Efficacy of various nanoparticle types in dose enhancement during low energy X-ray IORT: A Monte Carlo simulation study

Abstract

One of the main limitations during low-kV IORT (intraoperative radiotherapy) with dedicated spherical applicators is the long treatment time. Employing nanoparticles (NPs) can reduce the treatment time through increasing the absorbed dose by the irradiated volume. The current study aims to evaluate and compare the efficacy of different clinically recommended NP types in dose enhancement during low-kV IORT using a Monte Carlo simulation approach.The INTRABEAM, a dedicated IORT machine, including the bare probe along with 2 and 4 cm diameter spherical applicators was simulated by MCNPX Monte Carlo code and dose enhancement factor (DEF) in presence of eight different NP types of Silver (Ag), Gold (Au), Bismuth (Bi), Iron (Fe), Gadolinium (Gd), Hafnium (Hf), Platinum (Pt), and Titanium (Ti) with two concentrations of 0.5% (5 mg/g) and 2% (20 mg/g) were calculated inside the water.The results demonstrated that the Bi nanoparticle has the most desirable efficacy in dose enhancement within the target region as well as protection of underlying healthy tissues, especially at 2% concentration. Ag, Au, Hf, and Pt NPs have also a good performance in dose enhancement within the tumor volume, but at expense of higher absorbed dose by underlying healthy tissues.From the results, it can be concluded that employing the NPs during low energy X-ray IORT can considerably reduce the treatment time, a fact that can increase the lifetime of the IORT machine as well as improve the anesthetized patient manipulation irradiated inside the operating room.