Radiochromic film dosimetry: considerations on precision and accuracy for EBT2 and EBT3 type films

Ralf Dreindl; Dietmar Georg; Markus Stock

doi:10.1016/j.zemedi.2013.08.002

Radiochromic film dosimetry: considerations on precision and accuracy for EBT2 and EBT3 type films

Z Med Phys. 2014 May;24(2):153-63. doi: 10.1016/j.zemedi.2013.08.002. Epub 2013 Sep 20.

Authors

Ralf Dreindl¹, Dietmar Georg², Markus Stock³

Affiliations

¹ Department of Radiooncology, Comprehensive Cancer Center, Medical University of Vienna/Vienna General Hospital; EBG MedAustron GmbH, Marie-Curie-Straße 5, 2700 Wiener Neustadt, Austria.
² Department of Radiooncology, Comprehensive Cancer Center, Medical University of Vienna/Vienna General Hospital; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna.
³ Department of Radiooncology, Comprehensive Cancer Center, Medical University of Vienna/Vienna General Hospital; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna. Electronic address: markus.stock@akhwien.at.

PMID: 24055395
DOI: 10.1016/j.zemedi.2013.08.002

Abstract

Gafchromic® EBT2 film is a widely used dosimetric tool for quality assurance in radiation therapy. In 2012 EBT3 was presented as a replacement for EBT2 films. The symmetric structure of EBT3 films to reduce face-up/down dependency as well as the inclusion of a matte film surface to frustrate Newton Ring artifacts present the most prominent improvements of EBT3 films. The aim of this study was to investigate the characteristics of EBT3 films, to benchmark the films against the known EBT2-features and to evaluate the dosimetric behavior over a time period greater than 6 months. All films were irradiated to clinical photon beams (6 MV, 10 MV and 18 MV) on an Elekta Synergy Linac equipped with a Beam Modulator MLC in solid water phantom slabs. Film digitalization was done with a flatbed transparency scanner (Type Epson Expression 1680 Pro). MATLAB® was used for further statistical calculations and image processing. The investigations on post-irradiation darkening, film orientation, film uniformity and energy dependency resulted in negligible differences between EBT2 and EBT3 film. A minimal improvement in face-up/down dependence was found for EBT3. The matte film surface of EBT3 films turned out to be a practical feature as Newton rings could be eliminated completely. Considering long-term behavior (> 6 months) a shift of the calibration curve for EBT2 and EBT3 films due to changes in the dynamic response of the active component was observed. In conclusion, the new EBT3 film yields comparable results to its predecessor EBT2. The general advantages of radiochromic film dosimeters are completed by high film homogeneity, low energy dependence for the observed energy range and a minimized face-up/down dependence. EBT2 dosimetry-protocols can also be used for EBT3 films, but the inclusion of periodical recalibration-interval (e.g. once a quarter) is recommended for protocols of both film generations.

Keywords: EBT2; EBT3; Eigenschaften; Film dosimetry; Filmdosimetrie; Langzeit-Effekte; characterization; long-term effects.

Publication types

Comparative Study
Evaluation Study
Research Support, Non-U.S. Gov't

MeSH terms

Dose-Response Relationship, Radiation
Equipment Design
Equipment Failure Analysis
Film Dosimetry / instrumentation*
Film Dosimetry / methods*
Radiation Dosage*
Reproducibility of Results
Sensitivity and Specificity