Multileaf collimator tongue-and-groove effect on depth and off-axis doses: A comparison of treatment planning data with measurements and Monte Carlo calculations

Hee Jung Kim, Siyong Kim, Yang Kyun Park, Jung In Kim, Jong Min Park, Sung Joon Ye

Research output: Contribution to journalArticle

3 Citations (Scopus)

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 10 cm and also by up to 4.1% with increasing off-axis distances of 0 to 13 cm. 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 0.19 cm for MC and 0.17 cm for RCF, but 0.30 cm for Eclipse TPS and 0.45 cm 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.

Original languageEnglish (US)
Pages (from-to)271-278
Number of pages8
JournalMedical Dosimetry
Volume40
Issue number4
DOIs
StatePublished - Jan 1 2015

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Keywords

  • MLC
  • Monte carlo
  • Tongue-and-groove effect
  • TPS

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Oncology
  • Radiology Nuclear Medicine and imaging

Cite this

Multileaf collimator tongue-and-groove effect on depth and off-axis doses : A comparison of treatment planning data with measurements and Monte Carlo calculations. / Kim, Hee Jung; Kim, Siyong; Park, Yang Kyun; Kim, Jung In; Park, Jong Min; Ye, Sung Joon.

In: Medical Dosimetry, Vol. 40, No. 4, 01.01.2015, p. 271-278.

Research output: Contribution to journalArticle

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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 10 cm and also by up to 4.1{\%} with increasing off-axis distances of 0 to 13 cm. 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 0.19 cm for MC and 0.17 cm for RCF, but 0.30 cm for Eclipse TPS and 0.45 cm 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.",
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