title: Monte Carlo simulations of ³He ion physical characteristics in a water phantom and evaluation of radiobiological effectiveness.
abstract: OBJECTIVE
  (3)He ions may hold great potential for clinical therapy because of both their physical and biological properties. In this study, the authors investigated the physical properties, i.e., the depth-dose curves from primary and secondary particles, and the energy distributions of helium ((3)He) ions. A relative biological effectiveness (RBE) model was applied to assess the biological effectiveness on survival of multiple cell lines.
  
  
  METHODS
  In light of the lack of experimental measurements and cross sections, the authors used Monte Carlo methods to study the energy deposition of (3)He ions. The transport of (3)He ions in water was simulated by using three Monte Carlo codes-FLUKA, GEANT4, and MCNPX-for incident beams with Gaussian energy distributions with average energies of 527 and 699 MeV and a full width at half maximum of 3.3 MeV in both cases. The RBE of each was evaluated by using the repair-misrepair-fixation model. In all of the simulations with each of the three Monte Carlo codes, the same geometry and primary beam parameters were used.
  
  
  RESULTS
  Energy deposition as a function of depth and energy spectra with high resolution was calculated on the central axis of the beam. Secondary proton dose from the primary (3)He beams was predicted quite differently by the three Monte Carlo systems. The predictions differed by as much as a factor of 2. Microdosimetric parameters such as dose mean lineal energy (y(D)), frequency mean lineal energy (y(F)), and frequency mean specific energy (z(F)) were used to characterize the radiation beam quality at four depths of the Bragg curve. Calculated RBE values were close to 1 at the entrance, reached on average 1.8 and 1.6 for prostate and head and neck cancer cell lines at the Bragg peak for both energies, but showed some variations between the different Monte Carlo codes.
  
  
  CONCLUSIONS
  Although the Monte Carlo codes provided different results in energy deposition and especially in secondary particle production (most of the differences between the three codes were observed close to the Bragg peak, where the energy spectrum broadens), the results in terms of RBE were generally similar.
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Houston, Texas 77030.
authors: Reza
authors: R
authors: Taleei
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Houston, Texas 77030.
authors: Fada
authors: F
authors: Guan
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Houston, Texas 77030.
authors: Chris
authors: C
authors: Peeler
authors: Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030.
authors: Lawrence
authors: L
authors: Bronk
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Houston, Texas 77030.
authors: Darshana
authors: D
authors: Patel
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Houston, Texas 77030.
authors: Dragan
authors: D
authors: Mirkovic
authors: Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Houston, Texas 77030.
authors: David R
authors: DR
authors: Grosshans
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Houston, Texas 77030.
authors: Radhe
authors: R
authors: Mohan
authors: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Houston, Texas 77030.
authors: Uwe
authors: U
authors: Titt
mesh_terms: D016923:Cell Death; D006371:Helium / Q000627:therapeutic use*; D007554:Isotopes; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D012062:Relative Biological Effectiveness; D014867:Water
chemical_list: D007554:Isotopes; D014867:Water; D006371:Helium