An inter-comparison between MCNPX and EGSnrc Monte Carlo codes in grid radiotherapy characterization using beta-emitting radionuclides

Abstract

IntroductionThe applicability of MCNPX and EGSnrc Monte Carlo codes in dosimetric characterization of spatially fractionated radiotherapy (SFRT or grid radiotherapy, in other words) of superficial tumors using beta-emitting radionuclides has been assessed in the current study. Materials and methodsA grid block including 63 cubic holes was modeled by each Monte Carlo code. Then, the grid block was separately filled by four widely adopted beta-emitting radioisotopes for radionuclide-therapy purposes including 32P, 90Y, 166Ho, and 188Re. Finally, the depth dose distribution and transverse dose profiles at different depths were separately calculated for each radionuclide using both MCNPX and EGSnrc Monte Carlo codes. Obtained results were quantitatively compared by gamma analysis as well as an R-squared statistical test to evaluate the compatibility of acquired dosimetry results by each code. ResultsSimilar dosimetry results were obtained by both Monte Carlo codes, where no significant difference was observed among the obtained data by each code. The uniformity of dose distribution improved with increasing the depth inside the phantom for all radionuclides under investigation. ConclusionFrom the results, it can be concluded that MCNPX and EGSnrc Monte Carlo codes have similar performance in dosimetric characterization of grid radiotherapy using beta-emitting radionuclides. Small differences between the results acquired by employed codes originate from associated statistical uncertainty with the Monte Carlo data as well as differences in considered condense history scheme (CHS) during the electron transport inside the medium.