Evaluation of gafchromic EBT-XD film using vidar dosimetrypro advantage red scanner for SRS and SBRT QA.

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Conference Proceeding

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Med Phys


Purpose: To characterize the dosimetric non-uniformity, sensitivity, photon energy response, and temporal optical density changes associated with Gafchromic EBT-XD film using the Vidar DosimetryPRO Advantage (Red) scanner, while comparing it to Gafchromic EBT-3 film. Methods: Twelve EBT-XD films were irradiated at four different dose levels between 3 and 25 Gy with 18 × 18 cm2 open fields. Film non-uniformity correction maps were created by: registering and subtracting the Eclipse dose maps from the film dose profile and taking the standard deviation pixel by pixel in the film stack for each dose level. Non-uniformity was calculated at ROIs of 15 × 15 cm2 and a 5 × 5 cm2 to account for conventional or stereotactic sized targets. Dose calibration and sensitivity curves were calculated using in house developed QA software. Dose calibration curves were fitted to a 3rd degree polynomial. The first derivative of the OD calibration curves was taken to determine the scanner's sensitivity per dose delivered (OD/Gy). Film energy dependence was studied for 6MV FFF and 10MV FFF energies. Temporal response was tested by scanning the film at multiple time intervals. Results: Dose sensitivity of EBT-3 was 33% greater than EBT-XD at 10 Gy and 27% at 24 Gy. Non-uniformity of EBT-XD film stays constant and does not go above 1.1% in the 3 Gy to 25 Gy range. The mean EBT-XD film non-uniformity for the 15 × 15 cm2 ROI over the tested dose ranges was 0.76%. EBT-XD film's OD increased by 2% from 14 hr to 48 hr in dose range 15-27 Gy. EBT-XD film has no discernible energy dependence between 6 MV FFF and 10 MV FFF photon energies. Conclusion: EBT-3 film shows superior sensitivity compared to the EBTXD. The EBT-XD non-uniformity was shown to be below 1.2% for conventional radiotherapy doses up to SRS doses of 25 Gy for EBT-XD and EBT-3 film, therefore both films are acceptable for SBRT/SRS QA.





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