Dose enhancement by various nanoparticles in prostate brachytherapy.

The aim of this Monte Carlo study is to calculate dose enhancement in tumours by various nanoparticles in prostate brachytherapy using (125)I interstitial implants. ProstaSeed (125)I brachytherapy source was simulated using MCNPX Monte Carlo code. Dose rate constant, radial dose function and anisotropy function values were calculated and compared with previously published data. Dose enhancement factors (DEFs) were calculated for Fe2O3, Ag, Gd, Pt and Au nanoparticles with concentrations of 7, 18 and 30 mg/ml. Our source simulation was validated by comparing our results with previously published data. Maximum DEF values on the central transverse line, within the tumour, for Fe2O3, Ag, Gd, Pt and Au nanoparticles with 30 mg/ml concentration were 1.27, 1.15, 1.14, 1.32, 1.79, respectively. No general trend in DEF with increasing atomic number, or concentration of nanoparticles was observed. However, DEF was the highest for 30 mg/ml concentration of Au. The 50 % isodose line tightened toward the central point of the spherical tumour and the central 100 % isodose line expanded outward. The presence of nanoparticles in a prostate tumour increases the dose inside tumour and decreases the dose outside it, thus the treatment time and source activity can be decreased due to dose enhancement in the tumour. While more preclinical studies on other aspects are necessary, using nanoparticles can be proposed as a useful tool in prostate brachytherapy. Au nanoparticles with higher concentrations can be more useful for this purpose when compared to other nanoparticles.