title: Multileaf collimator tongue-and-groove effect on depth and off-axis doses: a comparison of treatment planning data with measurements and Monte Carlo calculations.
abstract: To investigate how accurately treatment planning systems (TPSs) account for the tongue-and-groove (TG) effect, Monte Carlo (MC) simulations and radiochromic film (RCF) measurements were performed for comparison with TPS results. Two commercial TPSs computed the TG effect for Varian Millennium 120 multileaf collimator (MLC). The TG effect on off-axis dose profile at 3 depths of solid water was estimated as the maximum depth and the full width at half maximum (FWHM) of the dose dip at an interleaf position. When compared with the off-axis dose of open field, the maximum depth of the dose dip for MC and RCF ranged from 10.1% to 20.6%; the maximum depth of the dose dip gradually decreased by up to 8.7% with increasing depths of 1.5 to 10cm and also by up to 4.1% with increasing off-axis distances of 0 to 13cm. However, TPS results showed at most a 2.7% decrease for the same depth range and a negligible variation for the same off-axis distances. The FWHM of the dose dip was approximately 0.19cm for MC and 0.17cm for RCF, but 0.30cm for Eclipse TPS and 0.45cm for Pinnacle TPS. Accordingly, the integrated value of TG dose dip for TPS was larger than that for MC and RCF and almost invariant along the depths and off-axis distances. We concluded that the TG dependence on depth and off-axis doses shown in the MC and RCF results could not be appropriately modeled by the TPS versions in this study.
authors: Interdisciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, Korea; Department of Biomedical Engineering, Seoul National University, Seoul, Korea; Department of Radiation Oncology, Soonchunhyang University Hospital, Seoul, Korea.
authors: Hee Jung
authors: HJ
authors: Kim
authors: Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA.
authors: Siyong
authors: S
authors: Kim
authors: Interdisciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, Korea; Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA, USA.
authors: Yang-Kyun
authors: YK
authors: Park
authors: Interdisciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, Korea; Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.
authors: Jung-In
authors: JI
authors: Kim
authors: Interdisciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, Korea; Department of Transdisciplinary Studies, Seoul National University, Seoul, Korea.
authors: Jong Min
authors: JM
authors: Park
authors: Interdisciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, Korea; Department of Transdisciplinary Studies, Seoul National University, Seoul, Korea; Advanced Institutes of Convergence Technology, Seoul National University, Suwon, Korea. Electronic address: sye@snu.ac.kr.
authors: Sung-Joon
authors: SJ
authors: Ye
mesh_terms: D006801:Humans; D008962:Models, Theoretical; D009010:Monte Carlo Method; D011880:Radiotherapy Planning, Computer-Assisted
keywords: MLC; Monte Carlo; TPS; Tongue-and-groove effect