Fast and accurate sensitivity analysis of IMPT treatment plans using Polynomial Chaos Expansion

Zoltá Perkó, Sebastian R. Van Der Voort, Steven Van De Water, Charlotte M.H. Hartman, Mischa Hoogeman, Danny Lathouwers

Research output: Contribution to journalArticleScientificpeer-review

16 Citations (Scopus)
45 Downloads (Pure)

Abstract

The highly conformal planned dose distribution achievable in intensity modulated proton therapy (IMPT) can severely be compromised by uncertainties in patient setup and proton range. While several robust optimization approaches have been presented to address this issue, appropriate methods to accurately estimate the robustness of treatment plans are still lacking. To fill this gap we present Polynomial Chaos Expansion (PCE) techniques which are easily applicable and create a meta-model of the dose engine by approximating the dose in every voxel with multidimensional polynomials. This Polynomial Chaos (PC) model can be built in an automated fashion relatively cheaply and subsequently it can be used to perform comprehensive robustness analysis. We adapted PC to provide among others the expected dose, the dose variance, accurate probability distribution of dose-volume histogram (DVH) metrics (e.g. minimum tumor or maximum organ dose), exact bandwidths of DVHs, and to separate the effects of random and systematic errors. We present the outcome of our verification experiments based on 6 head-and-neck (HN) patients, and exemplify the usefulness of PCE by comparing a robust and a non-robust treatment plan for a selected HN case. The results suggest that PCE is highly valuable for both research and clinical applications.

Original languageEnglish
Pages (from-to)4646-4664
JournalPhysics in Medicine and Biology
Volume61
Issue number12
DOIs
Publication statusPublished - 2016

Keywords

  • Polynomial Chaos
  • proton therapy
  • Range error
  • Robust optimization
  • Sensitivity
  • Setup error
  • Uncertainty

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