Program Information
Evaluation of Gafchromic EBT-XD Film Using Vidar DosimetryPRO Advantage Red Scanner for SRS and SBRT QA
M Dumas*, N Wen , Henry Ford Health System, Detroit, MI
Presentations
TU-C2-GePD-TT-3 (Tuesday, August 1, 2017) 10:00 AM - 10:30 AM Room: Therapy ePoster Theater
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 25Gy with 18x18 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 15x15 cm2 and a 5x5 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 10Gy and 27% at 24Gy. Non-uniformity of EBT-XD film stays constant and does not go above 1.1% in the 3Gy to 25Gy range. The mean EBT-XD film non-uniformity for the 15x15 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 15-27Gy. EBT-XD film has no discernible energy dependence between 6MV FFF and 10MV FFF photon energies.
Conclusion: EBT-3 film shows superior sensitivity compared to the EBT-XD. The EBT-XD non-uniformity was shown to be below 1.2% for conventional radiotherapy doses up to SRS doses of 25Gy for EBT-XD and EBT-3 film, therefore both films are acceptable for SBRT/SRS QA.
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