Energy and dose dependence of GafChromic EBT3-V3 film across a wide energy range

Abstract

Aim: To determine the energy and dose dependence of GafChromic EBT3-V3 film over an energy range 0.2 mm Al HVL to 6 MV. Background: The decay scheme of a brachytherapy source may be complex and the spectrum of energy can be wide. LiF TLDs are the golden standard recommended for dosimetric measures in brachytherapy, for their energy independence, but TLDs could be not available in some centres. An alternative way to perform dose measurements is to use GafChromic films, but they show energy dependence. Methods and materials: Films have been irradiated at increasing dose with three different beams: 6 MV beam, TPR20, 10 = (0.684 ± 0.01), HVL = (2.00 ± 0.01)mmAl and HVL = (0.20 ± 0.01)mmAl. Calibration curves were generated using the same dose range (0cGy to 850cGy) for the three energies. Using the 6 MV calibration curve as reference, the film response in terms of net optical density (OD) was evaluated. Results: The difference in the calibration curve obtained by irradiating the film with 6 MV and 2 mm Al HVL energy beams is less than 3 %, within the calibration uncertainty, in the dose range 500-850cGy. The OD of EBT3-V3 film is significantly lower at 0.2 mmAl HVL compared to 6 MV, showing differences up to 25 %. Conclusion: Within the range 6 MV-2 mm Al HVL and dose higher than 500cGy, GafChromic EBT3-V3 films are energy independent. In this dose range, films can be calibrated in a simple geometry, using a 6 MV Linac beam, and can be used for brachytherapy sources dose measures. The use of EBT3 films can be extended to reference dosimetry in Ir-192 clinical brachytherapy.

End-to-end dosimetric audit: A novel procedure developed for Irish HDR brachytherapy centres

“…In order to calibrate GafChromic EBT3-V3 films, an energy independence check was performed as published by Bassi et al [28]. Film was irradiated at increasing doses with three different beams: 6 MV beam from Elekta Precise Linac, TPR 20,10 = 0.684 ± 0.01, HVL = 2.00 ± 0.01 mm Al and HVL = 0.20 ± 0.01 mm Al, from Xstrahl Gulmay Orthovoltage unit.…”

“…Hence, EBT3-V3 films are suitable dose detectors when the dose response curve is measured within the range 6 MV and 2 mm Al HVL. 6 MV calibration curve could be used within this range, with 3%, k = 2, uncertainty [28].…”

Dose Distribution of 192Ir HDR Brachytherapy Source Measurement using Gafchromic® EBT3 Film Dosimeter and TLD-100H

“…Based on the literature, the most frequently reported dosimetry systems in the determination of the dosimetric function of 192 Ir source are film dosimetry and thermoluminescent dosimeter (TLD) (Ayoobian et al, 2016;Bassi et al, 2020;DeWerd et al, 2014;Sellakumar et al, 2009;Uniyal et al, 2011;Wu et al, 2014). The dosimetric functions of 192 Ir studied by Sellakumar et al (2009) were measured the Λ , , and F(r, θ) for HDR 192 Ir source using Gafchromic® EBT films.…”

“…A recent study by Bassi et al (2020) reported, EBT3 film was energy independent and can be utilised for brachytherapy source dose monitoring despite being calibrated with a 6MV photon beam and could be expanded to be applied in clinical dosimetry brachytherapy. Besides film dosimetry, TLDs also was recommended for dosimetric measurement in brachytherapy because of their excellent sensitivity, miniature, flat energy response, and energy independence.…”

“…Previously, dosimetry protocols or a set of dosimetry procedures employing film dosimetry and TLD had been published (Ayoobian et al, 2016;Bassi et al, 2020;Faghihi & Street, 2015;Palmer et al, 2013;Sellakumar et al, 2009). However, they reported the properties of Gafchromic EBT, EBT2 and TLD 100 in their study.…”