Z . Mehrabankhoo et al .: Radioprotection 2024 , 59 ( 1 ), 19 – 25 23 Fig . 4 . Relative difference of the absorbed dose data between the 95 th percentile and the reported results for VIPMAN by Bozkurt et al ( MCNP4B ) and McHale et al . ( MCNP6.2 ) in AP lungs ( a ), PA thyroid ( b ), ISO stomach ( c ), and ROT liver ( d ).
geometries . The lungs , liver , and spleen agree with the results of VIPMAN in all geometries except for the ISO heart at energies 1 , 3 , and 5MeV and the RLAT lungs . The stomach of the 95 th percentile receives significantly lower dose when irradiated from the right side due to the longer travel distance of neutrons . Conversely , the liver showed this trend when irradiated from the left side . Generally , there is a better agreement between the data of the two phantoms at energies above 1 MeV compared to energies below 1 MeV in all geometries for most organs .
In this study , the absorbed dose data reported by Bozkurt et al . ( 2000 ) were used for comparisons . In Bozkurt et al ’ s study , all organs absorbed doses necessary to calculate the effective dose were available . The effective dose was obtained based on the same w T , w R , and calculation method in this study . It is worth noting that Bozkurt et al . used the MCNP4B Monte
Carlo code for their calculations , while in this study , MCNPX2.6 was used . Differences in MCNP versions may introduce variations in the data . To investigate the impact of MCNP version differences , the 95 th percentile data were also compared with the new organ absorbed dose of VIPMAN recently reported by McHale et al . using MCNP6.2 ( McHale and Walker , 2021 ). In McHale ’ s study , a limited number of organs absorbed doses were tabulated , so it was impossible to calculate the effective dose based on this data . Figures 4a to 4d illustrate the relative difference between the 95 th percentile data with the data from Bozkurt et al and McHale et al . for AP lungs , PA thyroid , ISO stomach , and ROT liver , respectively . Similarities between the data , especially in the AP geometry , are observed in these figures . However , for ISO and ROT geometries , the difference is significant , with deviations of about 20 % or more .