60 MeV fixed proton beam (2.5cm in diameter) at Clatterbridge Center for Oncology (CCO), UK. The films were read using an EPSON 10000 XL/PRO scanner. Film calibration curves were acquired for all modalities within a range of 0.05 to 20 Gy. Influence of increasing linear-energy transfer (LET) on film response was investigated by comparing dose measured by EBT3 to a silicon diode detector in depth for a fully-modulated beam using the CCO beam line (homogeneous dose with distal end at 3.1cm in water). A comprehensive uncertainty budget (reproducibility, uniformity'¦) was estimated on films irradiated by Elekta SL25. The main source of uncertainty was the non-uniformity of the scanner response. By placing all the irradiated films at the center of the scanner, the uncertainty could be reduced from 5.8% to 1.9% (1 sigma). For all beams and energies, the calibration curves were matched within uncertainties. Along the fully-modulated depth dose curve, diode and EBT3 measurement were in a 4% agreement point-to-point, indicating films weak dependence with LET. The weak influence of LET, beam type and energy on film response as well as its small uncertainty make EBT3 suitable for relative dosimetry and a promising candidate for measuring correction factors (quality, recombination,'¦) for reference dosimetry with ion chambers of non-standard beams (e.g pencil-beam scanning proton-therapy). “This work is supported by the Walloon Region under the project name InVivoIGT, convention number 1017266.â€.

Sorriaux J ，Rossomme S ，Kacperek A ，Bertrand D ，Vynckier S ，Sterpin E ... -  《-》

Evaluation of Gafchromic® EBT3 films characteristics in therapy photon, electron and proton beams.

To evaluate the uncertainties and characteristics of radiochromic film-based dosimetry system using the EBT3 model Gafchromic(®) film in therapy photon, electron and proton beams. EBT3 films were read using an EPSON Expression 10000XL/PRO scanner. They were irradiated in five beams, an Elekta SL25 6 MV and 18 MV photon beam, an IBA 100 MeV 5 × 5 cm(2) proton beam delivered by pencil-beam scanning, a 60 MeV fixed proton beam and an Elekta SL25 6 MeV electron beam. Reference dosimetry was performed using a FC65-G chamber (Elekta beam), a PPC05 (IBA beam) and both Markus 1916 and PPC40 Roos ion-chambers (60 MeV proton beam). Calibration curves of the radiochromic film dosimetry system were acquired and compared within a dose range of 0.4-10 Gy. An uncertainty budget was estimated on films irradiated by Elekta SL25 by measuring intra-film and inter-film reproducibility and uniformity; scanner uniformity and reproducibility; room light and film reading delay influences. The global uncertainty on acquired optical densities was within 0.55% and could be reduced to 0.1% by placing films consistently at the center of the scanner. For all beam types, the calibration curves are within uncertainties of measured dose and optical densities. The total uncertainties on calibration curve due to film reading and fitting were within 1.5% for photon and proton beams. For electrons, the uncertainty was within 2% for dose superior to 0.8 Gy. The low combined uncertainty observed and low beam and energy-dependence make EBT3 suitable for dosimetry in various applications.

Sorriaux J ，Kacperek A ，Rossomme S ，Lee JA ，Bertrand D ，Vynckier S ，Sterpin E ... -  《-》

Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and (60)Co γ-rays.

Vadrucci M ，Esposito G ，Ronsivalle C ，Cherubini R ，Marracino F ，Montereali RM ，Picardi L ，Piccinini M ，Pimpinella M ，Vincenti MA ，De Angelis C ... -  《-》

SU-E-T-128: Dosimetric Characteristics of Gafchromic EBT3 Films for Megavoltage Photon and Proton Beams.

Gafchromic film for quantitative analysis was renewed from EBT2 to EBT3 film in November 2011. The purpose of this study is to investigate the relevant characteristics of EBT3 film for its application in dosimetric verification for IMRT/VMAT or proton therapy. We investigated the characteristics of EBT3 film with comparison of previous EBT2 film. The experiments in this study composed two categories. At first, the photo spectroscopy for the irradiated film was compared between EBT2 and EBT3. The film 1 day after the irradiation was analyzed by a photo spectrometer (SR520: JASCO Corporation, Japan). Secondly, we investigated several calibration curves which obtained by same batch. The films were calibrated by irradiation the films to 13 dose steps. The irradiated films were scanned by a flatbed scanner (ES-10000XL, Epson-Seiko Corporation, Japan). The difference on scan orientation was evaluated alternate portrait and landscape directions. The photon and proton beams were delivered from Clinac 21EX (Varian) and Mitsubishi machine, respectively. The peak absorption wavelength of EBT3 film and its response at all active range were basically same with that of EBT2 film. The peak wavelength of photo absorption in EBT3 was observed at 585 and 634 nm. The fog optical density was increased due to the hazy matte polyester for active layer. However, there is no change the tendency of the calibration curve responding to megavoltage photon and proton beams. The scan orientation dependency of EBT3 film was observed with similar to EBT2 film. The optical density of portrait orientation was 10% higher than that of landscape orientation. The dosimetric characteristics of EBT3 film were basically same with EBT2 film. With regard to the matte polyester, the creation of Newton's rings during scanning procedure was reduced. However, the suitable scan protocol should be used for accurate film dosimetry.

Hayashi N ，Kato H ，Yada R ，Matsunaga T ，Ehara I ，Adachi Y ... -  《-》

LET response variability of Gafchromic TM EBT3 film from a 60 Co calibration in clinical proton beam qualities.

Smith BR ，Pankuch M ，Hammer CG ，DeWerd LA ，Culberson WS ... -  《-》