Dose distribution analysis for seed implant models 125I and 103Pd in prostate brachytherapy using MCNPX simulation

Prostate cancer brachytherapy is performed by illuminating a radioactive source that emits gamma radiation into the prostate organ.The organs around the prostate are at risk of being exposed to this radiation, and the radiation dose received by these organs must be lower than the predetermined dose percentage.This study aims to obtain the most effective 125I and 103Pd seed placement models for prostate cancer brachytherapy and to analyze the distribution of doses to the target prostate volume and organs at risk.The MCNPX simulation method was used for prostate cancer brachytherapy to simulate the coordinates of seed placement and dose distribution.The ORNL-MIRD phantom geometry was obtained from a program listing variations in seed types and coordinates, 125I and 103Pd as radiation sources with activities of 0.6 and 1.4 mCi.The calculation results show that the dose value in the model reference and model modification differs for each type of radiation source.In the Lazarine model, the prostate-absorbed doses of 125I and 103Pd were 106.04 and 102.22 Gy, respectively.In the modified model, the absorbed dose values of 125I and 103Pd are 100.14 and 113.44 Gy.The 103Pd source is lower than the 125I source for organ absorption at risk, but the dose received by both OAR sources is relatively safe.The modified seed placement model is more effective for 103Pd radiation sources but still adequate with 125I sources.The modified seed placement model effectively uses 125I and 103Pd radiation sources because the effective dose received by the prostate and OAR have relatively the same value.