Geometrical analysis for motion monitoring of rigid bodies with optical surface scanning in radiation oncology

Janita Dekker*, Teun Pieter van Wagenberg, Mariska de Smet, Marion Essers, Martijn Kusters, Willy de Kruijf

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Background and purpose: Surface guided radiotherapy can be used to improve patient setup and for accurate intra-fraction motion monitoring in correspondence to the isocenter. For a clinical relevant motion analysis the actual displacement of the entire clinical target volume (CTV) is necessary. Therefore, the aim of this study was to develop a novel assessment method for intra-fraction motion for rigid body structures based on motion data and a geometrical analysis.

Materials and methods: A threshold value on the volume coverage (VC(t)) of the CTV by the planning target volume (PTV) was proposed as online motion monitoring method. Moreover, offline analysis was performed by using heat maps and by calculating VCx, the volume coverage for at least x% of treatment time. The method was applied retrospectively to patient treatment data for whole brain radiation treatment without a thermoplastic mask.

Results: In 132 out of 142 fractions in total the proportion of the CTV that was inside the PTV for at least 99% of the time (VC99) was more than 95%, for a CTV-to-PTV margin of 5 mm. The source-voxel heat map showed which part of the CTV had a reduced coverage and the target heat map showed the movement of the CTV.

Conclusion: Instead of using an action threshold on the movements of the isocenter, a threshold on the VC(t) of the CTV by the PTV was proposed. The heat maps and resulting values of VCx can be used to adapt the VC(t) threshold or the CTV-to-PTV margin for subsequent fractions.

Original languageEnglish
Pages (from-to)105-110
Number of pages6
JournalPhysics & Imaging in Radiation Oncology
Volume20
DOIs
Publication statusPublished - Oct 2021
Externally publishedYes

Keywords

  • BREATH-HOLD
  • INTRAFRACTION MOTION
  • Intra-fraction motion monitoring
  • Isocenter movement
  • RADIOTHERAPY
  • Rigid body
  • SETUP
  • SYSTEM
  • Surface guided radiotherapy
  • THERAPY

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