Dosimetric characteristic of a new 125I brachytherapy source

A new brachytherapy 125I source has been investigated at Iranian Agricultural, Medical and Industrial Research School. Dosimetric characteristics [dose-rate constant Λ, radial dose function gL(r) and anisotropy function F(r,θ] of IRA-125I were theoretically determined in terms of the updated AAPM task group 43 (TG-43U1) recommendations. Versions 5 and 4C of the Monte Carlo radiation transport code were used to calculate the dosimetry parameters around the source. The Monte Carlo calculated dose-rate constant of the 125I source in water was found to be 92 x 10-4 Gy h-1 U-1 with an approximate uncertainty of ±3 %. Brachytherapy seed model, 6711-125I, carrying 125I radionuclides, was modelled and benchmarked against previously published values. Finally, the calculated results were compared with the published results of those of other source manufacturers. (authors)