Optimization of Internal Margin to Account for Dosimetric Effects of Respiratory Motion

Yildirim D. Mutaf, Debra H Brinkmann

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Purpose: Use of internal margins to account for respiratory motion of the target volumes is a common strategy in radiotherapy of mobile tumors. Although efficient for tumor coverage, this expansion also risks increased toxicity to nearby healthy organs and therefore requires a careful selection of appropriate margins. In this study, we demonstrate an optimization of the internal margin used to account for respiration motion. Methods and Materials: Three-dimensional conformal treatment plans for phantom spherical target volumes as well as clinical treatment plans of 11 patients were evaluated retrospectively for optimum internal margin selection. A software-based simulation of respiration motion was performed for all cases. Moreover, the interplay with treatment setup uncertainties and corresponding margins was investigated in the phantom study. Results: Optimum internal margins in both phantom and patient studies were found to be substantially smaller than the actual target displacement due to respiration. The optimal internal margin was also observed to be approximately independent of the setup margins. Furthermore, no statistically significant dependence on target size and shape was observed in the group of 11 patients. Conclusions: These findings present significant implications for treatment planning of mobile targets, such as tumors found in the lung and upper abdomen. We conclude that the full motion amplitude for the internal margin is overly conservative, and optimization of the internal margin provides improved sparing of nearby organs at risk without sacrificing dosimetric coverage for the target.

Original languageEnglish (US)
Pages (from-to)1561-1570
Number of pages10
JournalInternational Journal of Radiation Oncology Biology Physics
Volume70
Issue number5
DOIs
StatePublished - Apr 1 2008

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margins
Respiration
optimization
Organs at Risk
respiration
Neoplasms
Therapeutics
tumors
Abdomen
Uncertainty
Radiotherapy
Software
organs
Lung
abdomen
toxicity
lungs
planning
radiation therapy
computer programs

Keywords

  • Internal margin
  • Internal target volume
  • Intrafractional motion
  • Respiration

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation

Cite this

Optimization of Internal Margin to Account for Dosimetric Effects of Respiratory Motion. / Mutaf, Yildirim D.; Brinkmann, Debra H.

In: International Journal of Radiation Oncology Biology Physics, Vol. 70, No. 5, 01.04.2008, p. 1561-1570.

Research output: Contribution to journalArticle

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