ABSTRACT
Background: One of the ways to treat prostate cancer is brachytherapy using low-energy sources, such as iodine-125 [125I]. The purpose of this study was to assess dose enhancement factor in tumors in the presence of various nanoparticles in prostate tumor, and the effect of these nanoparticles on isodose curves in prostate cancer brachytherapy using Monte Carlo simulation.
Materials and Method: 125I brachytherapy source model SL- 125/SH-125 was simulated using Monte Carlo MCNPX code. TG- 43 parameters were calculated and verified. Dose enhancement factors were evaluated in presence of Fe2O3, Ag, Gd, Pt and Au nanoparticles in central cross section of the tumor in concentrations of 7, 18 and 30 mg/ml.
Results: Dose rate constant obtained 0.954 cGyh-1U-1. Maximum dose enhancement factors for Fe2O3, Ag, Gd, Pt and Au were 1.79, 1.32, 1.14, 1.15 and 1.27, respectively. Also, the 100% isodose line shifted toward the central point of the spherical tumor and the 100% isodose line shifted outward. Dose enhancement factors had no rule in increasing or decreasing by atomic number of nanoparticles.
Conclusion: Regarding to the simulation results, it can be concluded that nanoparticles presence in tumor leads to dose increase inside the tumor and dose decrease outside the tumor. Therefore, we can reduce treatment time and activity. So, the clinical use of these nanoparticles is recommended to enhance prostate brachytherapy dose.
ABSTRACT
Background: The aim of this study is to assess of dose enhancement effect in tumour in presence of 10B, 157Gd, 10B nanoparticles and 157Gd nanoparticles in radiotherapy through neutron capture by Monte Carlo method.
Materials and Methods: A 252Cf brachytherapy source AT model was simulated by Monte Carlo method code MCNPX and its TG-43 parameters were calculated and compared with previous corresponding data. This 252Cf brachytherapy source was used as a neutron source in neutron capture therapy. Dose enhancement factor was compared in tumour in presence of 10B, 157Gd, 10B nanoparticles and 157Gd nanoparticles for the concentrations of 100, 200 and 500 ppm of each capture agents in neutron capture. For this aim, around the 252Cf source, a spherical soft tissue phantom and a tumour containing each capture agents were considered.
Results: Calculated air kerma strength and dose rate constant for 252Cf source equals to 0.306 cGycm2/hµg and 5.782 cGy/Uh respectively. Among examined agents, maximum DEF belonged to 10B and 10B nanoparticles in concentration of 500 ppm. These values were reported as 1.06 and 1.08 respectively.
Conclusion: IN this study, air kerma strength and dose rate constant indicate difference of %7.27 and %1.10 with other corresponding values. In dose enhancement point of view, capture agents containing 10B are more useful in neutron capture therapy. In the same concentrations, dose enhancement factor for capture agents in nanoparticles form is higher than the presence of capture agents in atomic form. So, it is preferable to use of nanoparticle capture agent rather than atomic form. However, it should be noted that before clinical usage of this agents, other medical, chemical and physical criteria should be considered, for their comparison, in selection of capture agents in neutron capture therapy.