Measurement and verification on DMLC physical parameters of Varian medical linac accelerator
Author(s): LI Jun, ZHANG Xizhi, ZHANG Xianwen, CHEN Xuemei, GUI Longgang, TANG Xiaobin, CHAI Lei, CHEN Da
Pages: 509-513
Year: 2015 Issue: 5
Journal: Beijing Biomedical Engineering
Keyword: accelerator; physical parameter; measurement; verification;
Abstract: Objective To measure the parameters of dynamic multileaf collimator ( DMLC ) including leaf transmission factor, between?leaf leakage factor, leaf position correction factor, inner and outer penumbra for 60 pairs of leaves in Varian IX medical linac accelerator and 40 in Varian 23 EX, respectively, to analyze the effects of X?ray energy and leaf numbers on the DLMC parameters, whose importance is also analyzed in treatment planning system ( TPS)? Methods The five parameters of DLMC:leaf transmission factor, between?leaf leakage factor, leaf position correction factor, inner and outer penumbra are measured, and the results are imported into TPS? The inverse intensity?modulated radiation therapy ( IMRT) is designed for phantom in TPS, and the phantom with a film is irradiated on the accelerator couch, then the dose distribution is comparatively analyzed between the measured results on the film and TPS? Results As to the same number of DMLC leaves, the higher the X?ray energy, the bigger the parameters? As to the same X?ray energy, the more the DMLC leaves, the bigger the parameters? The area contact ratios of 80%isodose line got from both actual measurement on the film and TPS are higher than 95%, and the separation degree of the curves are both lower than 3 mm? Conclusions Although each DMLC parameter can be influenced by the leaf number and X?ray energy, the dose distributions of both actual measurement and TPS are capable of satisfying higher contact ratio and lower separation degree by guiding the measured DMLC parameters into TPS, which meet the clinical application requirement.
Pages: 509-513
Year: 2015 Issue: 5
Journal: Beijing Biomedical Engineering
Keyword: accelerator; physical parameter; measurement; verification;
Abstract: Objective To measure the parameters of dynamic multileaf collimator ( DMLC ) including leaf transmission factor, between?leaf leakage factor, leaf position correction factor, inner and outer penumbra for 60 pairs of leaves in Varian IX medical linac accelerator and 40 in Varian 23 EX, respectively, to analyze the effects of X?ray energy and leaf numbers on the DLMC parameters, whose importance is also analyzed in treatment planning system ( TPS)? Methods The five parameters of DLMC:leaf transmission factor, between?leaf leakage factor, leaf position correction factor, inner and outer penumbra are measured, and the results are imported into TPS? The inverse intensity?modulated radiation therapy ( IMRT) is designed for phantom in TPS, and the phantom with a film is irradiated on the accelerator couch, then the dose distribution is comparatively analyzed between the measured results on the film and TPS? Results As to the same number of DMLC leaves, the higher the X?ray energy, the bigger the parameters? As to the same X?ray energy, the more the DMLC leaves, the bigger the parameters? The area contact ratios of 80%isodose line got from both actual measurement on the film and TPS are higher than 95%, and the separation degree of the curves are both lower than 3 mm? Conclusions Although each DMLC parameter can be influenced by the leaf number and X?ray energy, the dose distributions of both actual measurement and TPS are capable of satisfying higher contact ratio and lower separation degree by guiding the measured DMLC parameters into TPS, which meet the clinical application requirement.
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