Comprehensive Monte Carlo calculations of AAPM Task Group Report No. 43 dosimetry parameters for the Model 3500 I-Plant 125I brachytherapy source

The Model 3500 I-Plant 125I brachytherapy source, produced by Implant Sciences Corporation, is created through a novel technique which utilizes ion implantation of 124Xe into a ceramic matrix followed by neutron activation of the substrate. Clinical dosimetry parameters were calculated using MCNP. For data processing, a 0.376 cm active length was used for the geometry function. The 2-D anisotropy function, F(r,θ), exhibited less anisotropy than the Amersham Health Model 6711 source, and decreased as radial distance, r, increased. The anisotropy constant, image, was 0.933; dose rate constant, Λ, was 1.017±0.005 cGy/h/U; and radial dose function, g(r), for r={0.1, 0.2, 0.5, 2, 5, 10 cm} was 0.990, 1.014, 1.030, 0.872, 0.448, and 0.114, respectively. In general, there was good agreement with experimental results recently obtained by others using thermoluminescent dosimeters.