Dosimetric characterization of GMS BT ‐125‐1 125 I radioactive seed with Monte Carlo simulations and experimental measurement

Purpose To investigate the dosimetric characteristics of the new GMS BT ‐125‐1 125 I radioactive seed, including dose rate constant, radial dose functions, and anisotropy functions. Methods Dosimetric parameters of GMS BT ‐125‐1 125 I seed including dose rate constant, radial dose functions, and anisotropy functions were calculated using the Monte Carlo code of MCNP 5, and measured with thermoluminescent dosimeters ( TLD s). The results were compared with those of PharmaSeed BT ‐125‐1, PharmaSeed BT ‐125‐2 125 I, and model 6711 125 I seeds. Results The dose rate constant of GMS BT ‐125‐1 125 I seed was 0.959 c G y · h − 1 · U − 1, with the difference of 0.94%, 0.83%, and 0.73% compared with the PharmaSeed BT ‐125‐1 125 I seed, PharmaSeed BT ‐125‐2 125 I seed, and Model 6711 125 I seed, respectively. For radial dose function, the differences between the Monte Carlo and the experimental g ( r ) results were mostly within 10%. Monte Carlo results of g ( r ) for GMS BT ‐125‐1 125 I seed were found in agreement (within 3.3%) with corresponding results for the PharmaSeed BT ‐125‐2 125 I seed. The largest differences were 8.1% and 6.2% compared with PharmaSeed BT ‐125‐1 125 I seed and model 6711 125 I seed, respectively. For anisotropy function, the difference between GMS BT ‐125‐1 125 I seed and PharmaSeed BT ‐125‐2 125 I seed was typically <10%. Conclusions The measured dose rate constant, radial dose functions, and two‐dimensional anisotropy functions for the GMS BT ‐125‐1 125 I seed showed good agreement with the Monte Carlo results. The dose rate constant of the GMS BT ‐125‐1 125 I seed is similar to that of the PharmaSeed BT ‐125‐1 125 I seed, the PharmaSeed BT ‐125‐2 125 I seed, and the model 6711 125 I seed. For radial dose functions and two‐dimensional anisotropy functions, the GMS BT ‐125‐1 125 I seed is similar to the PharmaSeed BT ‐125‐2 125 I seed but different from the PharmaSeed BT ‐125‐1 125 I seed and the model 6711 125 I seed.