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 MCNP5, and measured with thermoluminescent dosimeters (TLDs). 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 [Formula: see text] , 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.