Four-dimensional lung treatment planning in layer-stacking carbon ion beam treatment: Comparison of layer-stacking and conventional ungated/gated irradiation

Shinichiro Mori, Nobuyuki Kanematsu, Hiroshi Asakura, Gregory C. Sharp, Motoki Kumagai, Suguru Dobashi, Mio Nakajima, Naoyoshi Yamamoto, Susumu Kandatsu, Masayuki Baba

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Purpose: We compared four-dimensional (4D) layer-stacking and conventional carbon ion beam distribution in the treatment of lung cancer between ungated and gated respiratory strategies using 4DCT data sets. Methods and Materials: Twenty lung patients underwent 4DCT imaging under free-breathing conditions. Using planning target volumes (PTVs) at respective respiratory phases, two types of compensating bolus were designed, a full single respiratory cycle for the ungated strategy and an approximately 30% duty cycle for the exhalation-gated strategy. Beams were delivered to the PTVs for the ungated and gated strategies, PTV(ungated) and PTV(gated), respectively, which were calculated by combining the respective PTV(Tn)s by layer-stacking and conventional irradiation. Carbon ion beam dose distribution was calculated as a function of respiratory phase by applying a compensating bolus to 4DCT. Accumulated dose distributions were calculated by applying deformable registration. Results: With the ungated strategy, accumulated dose distributions were satisfactorily provided to the PTV, with D95 values for layer-stacking and conventional irradiation of 94.0% and 96.2%, respectively. V20 for the lung and Dmax for the spinal cord were lower with layer-stacking than with conventional irradiation, whereas Dmax for the skin (14.1 GyE) was significantly lower (21.9 GyE). In addition, dose conformation to the GTV/PTV with layer-stacking irradiation was better with the gated than with the ungated strategy. Conclusions: Gated layer-stacking irradiation allows the delivery of a carbon ion beam to a moving target without significant degradation of dose conformity or the development of hot spots.

Original languageEnglish
Pages (from-to)597-607
Number of pages11
JournalInternational Journal of Radiation Oncology Biology Physics
Volume80
Issue number2
DOIs
Publication statusPublished - 2011 Jun 1
Externally publishedYes

Keywords

  • CT
  • Carbon ion beam
  • Four-dimensional
  • Layer-stacking
  • Lung
  • Treatment planning

ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

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