title: Monte Carlo Determination of Dosimetric Parameters of a New (125)I Brachytherapy Source According to AAPM TG-43 (U1) Protocol.
abstract: BACKGROUND
  (125)I is one of the important sources frequently used in brachytherapy. Up to now, several different commercial models of this source type have been introduced to the clinical radiation oncology applications. Recently, a new source model, IrSeed-125, has been added to this list. The aim of the present study is to determine the dosimetric parameters of this new source model based on the recommendations of TG-43 (U1) protocol using Monte Carlo simulation.
  
  
  METHODS
  The dosimetric characteristics of Ir-125 including dose rate constant, radial dose function, 2D anisotropy function and 1D anisotropy function were determined inside liquid water using MCNPX code and compared to those of other commercially available iodine sources.
  
  
  RESULTS
  The dose rate constant of this new source was found to be 0.983+0.015 cGyh-1U-1 that was in good agreement with the TLD measured data (0.965 cGyh-1U-1). The 1D anisotropy function at 3, 5, and 7 cm radial distances were obtained as 0.954, 0.953 and 0.959, respectively.
  
  
  CONCLUSIONS
  The results of this study showed that the dosimetric characteristics of this new brachytherapy source are comparable with those of other commercially available sources. Furthermore, the simulated parameters were in accordance with the previously measured ones. Therefore, the Monte Carlo calculated dosimetric parameters could be employed to obtain the dose distribution around this new brachytherapy source based on TG-43 (U1) protocol.
authors.affiliation: Radiation Medicine Department, Shahid Beheshti University, Tehran, Iran, Physics Department, Hakim Sabzevari University, Sabzevar, Iran. hamidreza.baghani@gmail.com.
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Baghani
authors.affiliation: Medical Physics Department, Ilam University of Medical Science, Ilam, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Lohrabian
authors.affiliation: Radiation Medicine Department, Shahid Beheshti University, Tehran, Iran.
authors.forename: Mahmoud Reza
authors.initials: MR
authors.lastname: Aghamiri
authors.affiliation: Medical Physics Department, Tehran University of Medical Science, Tehran, Iran.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Robatjazi
mesh_terms: D016880:Anisotropy; D001918:Brachytherapy / Q000592:standards*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D009010:Monte Carlo Method; D009369:Neoplasms / Q000532:radiotherapy*; D017410:Practice Guidelines as Topic; D011874:Radiometry / Q000379:methods*
chemical_list: D007457:Iodine Radioisotopes