Room: ePoster Forums
Purpose: Gafchromicâ„¢ EBT3 film is a widely used dosimeter for research as well as clinical applications. The composition of the film can vary from batch to batch. The primary objective of this study was to assess the consistency in the dose response curve of the EBT3 film for several batches using two beam qualities.
Methods: Three batches of EBT3 films (lot dates: 2017, 2018, and 2019) were irradiated to known doses using a Cobalt-60 and a NIST-matched M40 x ray beam (effective energy: 19.8 keV). A total of sixty films (1.2 cm x 1.2 cm) were irradiated to six different dose to water values ranging from 0.5 Gy to 7 Gy using the two beam qualities. A flatbed scanner was used for readout, and a custom software code was used for analysis. NIST-traceable optical density filters were scanned together with the films to minimize inter-scan variations.
Results: The difference in the measured net optical density of the 2017 lot compared to the 2018 lot ranged from -1% to -16% for the Cobalt-60 beam for different dose levels and -6% to -18% for the M40 x ray beam. Differences ranging from 1% to 25% for the Cobalt-60 beam and 2% to 26% for the M40 x ray beam were observed when comparing the measured net optical densities for the 2019 and 2018 lots. The ratio of net optical density measured using the M40 x ray and Cobalt-60 beams ranged from 0.92-1.08, 0.97-0.99, and 0.97-0.99 for 2017, 2018 and 2019 lots respectively for all dose values.
Conclusion: The dosimetric response of the EBT3 film varied for three different batches that were used for this work indicating compositional variations of the film. A calibration curve should be ascertained for each batch of film when used for a dose measurement.