title: Effect of photon beam energy, gold nanoparticle size and concentration on the dose enhancement in radiation therapy.
abstract: BACKGROUND
  Gold nanoparticles have been used as radiation dose enhancing materials in recent investigations. In the current study, dose enhancement effect of gold nanoparticles on tumor cells was evaluated using Monte Carlo (MC) simulation.
  
  
  METHODS
  We used MCNPX code for MC modeling in the current study. A water phantom and a tumor region with a size of 1×1×1 cm3 loaded with gold nanoparticles were simulated. The macroscopic dose enhancement factor was calculated for gold nanoparticles with sizes of 30, 50, and 100 nm. Also, we simulated different photon beams including mono-energetic beams (50-120 keV), a Cobalt-60 beam, 6 & 18 MV photon beams of a conventional linear accelerator.
  
  
  RESULTS
  We found a dose enhancement factor (DEF) of from 1.4 to 3.7 for monoenergetic kilovoltage beams, while the DEFs for megavoltage beams were negligible and less than 3% for all GNP sizes and concentrations. The optimum energy for higher DEF was found to be the 90 keV monoenergetic beam. The effect of GNP size was not considerable, but the GNP concentration had a substantial impact on achieved DEF in GNP-based radiation therapy.
  
  
  CONCLUSIONS
  The results were in close agreement with some previous studies considering the effect of photon energy and GNP concentration on observed DEF. Application of GNP-based radiation therapy using kilovoltage beams is recommended.
authors.affiliation: Medical Physics Department, Faculty of Medicine, Tabriz University of Medical sciences, Tabriz, Iran ; Radiation Oncology Department, Imam Hospital, Tabriz, Iran.
authors.forename: Asghar
authors.initials: A
authors.lastname: Mesbahi
authors.forename: Farideh
authors.initials: F
authors.lastname: Jamali
authors.forename: Nahideh
authors.initials: N
authors.lastname: Garehaghaji
keywords: Gold nanopa Dose enhancement factor; Gold nanoparticle (GNP); Monte Carlo method; Radiation therapy