Comprehensive Evaluation in the Use of Gafchromic EBT3 Film for High-Dose Radiation Therapy
K Liu1*, P Jorge2, R Moeckli2, E Schueler1, (1) MD Anderson Cancer Center, Houston, TX, (2) Institute of Radiation Physics, Lausanne, VD, CH,
Presentations
TU-F115-IePD-F4-4 (Tuesday, 7/12/2022) 1:15 PM - 1:45 PM [Eastern Time (GMT-4)]
Exhibit Hall | Forum 4
Purpose: In this study, we evaluated Gafchromic film over short- and long-term periods post-irradiation to establish new guidelines in film handling and analysis for robust film dosimetry to address issues related to film dosimetry such as delayed read-out and time-consuming calibration.
Methods: EBT3 films were irradiated using 16 MeV electrons at a dose range of 0-40 Gy with netOD measured using a flatbed scanner. EBT3 was were scanned at timepoints ranging from 5 min–100 hours and up to a year post-irradiation to track changes in their netOD. Films irradiated to the same dose level but scanned with different scanner types were also evaluated to quantify scanner dependence of film. Comparison of 14 batches of film calibration curves over a 5-year period was evaluated using the coefficient of variation in film netOD irradiated from 0.5 – 50 Gy.
Results: Scanning the film within an 8h window of a 24h calibration curve introduced a maximum error of 3% over a dose range of 1-40 Gy, with lower doses showing higher uncertainty. Relative dose measurements, normalized PDDs, demonstrate a less than 2mm difference in electron beam parameters such as R30, R50, R80, and R90 when scanned on different scanners or timepoints with the same calibration curve applied. Analysis of film taken over a period of 5 years show that red channel has the lowest variation in the measured netOD values for different film batches with higher doses (>10 Gy) having the lowest coefficient of variation (<2%).
Conclusion: This study is the first to comprehensively evaluate the temporal dependence of Gafchromic EBT3 film post-irradiation and evaluate the historical difference in calibration curves measured over a five-year period. Relative dosimetric measurements were unaffected when the same calibration curves were applied regardless of scanner and time scanned. New conversions for easy film handling are proposed.
Keywords
Radiochromic Film, Radiation Dosimetry, Dosimetry Protocols
Taxonomy
TH- Radiation Dose Measurement Devices: Radiochromic film
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