title: Theoretical substantiation of biological efficacy enhancement for β-delayed particle decay (9)C beam: A Monte Carlo study in combination with analysis with the local effect model approach.
abstract: OBJECTIVE
  To improve the efficacy of heavy ion therapy, β-delayed particle decay (9)C beam as a double irradiation source for cancer therapy has been proposed. The authors' previous experiment showed that relative biological effectiveness (RBE) values at the depths around the Bragg peak of a (9)C beam were enhanced and compared to its stable counterpart (12)C beam. The purpose of this study was to explore the nature of the biological efficacy enhancement theoretically.
  
  
  METHODS
  A Monte Carlo simulation study was conducted in this study. First a simplified cell model was established so as to form a tumor tissue. Subsequently, the tumor tissue was imported into the Monte Carlo simulation software package gate and then the tumor cells were virtually irradiated with comparable (9)C and (12)C beams, respectively, in the simulations. The transportation and particle deposition data of the (9)C and (12)C beams, derived from the gate simulations, were analyzed with the authors' local effect model implementation so as to deduce cell survival fractions.
  
  
  RESULTS
  The particles emitted from the decay process of deposited (9)C particles around a cell nucleus increased the dose delivered to the nucleus and elicited clustered damages around the secondary particles' trajectories. Therefore, compared to the (12)C beam, the RBE value of the (9)C beam increased at the depths around their Bragg peaks.
  
  
  CONCLUSIONS
  Collectively, the increased local doses and clustered damages due to the decayed particles emitted from deposited (9)C particles led to the RBE enhancement in contrast with the (12)C beam. Thus, the enhanced RBE effect of a (9)C beam for a simplified tumor model was shown theoretically in this study.
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China; and School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Liheng
authors.initials: L
authors.lastname: Tian
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, China and Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, China and Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China.
authors.forename: Xinguo
authors.initials: X
authors.lastname: Liu
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, China and Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China.
authors.forename: Zhongying
authors.initials: Z
authors.lastname: Dai
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, China and Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China.
authors.forename: Tingyan
authors.initials: T
authors.lastname: Fu
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, China and Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China.
authors.forename: Pengbo
authors.initials: P
authors.lastname: He
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China; and School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yuanlin
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China; and School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73000, China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Science, Lanzhou 730000, China; and School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Qiyan
authors.initials: Q
authors.lastname: Huang
mesh_terms: D000465:Algorithms; D001610:Beta Particles / Q000627:therapeutic use*; D009010:Monte Carlo Method; D012062:Relative Biological Effectiveness