title: Tissue composition effect on dose distribution in neutron brachytherapy/neutron capture therapy.
abstract: OBJECTIVE
  The aim of this study is to assess the effect of the compositions of various soft tissues and tissue-equivalent materials on dose distribution in neutron brachytherapy/neutron capture therapy.
  
  
  BACKGROUND
  Neutron brachytherapy and neutron capture therapy are two common radiotherapy modalities.
  
  
  METHODS
  Dose distributions were calculated around a low dose rate (252)Cf source located in a spherical phantom with radius of 20.0 cm using the MCNPX code for seven soft tissues and three tissue-equivalent materials. Relative total dose rate, relative neutron dose rate, total dose rate, and neutron dose rate were calculated for each material. These values were determined at various radial distances ranging from 0.3 to 15.0 cm from the source.
  
  
  RESULTS
  Among the soft tissues and tissue-equivalent materials studied, adipose tissue and plexiglass demonstrated the greatest differences for total dose rate compared to 9-component soft tissue. The difference in dose rate with respect to 9-component soft tissue varied with compositions of the materials and the radial distance from the source. Furthermore, the total dose rate in water was different from that in 9-component soft tissue.
  
  
  CONCLUSIONS
  Taking the same composition for various soft tissues and tissue-equivalent media can lead to error in treatment planning in neutron brachytherapy/neutron capture therapy. Since the International Commission on Radiation Units and Measurements (ICRU) recommends that the total dosimetric uncertainty in dose delivery in radiotherapy should be within ±5%, the compositions of various soft tissues and tissue-equivalent materials should be considered in dose calculation and treatment planning in neutron brachytherapy/neutron capture therapy.
authors.affiliation: Faculty of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Khosroabadi
authors.affiliation: Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Bagher
authors.initials: B
authors.lastname: Farhood
authors.affiliation: Medical Physics Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Ghorbani
authors.affiliation: Medical Physics Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Nima
authors.initials: N
authors.lastname: Hamzian
authors.affiliation: Faculty of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran.
authors.forename: Homa Rezaei
authors.initials: HR
authors.lastname: Moghaddam
authors.affiliation: Comprehensive Cancer Centers of Nevada, Las Vegas, Nevada, USA.
authors.forename: David
authors.initials: D
authors.lastname: Davenport
keywords: 252Cf; Dose rate; Neutron brachytherapy; Neutron capture therapy; Tissue composition