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SU‐E‐T‐560: The Use of EBT2 Films for IPlan Commissioning Verification
Author(s) -
Chan M,
Zhang Q,
Li J,
Schupak K,
Burman C
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3612522
Subject(s) - materials science , dosimetry , calibration , scanner , linear particle accelerator , irradiation , nuclear medicine , calibration curve , optics , beam (structure) , physics , medicine , nuclear physics , mathematics , statistics , quantum mechanics , detection limit
Purpose: To evaluate the measured dose distributions using radiochromic EBT2 films for small fields in iPlan (BrainLab) commissioning. Methods: Radiochromic EBT2 films were irradiated with 6MV photons on a Varian Trilogy linac using polystyrene phantoms. The measurements included dose profiles and depth doses for field sizes of 1×1, 2×2, 3×3, 4×4, and 10×10cm2 etc. The dose profile measurements were taken at the depth of 5cm. The calibration films were irradiated at dmax (1.4cm) for doses up to 6 Gy. Films were scanned using an Epson 10000XL flatbed scanner with 72 dpi resolution. Pixel values were converted to doses using the established calibration‐curve. The 2D dose distributions were generated from the film data analysis. In‐house software was utilized to compare the measured doses from films with the associated treatment planing data. In addition, sample patientsˈ SRS plans were also measured with the EBT2 films for comparison with iPlan. MapCHECK was also used to check the central‐axis doses for the SRS patientsˈ measurements. Results: The measured planar dose distributions achieved more than 95% passing rates with a set of 2%/2mm dose and DTA criteria for all patient treatment fields (< 5×5cm2). Agreement with measurement data with MapCHECK at the central axis (+1%) was found with the plan data. This is the first report for SRS small photon‐field measurements using the latest radiochromic film, EBT2. The results shown in this work indicate that the use EBT2 film provides accurate dosimetry measurements for small photon beams. The measurements show excellent agreement with validated small ion chamber measurements data that were entered into iPlan as commissioning data. Conclusions: The patient‐specific EBT2 film QA for iPlan SRS patients showed good results. The EBT2 films could potentially be a useful dosimeter in verification of commissioning as well as patient‐specific QA for SRS cases.