Dynamic fluence map sequencing using piecewise linear leaf position functions

Matthew Kelly, Jacobus H. M. van Amerongen, Marleen Balvert, David Craft*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Within the setting of intensity modulated radiation therapy (IMRT) and the fully continuous version of IMRT called volumetric modulated radiation therapy (VMAT), we consider the problem of matching a given fluence map as well as possible in limited time by the use of a linear accelerator (linac) with a multi-leaf collimator (MLC). We introduce two modeling strategies to manage the nonconvexity and the associated local minima of this problem. The first is the use of linear splines to model the MLC leaf positions as functions of time. The second is a progressively controllable smooth model (instead of a step function) of how the leaves block the fluence radiation. We propose a two part solution: an outer loop that optimizes the dose rate pattern over time, and an inner loop that given a dose rate pattern optimizes the leaf trajectories.
Original languageEnglish
Article number025036
Number of pages11
JournalBiomedical physics & engineering express
Issue number2
Publication statusPublished - Feb 2019


  • MLC
  • optimization
  • fluence map
  • sliding window
  • VMAT
  • IMRT


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