title: A comparison study on various low energy sources in interstitial prostate brachytherapy.
abstract: OBJECTIVE
  Low energy sources are routinely used in prostate brachytherapy. (125)I is one of the most commonly used sources. Low energy (131)Cs source was introduced recently as a brachytherapy source. The aim of this study is to compare dose distributions of (125)I, (103)Pd, and (131)Cs sources in interstitial brachytherapy of prostate.
  
  
  METHODS
  ProstaSeed (125)I brachytherapy source was simulated using MCNPX Monte Carlo code. Additionally, two hypothetical sources of (103)Pd and (131)Cs were simulated with the same geometry as the ProstaSeed (125)I source, while having their specific emitted gamma spectra. These brachytherapy sources were simulated with distribution of forty-eight seeds in a phantom including prostate. The prostate was considered as a sphere with radius of 1.5 cm. Absolute and relative dose rates were obtained in various distances from the source along the transverse and longitudinal axes inside and outside the tumor. Furthermore, isodose curves were plotted around the sources.
  
  
  RESULTS
  Analyzing the initial dose profiles for various sources indicated that with the same time duration and air kerma strength, (131)Cs delivers higher dose to tumor. However, relative dose rate inside the tumor is higher and outside the tumor is lower for the (103)Pd source.
  
  
  CONCLUSIONS
  The higher initial absolute dose in cGy/(h.U) of (131)Cs brachytherapy source is an advantage of this source over the others. The higher relative dose inside the tumor and lower relative dose outside the tumor for the (103)Pd source are advantages of this later brachytherapy source. Based on the total dose the (125)I source has advantage over the others due to its longer half-life.
authors.affiliation: Faculty of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Bakhshabadi
authors.affiliation: Medical Physics Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Ghorbani
authors.affiliation: Faculty of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Khosroabadi
authors.affiliation: Comprehensive Cancer Centers of Nevada, Las Vegas, Nevada, USA.
authors.forename: Courtney
authors.initials: C
authors.lastname: Knaup
authors.affiliation: Comprehensive Cancer Centers of Nevada, Las Vegas, Nevada, USA.
authors.forename: Ali S
authors.initials: AS
authors.lastname: Meigooni
keywords: 103Pd; 125I; 131Cs; Monte Carlo simulation; prostate brachytherapy; prostate cancer