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Evaluation of Dual-Channel Compound Method On EBT3 Film Dosimetry for Stereotactic Body Radiotherapy Quality Assurance

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J Chung

J Chung1*, S Kang2 , T Suh2 , W Cho3 , J Lee4 , (1) Seoul National University Bundang Hospital, Seongnam, Kyeonggi-do, (2) The Catholic University of Korea, Seoul, (3) SMG-Seoul National University Boramae Medical Center, Seoul, (4) Konkuk University Medical Center, Seoul,


SU-I-GPD-T-231 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The aim of this study is to investigate the feasibility of the dual-channel (DC) compound method on EBT film dosimetry for stereotactic body radiotherapy quality assurance (SBRT-QA).

Methods: Prior to perform the dosimetry, film calibration was performed in doses ranging from 0 to 15 Gy with 6-MV photon beams at the 10 × 10 cm² field. The net optical density was obtained with the measured film for each color channel. To compare the red channel (RC) and green channel (GC) for various dose ranges, the dose distribution was generated in treatment planning system and measured in film for a 6-MV photon beam of 10 × 20 cm² field with 60° dynamic-wedge. The calculated and measured dose distributions were evaluated with root-mean-squares-error (RMSE) and gamma analysis. With the gamma analysis using RC and GC, the DC compound method was made based on the RC after correcting the GC for high doses to exclude the uncertainty in each channel. Pretreatment quality assurance was performed on 3 plans for stereotactic body radiotherapy, and gamma passing rates are presented for each channel.

Results: For RMSE value of each channel, the RC is more accurate than GC for low doses while the GC is more accurate in higher doses than 8 Gy. For the gamma passing rates with 3%/3 mm criteria in the whole dose range, all plans for each channel met agreement more than 94%. However the mean passing rate (98.8%) of DC compound method was the highest when comparing with single channel method such as the RC (97.4%) and GC (97.1%).

Conclusion: This study found that the use of DC compound method is more appropriate as the dosimetric QA using EBT3 film for SBRT.

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