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SU‐E‐T‐126: IMRT and Rapid Arc Commissioning of Truebeam Linear Accelerator Using Gafchromic EBT3 Film
Author(s) -
Wen N,
Zhao B,
Barton K,
Chin K,
Kim J,
Liu C,
Chetty I
Publication year - 2013
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 - 10.1118/1.4814561
Subject(s) - truebeam , nuclear medicine , cls upper limits , medicine , confidence interval , dosimetry , imaging phantom , ionization chamber , dose profile , linear particle accelerator , physics , optics , ion , beam (structure) , quantum mechanics , optometry , ionization
Purpose: The study is to establish confidence limits (CLs) for both IMRT and RapidArc (RA) of all five photon energies (6X, 10X, 15X, 6XFFF, 10XFFF) of a TrueBeam system based on TG119 Guideline. Methods: Both IMRT and RA plans were created in solid water phantom. The test plans were representative of normal clinical treatment sites including AP/PA fields, bands, multiple target, prostate, head & neck, easy and hard C‐shape. A high dose point in the PTV and a low dose point in the critical organ were measured with ion chamber. The percentage difference was defined as [(measured dose — plan dose)/Prescription dose]. Planar dose distributions were also measured in the high and low dose regions with EBT3 films. The confidence limit was set to have 95% of the measured data fall within the tolerance. It was defined as (mean + 1.96 σ) for point dose measurement and [(100‐mean) + 1.96 σ] for passing gamma criteria of 3%/3mm. Results: The CLs of high dose point in the target were 0.031 (range, 0.024 — 0.038) in the IMRT plans and 0.031 (range, 0.016 — 0.043) in the RA plans. The CLs of low point dose in the avoidance structures were 0.028 (range, 0.024 —0.039) in the IMRT plans and 0.029 (range, 0.017 — 0.047) in the RA plans. The CLs of passing 3%/3mm gamma criteria in the high dose region were 6.28 (range, 1.4 — 8.6) in the IMRT plans and 4.84 (range, 1.5 — 8.8) in the RA plans. The CLs in the low dose region were 5.04 (range, 1.2 — 7.4) and 4.2 (range, 1.8 — 8.3) in the IMRT plans. Conclusion: We have established the CLs values to access the overall accuracy to ensure the high precision of IMRT and RA delivery. They were all within the values published in TG1 19.