Monte carlo-aided dosimetry of the new Bebig IsoSeed (R) Pd-103 interstitial brachytherapy seed

A new model Pd-103 interstitial brachytherapy source, the IsoSeed((R)) Pd-1 03, was recently introduced by Bebig Isotopentechnik und Umweltdiagnostik G mbH for permanent implant applications. This study presents the first quant itative theoretical study of the seed's dosimetric quantities. Monte Carlo photon transport (MCPT) simulation techniques have been used to evaluate th e dose-rate distributions around the model IsoSeed((R)) Pd-103 source in li quid water and air phantoms. These results have been used to calculate and tabulate the anisotropy function, F(r, theta), radial dose function, g(r), and anisotropy factors, phi (r), and dose-rate constant as defined by AAPM Task Group 43 (TG-43) Report. Cartesian "away" and "along" tables, giving t he dose rates per unit air-kerma strength in water in the range 0.1-3 cm di stance around the seed have also been tabulated. The dose-rate constant, A, was evaluated by simulating the wide-angle, free-air chamber (WAFAC) calib ration geometry recently implemented by NIST (National Institute of Standar ds and Technology) to realize the primary standard of air-kerma strength (S -K,S-N99) for low-energy photon-emitting brachytherapy sources. The dose-ra te constant has been found to be Lambda =0.660 +/-0.017 in units of dose-ra te per unit air-kerma strength (cGy.h(-1.)U(-1)). (C) 2001 American Associa tion of Physicists in Medicine.