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

Abstract

Purpose: To investigate the dosimetric characteristics of the new GMS BT-125-1 125I radioactive seed, including dose rate constant, radial dose functions, and anisotropy functions. Methods: Dosimetric parameters of GMS BT-125-1 125I 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 125I, and model 6711 125I seeds. Results: The dose rate constant of GMS BT-125-1 125I seed was 0.959 cGy·h-1·U-1, with the difference of 0.94%, 0.83%, and 0.73% compared with the PharmaSeed BT-125-1 125I seed, PharmaSeed BT-125-2 125I seed, and Model 6711 125I 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 125I seed were found in agreement (within 3.3%) with corresponding results for the PharmaSeed BT-125-2 125I seed. The largest differences were 8.1% and 6.2% compared with PharmaSeed BT-125-1 125I seed and model 6711 125I seed, respectively. For anisotropy function, the difference between GMS BT-125-1 125I seed and PharmaSeed BT-125-2 125I seed was typically <10%. Conclusions: The measured dose rate constant, radial dose functions, and two-dimensional anisotropy functions for the GMS BT-125-1 125I seed showed good agreement with the Monte Carlo results. The dose rate constant of the GMS BT-125-1 125I seed is similar to that of the PharmaSeed BT-125-1 125I seed, the PharmaSeed BT-125-2 125I seed, and the model 6711 125I seed. For radial dose functions and two-dimensional anisotropy functions, the GMS BT-125-1 125I seed is similar to the PharmaSeed BT-125-2 125I seed but different from the PharmaSeed BT-125-1 125I seed and the model 6711 125I seed.