title: Effect of tissue composition on dose distribution in electron beam radiotherapy.
abstract: OBJECTIVE
  The aim of this study is to evaluate the effect of tissue composition on dose distribution in electron beam radiotherapy.
  
  
  METHODS
  A Siemens Primus linear accelerator and a phantom were simulated using MCNPX Monte Carlo code. In a homogeneous cylindrical phantom, six types of soft tissue and three types of tissue-equivalent materials were investigated. The tissues included muscle (skeletal), adipose tissue, blood (whole), breast tissue, soft tissue (9-components) and soft tissue (4-component). The tissue-equivalent materials were water, A-150 tissue-equivalent plastic and perspex. Electron dose relative to dose in 9-component soft tissue at various depths on the beam's central axis was determined for 8, 12, and 14 MeV electron energies.
  
  
  RESULTS
  The results of relative electron dose in various materials relative to dose in 9-component soft tissue were reported for 8, 12 and 14 MeV electron beams as tabulated data. While differences were observed between dose distributions in various soft tissues and tissue-equivalent materials, which vary with the composition of material, electron energy and depth in phantom, they can be ignored due to the incorporated uncertainties in Monte Carlo calculations.
  
  
  CONCLUSIONS
  Based on the calculations performed, differences in dose distributions in various soft tissues and tissue-equivalent materials are not significant. However, due to the difference in composition of various materials, further research in this field with lower uncertainties is recommended.
authors.affiliation: Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran;
authors.forename: M
authors.initials: M
authors.lastname: Ghorbani
authors.affiliation: Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran;
authors.forename: Z S
authors.initials: ZS
authors.lastname: Tabatabaei
authors.affiliation: Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran;
authors.forename: A
authors.initials: A
authors.lastname: Vejdani Noghreiyan
authors.affiliation: Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran;
authors.forename: H
authors.initials: H
authors.lastname: Vosoughi
authors.affiliation: Comprehensive Cancer Centers of Nevada, Las Vegas, Nevada, USA;
authors.forename: C
authors.initials: C
authors.lastname: Knaup
keywords: Electron Mode; Linear Accelerator; Monte Carlo Simulation; Soft Tissue; Tissue-equivalent Materials